Daftar Isi
Here, I describe basic tips to configure and manage systems, mostly from the console.
There are some utility programs to help your console activities.
Tabel 9.1. List of programs to support console activities
paket | popcon | ukuran | deskripsi |
---|---|---|---|
mc
|
V:55, I:234 | 1492 | See Bagian 1.3, “Midnight Commander (MC)” |
bsdutils
|
V:708, I:999 | 394 | script command to make typescript of terminal session |
screen
|
V:114, I:283 | 1014 | terminal multiplexer with VT100/ANSI terminal emulation |
tmux
|
V:35, I:143 | 830 | terminal multiplexer alternative (Use "Control-B" instead) |
fzf
|
V:2, I:7 | 2637 | fuzzy text finder |
fzy
|
V:0, I:0 | 54 | fuzzy text finder |
rlwrap
|
V:1, I:20 | 297 | readline feature command line wrapper |
ledit
|
V:0, I:14 | 306 | readline feature command line wrapper |
rlfe
|
V:0, I:0 | 49 | readline feature command line wrapper |
The simple use of script
(1) (see Bagian 1.4.9, “Recording the shell activities”) to record shell activity
produces a file with control characters. This can be avoided by using
col
(1) as the following.
$ script Script started, file is typescript
Do whatever … and press Ctrl-D
to exit
script
.
$ col -bx < typescript > cleanedfile $ vim cleanedfile
There are alternative methods to record the shell activities:
Use tee
(usable during the boot process in the
initramfs):
$ sh -i 2>&1 | tee typescript
Use gnome-terminal
with the extend line buffer for
scrollback.
Use screen
with "^A H
" (see Bagian 9.1.2, “The screen program”) to perform recording of console.
Use vim
with ":terminal
" to enter the
terminal mode. Use "Ctrl-W N
" to exit from terminal mode
to normal mode. Use ":w typescript
" to write the buffer
to a file.
Use emacs
with "M-x shell
",
"M-x eshell
", or "M-x term
" to enter
recording console. Use "C-x C-w
" to write the buffer to
a file.
screen
(1) not only allows one terminal window to work
with multiple processes, but also allows remote
shell process to survive interrupted connections. Here is a
typical use scenario of screen
(1).
You login to a remote machine.
You start screen
on a single console.
You execute multiple programs in screen
windows created
with ^A c
("Control-A" followed by "c").
You switch among the multiple screen
windows by
^A n
("Control-A" followed by "n").
Suddenly you need to leave your terminal, but you don't want to lose your active work by keeping the connection.
You may detach the
screen
session by any methods.
Brutally unplug your network connection
Type ^A d
("Control-A" followed by "d") and manually
logging out from the remote connection
Type ^A DD
("Control-A" followed by "DD") to have
screen
detach and log you out
You log in again to the same remote machine (even from a different terminal).
You start screen
as "screen -r
".
screen
magically reattaches all previous screen
windows with all actively running programs.
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Tip |
---|---|
You can save connection fees with |
In a screen
session, all keyboard inputs are sent to your
current window except for the command keystroke. All
screen
command keystrokes are entered by typing
^A
("Control-A") plus a single key [plus any
parameters]. Here are important ones to remember.
Tabel 9.2. List of key bindings for screen
key binding | arti |
---|---|
^A ? |
show a help screen (display key bindings) |
^A c |
create a new window and switch to it |
^A n |
go to next window |
^A p |
go to previous window |
^A 0 |
go to window number 0 |
^A 1 |
go to window number 1 |
^A w |
show a list of windows |
^A a |
send a Ctrl-A to current window as keyboard input |
^A h |
write a hardcopy of current window to file |
^A H |
begin/end logging current window to file |
^A ^X |
lock the terminal (password protected) |
^A d |
detach screen session from the terminal |
^A DD |
detach screen session and log out |
See screen
(1) for details.
Lihat tmux
(1)untuk fungsionalitas dari perintah
alternatif.
In Bagian 1.4.2, “Customizing bash”, 2 tips to allow quick navigation
around directories are described: $CDPATH
and
mc
.
If you use fuzzy text filter program, you can do without typing the exact
path. For fzf
, include following in
~/.bashrc
.
FZF_KEYBINDINGS_PATH=/usr/share/doc/fzf/examples/key-bindings.bash if [ -f $FZF_KEYBINDINGS_PATH ]; then . $FZF_KEYBINDINGS_PATH fi FZF_COMPLETION_PATH=/usr/share/doc/fzf/examples/completion.bash if [ -f $FZF_COMPLETION_PATH ]; then . $FZF_COMPLETION_PATH fi
For example:
You can jump to a very deep subdirectory with minimal efforts. You first
type "cd **
" and press Tab
. Then you
will be prompted with candidate paths. Typing in partial path strings,
e.g., s/d/b foo
, will narrow down candidate paths. You
select the path to be used by cd
with cursor and return
keys.
You can select a command from the command history more efficiently with
minimal efforts. You press Ctrl-R
at the command
prompt. Then you will be prompted with candidate commands. Typing in
partial command strings, e.g., vim d
, will narrow down
candidates. You select the one to be used with cursor and return keys.
Some commands such as /usr/bin/dash
which lacks command
line history editing capability can add such functionality transparently by
running under rlwrap
or its equivalents.
$ rlwrap dash -i
This provides convenient platform to test subtle points for
dash
with friendly bash
-like
environment.
After you learn basics of vim
(1) through Bagian 1.4.8, “Using vim”, please read Bram Moolenaar's "Seven habits of effective text
editing (2000)" to understand how vim
should be
used.
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Perhatian |
---|---|
Don't try to change the default key bindings without very good reasons. |
The behavior of vim
can be changed significantly by
enabling its internal features through the Ex
-mode
commands such as "set ...
" to set vim options.
These Ex
-mode commands can be included in user's vimrc
file, traditional "~/.vimrc
" or git-friendly
"~/.vim/vimrc
". Here is a very simple example
[2]:
colorscheme murphy " from /usr/share/vim/vim??/colors/*.vim filetype plugin indent on " filetype aware behavior syntax enable " Syntax highlight "set spelllang=en_us " Spell check language as en_us "set spell " Enable spell check set autoindent " Copy indent from current line set smartindent " More than autoindent (Drop/Pop after {/}) set nosmarttab " <Tab>-key always inserts blanks set backspace=indent,eol,start " Back space through everything set laststatus=2 " Always show status line set statusline=%<%f%m%r%h%w%=%y[U+%04B]%2l/%2L=%P,%2c%V
Simple customization to enable securemodelines and classical IDE can be enabled by installing vim-scripts package and appending the following to user's vimrc file.
packadd! securemodelines packadd! winmanager let mapleader = ' ' " Toggle paste mode with <SPACE>p set pastetoggle=<leader>p " IDE-like UI for files and buffers with <space>w nnoremap <leader>w :WMToggle<CR> " Use safer keys <SPACE>? for moving to another window nnoremap <leader>h <C-W>h nnoremap <leader>j <C-W>j nnoremap <leader>k <C-W>k nnoremap <leader>l <C-W>l
The new native Vim package system works nicely with "git
"
and "git submodule
". One such example configuration can
be found at my git repository:
dot-vim. This does essentially:
By using "git
" and "git submodule
",
latest external packages, such as
"name
", are placed into
~/.vim/pack/*/opt/name
and similar.
By adding :packadd! name
line to
user's vimrc file, these packages are placed on
runtimepath
.
Vim loads these packages on runtimepath
during its
initialization.
At the end of its initialization, tags for the installed documents are
updated with "helptags ALL
".
For more, please start vim
with "vim
--startuptime vimstart.log
" to check actual execution sequence and
time spent for each step.
Interesting external plugin packages can be found:
Vim - the ubiquitous text editor -- The official upstream site of Vim and vim scripts
VimAwsome -- The listing of Vim plugins
vim-scripts -- Debian package: a collection of vim scripts
It is quite confusing to see too many ways[3] to manage and load these external packages to
vim
. Checking the original information is the best cure.
Tabel 9.3. Information on the initialization of vim
key strokes | information |
---|---|
:help package |
explanation on the vim package mechanism |
:help runtimepath |
explanation on the runtimepath mechanism |
:version |
internal states including candidates for the vimrc file |
:echo $VIM |
the environment variable "$VIM " used to locate the vimrc
file |
:set runtimepath? |
list of directories which will be searched for all runtime support files |
:echo $VIMRUNTIME |
the environment variable "$VIMRUNTIME " used to locate
various system provided runtime support files |
Many programs record their activities under the
"/var/log/
" directory.
See Bagian 3.4, “The system message” and Bagian 3.3, “The kernel message”.
Here are notable log analyzers
("~Gsecurity::log-analyzer
" in
aptitude
(8)).
Tabel 9.4. List of system log analyzers
paket | popcon | ukuran | deskripsi |
---|---|---|---|
logwatch
|
V:16, I:18 | 2265 | log analyzer with nice output written in Perl |
fail2ban
|
V:116, I:129 | 2092 | ban IPs that cause multiple authentication errors |
analog
|
V:3, I:105 | 3534 | web server log analyzer |
awstats
|
V:9, I:14 | 6910 | powerful and featureful web server log analyzer |
sarg
|
V:2, I:3 | 843 | squid analysis report generator |
pflogsumm
|
V:2, I:4 | 111 | Postfix log entry summarizer |
syslog-summary
|
V:0, I:2 | 30 | summarize the contents of a syslog log file |
fwlogwatch
|
V:0, I:0 | 478 | firewall log analyzer |
squidview
|
V:0, I:1 | 189 | monitor and analyze squid access.log files |
swatch
|
V:0, I:0 | 101 | log file viewer with regexp matching, highlighting, and hooks |
crm114
|
V:0, I:0 | 1119 | Controllable Regex Mutilator and Spam Filter (CRM114) |
icmpinfo
|
V:0, I:0 | 44 | interpret ICMP messages |
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Catatan |
---|---|
CRM114 provides language infrastructure to write fuzzy filters with the TRE regex library. Its popular use is spam mail filter but it can be used as log analyzer. |
Although pager tools such as more
(1) and
less
(1) (see Bagian 1.4.5, “The pager”) and custom
tools for highlighting and formatting (see Bagian 11.1.8, “Highlighting and formatting plain text data”) can display text
data nicely, general purpose editors (see Bagian 1.4.6, “The text editor”) are most versatile and customizable.
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Tip |
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For |
The default display format of time and date by the "ls
-l
" command depends on the locale (see Bagian 1.2.6, “Timestamps” for
value). The "$LANG
" variable is referred first and it
can be overridden by the "$LC_TIME
" or
"$LC_ALL
" exported environment variables.
The actual default display format for each locale depends on the version of
the standard C library (the libc6
package) used. I.e.,
different releases of Debian had different defaults. For iso-formats, see
ISO 8601.
If you really wish to customize this display format of time and date beyond
the locale, you should set the time style value by the
"--time-style
" argument or by the
"$TIME_STYLE
" value (see ls
(1),
date
(1), "info coreutils 'ls
invocation'
").
Tabel 9.5. Display examples of time and date for the "ls -l
" command
with the time style value
time style value | locale | display of time and date |
---|---|---|
iso |
any | 01-19 00:15 |
long-iso |
any | 2009-01-19 00:15 |
full-iso |
any | 2009-01-19 00:15:16.000000000 +0900 |
locale |
C |
Jan 19 00:15 |
locale |
en_US.UTF-8 |
Jan 19 00:15 |
locale |
es_ES.UTF-8 |
ene 19 00:15 |
+%d.%m.%y %H:%M |
any | 19.01.09 00:15 |
+%d.%b.%y %H:%M |
C atau en_US.UTF-8 |
19.Jan.09 00:15 |
+%d.%b.%y %H:%M |
es_ES.UTF-8 |
19.ene.09 00:15 |
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Tip |
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You can eliminate typing long option on commandline using command alias (see Bagian 1.5.9, “Command alias”): alias ls='ls --time-style=+%d.%m.%y %H:%M' |
Shell echo to most modern terminals can be colorized using ANSI escape code (see
"/usr/share/doc/xterm/ctlseqs.txt.gz
").
Misalnya, coba yang berikut ini
$ RED=$(printf "\x1b[31m") $ NORMAL=$(printf "\x1b[0m") $ REVERSE=$(printf "\x1b[7m") $ echo "${RED}RED-TEXT${NORMAL} ${REVERSE}REVERSE-TEXT${NORMAL}"
Colorized commands are handy for inspecting their output in the interactive
environment. I include the following in my "~/.bashrc
".
if [ "$TERM" != "dumb" ]; then eval "`dircolors -b`" alias ls='ls --color=always' alias ll='ls --color=always -l' alias la='ls --color=always -A' alias less='less -R' alias ls='ls --color=always' alias grep='grep --color=always' alias egrep='egrep --color=always' alias fgrep='fgrep --color=always' alias zgrep='zgrep --color=always' else alias ll='ls -l' alias la='ls -A' fi
The use of alias limits color effects to the interactive command usage. It
has advantage over exporting environment variable "export
GREP_OPTIONS='--color=auto'
" since color can be seen under pager
programs such as less
(1). If you wish to suppress color
when piping to other programs, use "--color=auto
" instead
in the above example for "~/.bashrc
".
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Tip |
---|---|
You can turn off these colorizing aliases in the interactive environment by
invoking shell with " |
You can record the editor activities for complex repeats.
For Vim, as follows.
"qa
": start recording typed characters into named
register "a
".
… editor activities
"q
": end recording typed characters.
"@a
": execute the contents of register
"a
".
For Emacs, as follows.
"C-x (
": start defining a keyboard macro.
… editor activities
"C-x )
": end defining a keyboard macro.
"C-x e
": execute a keyboard macro.
There are few ways to record the graphic image of an X application,
including an xterm
display.
Tabel 9.6. List of graphic image manipulation tools
paket | popcon | ukuran | layar | command |
---|---|---|---|---|
gnome-screenshot
|
V:27, I:264 | 1173 | Wayland | screenshot application for GNOME |
flameshot
|
V:5, I:11 | 1510 | Wayland | screenshot application on steroid |
gimp
|
V:58, I:315 | 19706 | Wayland + X | screenshot in GUI menu |
x11-apps
|
V:27, I:454 | 2437 | X | xwd (1) |
imagemagick
|
I:373 | 220 | X | import (1) |
scrot
|
V:7, I:76 | 123 | X | scrot (1) |
There are specialized tools to record changes in configuration files with help of DVCS and to make system snapshots on Btrfs.
You may also think about local script Bagian 10.2.2, “Personal backup” approach.
Program activities can be monitored and controlled using specialized tools.
Tabel 9.8. List of tools for monitoring and controlling program activities
paket | popcon | ukuran | deskripsi |
---|---|---|---|
coreutils
|
V:901, I:999 | 17478 | nice (1): run a program with modified scheduling priority |
bsdutils
|
V:708, I:999 | 394 | renice (1): modify the scheduling priority of a running
process |
procps
|
V:742, I:999 | 1648 | "/proc " filesystem utilities: ps (1),
top (1), kill (1),
watch (1), … |
psmisc
|
V:433, I:831 | 793 | "/proc " filesystem utilities:
killall (1), fuser (1),
peekfd (1), pstree (1) |
time
|
V:13, I:249 | 129 | time (1): run a program to report system resource usages
with respect to time |
sysstat
|
V:168, I:190 | 1923 | sar (1), iostat (1),
mpstat (1), …: system performance tools for Linux |
isag
|
V:0, I:4 | 117 | Interactive System Activity Grapher for sysstat |
lsof
|
V:393, I:944 | 451 | lsof (8): list files opened by a running process using
"-p " option |
strace
|
V:16, I:151 | 2367 | strace (1): trace system calls and signals |
ltrace
|
V:1, I:22 | 363 | ltrace (1): trace library calls |
xtrace
|
V:0, I:0 | 353 | xtrace (1): trace communication between X11 client and
server |
powertop
|
V:8, I:204 | 662 | powertop (1): information about system power use |
cron
|
V:800, I:997 | 263 | run processes according to a schedule in background from
cron (8) daemon |
anacron
|
V:399, I:463 | 104 | cron-like command scheduler for systems that don't run 24 hours a day |
at
|
V:154, I:278 | 161 | at (1) or batch (1): run a job at a
specified time or below certain load level |
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Tip |
---|---|
The |
Display time used by the process invoked by the command.
# time some_command >/dev/null real 0m0.035s # time on wall clock (elapsed real time) user 0m0.000s # time in user mode sys 0m0.020s # time in kernel mode
A nice value is used to control the scheduling priority for the process.
Tabel 9.9. List of nice values for the scheduling priority
nice value | scheduling priority |
---|---|
19 | lowest priority process (nice) |
0 | very high priority process for user |
-20 | very high priority process for root (not-nice) |
# nice -19 top # very nice # nice --20 wodim -v -eject speed=2 dev=0,0 disk.img # very fast
Sometimes an extreme nice value does more harm than good to the system. Use this command carefully.
The ps
(1) command on a Debian system support both BSD and
SystemV features and helps to identify the process activity statically.
Tabel 9.10. List of ps command styles
style | typical command | fitur |
---|---|---|
BSD | ps aux |
display %CPU %MEM |
System V | ps -efH |
display PPID |
For the zombie (defunct) children process, you can kill them by the parent
process ID identified in the "PPID
" field.
The pstree
(1) command display a tree of processes.
top
(1) on the Debian system has rich features and helps
to identify what process is acting funny dynamically.
It is an interactive full screen program. You can get its usage help press by pressing the "h"-key and terminate it by pressing the "q"-key.
You can list all files opened by a process with a process ID (PID), e.g. 1, by the following.
$ sudo lsof -p 1
PID=1 is usually the init
program.
You can trace program activity with strace
(1),
ltrace
(1), or xtrace
(1) for system
calls and signals, library calls, or communication between X11 client and
server.
You can trace system calls of the ls
command as the
following.
$ sudo strace ls
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Tip |
---|---|
Use strace-graph script found in /usr/share/doc/strace/examples/ to make a nice tree view |
You can also identify processes using files by fuser
(1),
e.g. for "/var/log/mail.log
" by the following.
$ sudo fuser -v /var/log/mail.log USER PID ACCESS COMMAND /var/log/mail.log: root 2946 F.... rsyslogd
You see that file "/var/log/mail.log
" is open for writing
by the rsyslogd
(8) command.
You can also identify processes using sockets by
fuser
(1), e.g. for "smtp/tcp
" by the
following.
$ sudo fuser -v smtp/tcp USER PID ACCESS COMMAND smtp/tcp: Debian-exim 3379 F.... exim4
Now you know your system runs exim4
(8) to handle TCP connections to SMTP port
(25).
watch
(1) executes a program repeatedly with a constant
interval while showing its output in fullscreen.
$ watch w
This displays who is logged on to the system updated every 2 seconds.
There are several ways to repeat a command looping over files matching some
condition, e.g. matching glob pattern "*.ext
".
Shell for-loop method (see Bagian 12.1.4, “Shell loops”):
for x in *.ext; do if [ -f "$x"]; then command "$x" ; fi; done
find
(1) and xargs
(1) combination:
find . -type f -maxdepth 1 -name '*.ext' -print0 | xargs -0 -n 1 command
find
(1) with "-exec
" option with a
command:
find . -type f -maxdepth 1 -name '*.ext' -exec command '{}' \;
find
(1) with "-exec
" option with a
short shell script:
find . -type f -maxdepth 1 -name '*.ext' -exec sh -c "command '{}' && echo 'successful'" \;
The above examples are written to ensure proper handling of funny file names
such as ones containing spaces. See Bagian 10.1.5, “Idioms for the selection of files” for more advance uses of
find
(1).
For the command-line interface
(CLI), the first program with the matching name found in the
directories specified in the $PATH
environment variable
is executed. See Bagian 1.5.3, “The "$PATH
" variable”.
For the graphical user interface
(GUI) compliant to the freedesktop.org standards, the
*.desktop
files in the
/usr/share/applications/
directory provide necessary
attributes for the GUI menu display of each program. Each package which is
compliant to Freedesktop.org's xdg menu system installs its menu data
provided by "*.desktop" under "/usr/share/applications/". Modern desktop
environments which are compliant to Freedesktop.org standard use these data
to generate their menu using the xdg-utils package. See
"/usr/share/doc/xdg-utils/README".
For example, the chromium.desktop
file defines attributes
for the "Chromium Web Browser" such as "Name" for the program name, "Exec"
for the program execution path and arguments, "Icon" for the icon used,
etc. (see the Desktop Entry
Specification) as follows:
[Desktop Entry] Version=1.0 Name=Chromium Web Browser GenericName=Web Browser Comment=Access the Internet Comment[fr]=Explorer le Web Exec=/usr/bin/chromium %U Terminal=false X-MultipleArgs=false Type=Application Icon=chromium Categories=Network;WebBrowser; MimeType=text/html;text/xml;application/xhtml_xml;x-scheme-handler/http;x-scheme-handler/https; StartupWMClass=Chromium StartupNotify=true
This is an oversimplified description. The *.desktop
files are scanned as follows.
The desktop environment sets $XDG_DATA_HOME
and
$XDG_DATA_DIR
environment variables. For example, under
the GNOME 3:
$XDG_DATA_HOME
is unset. (The default value of
$HOME/.local/share
is used.)
$XDG_DATA_DIRS
is set to
/usr/share/gnome:/usr/local/share/:/usr/share/
.
So the base directories (see XDG Base Directory
Specification) and the applications
directories
are as follows.
$HOME/.local/share/
→
$HOME/.local/share/applications/
/usr/share/gnome/
→
/usr/share/gnome/applications/
/usr/local/share/
→
/usr/local/share/applications/
/usr/share/
→ /usr/share/applications/
The *.desktop
files are scanned in these
applications
directories in this order.
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Tip |
---|---|
A user custom GUI menu entry can be created by adding a
|
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Tip |
---|---|
Similarly, if a |
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Tip |
---|---|
Similarly, if a |
Some programs start another program automatically. Here are check points for customizing this process.
Application configuration menu:
GNOME3 desktop: "Settings" → "System" → "Details" → "Default Applications"
KDE desktop: "K" → "Control Center" → "KDE Components" → "Component Chooser"
Iceweasel browser: "Edit" → "Preferences" → "Applications"
mc
(1): "/etc/mc/mc.ext
"
Environment variables such as "$BROWSER
",
"$EDITOR
", "$VISUAL
", and
"$PAGER
" (see eviron
(7))
The update-alternatives
(1) system for programs such as
"editor
", "view
",
"x-www-browser
", "gnome-www-browser
",
and "www-browser
" (see Bagian 1.4.7, “Setting a default text editor”)
the "~/.mailcap
" and "/etc/mailcap
"
file contents which associate MIME type with
program (see mailcap
(5))
The "~/.mime.types
" and
"/etc/mime.types
" file contents which associate file name
extension with MIME type (see
run-mailcap
(1))
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Tip |
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|
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Tip |
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The |
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Tip |
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In order to run a console application such as |
# cat /usr/local/bin/mutt-term <<EOF #!/bin/sh gnome-terminal -e "mutt \$@" EOF chmod 755 /usr/local/bin/mutt-term
Use kill
(1) to kill (or send a signal to) a process by
the process ID.
Use killall
(1) or pkill
(1) to do the
same by the process command name and other attributes.
Tabel 9.11. List of frequently used signals for kill command
signal value | signal name | aksi | catatan |
---|---|---|---|
0 | --- | no signal is sent (see kill (2)) |
check if process is running |
1 | SIGHUP | terminate the process | disconnected terminal (signal hang up) |
2 | SIGINT | terminate the process | interrupt from keyboard (CTRL-C ) |
3 | SIGQUIT | terminate the process and dump core | quit from keyboard (CTRL-\ ) |
9 | SIGKILL | terminate the process | unblockable kill signal |
15 | SIGTERM | terminate the process | blockable termination signal |
Run the at
(1) command to schedule a one-time job by the
following.
$ echo 'command -args'| at 3:40 monday
Use cron
(8) to schedule tasks regularly. See
crontab
(1) and crontab
(5).
You can schedule to run processes as a normal user,
e.g. foo
by creating a crontab
(5) file
as "/var/spool/cron/crontabs/foo
" with "crontab
-e
" command.
Here is an example of a crontab
(5) file.
# use /bin/sh to run commands, no matter what /etc/passwd says SHELL=/bin/sh # mail any output to paul, no matter whose crontab this is MAILTO=paul # Min Hour DayOfMonth Month DayOfWeek command (Day... are OR'ed) # run at 00:05, every day 5 0 * * * $HOME/bin/daily.job >> $HOME/tmp/out 2>&1 # run at 14:15 on the first of every month -- output mailed to paul 15 14 1 * * $HOME/bin/monthly # run at 22:00 on weekdays(1-5), annoy Joe. % for newline, last % for cc: 0 22 * * 1-5 mail -s "It's 10pm" joe%Joe,%%Where are your kids?%.%% 23 */2 1 2 * echo "run 23 minutes after 0am, 2am, 4am ..., on Feb 1" 5 4 * * sun echo "run at 04:05 every Sunday" # run at 03:40 on the first Monday of each month 40 3 1-7 * * [ "$(date +%a)" == "Mon" ] && command -args
![]() |
Tip |
---|---|
For the system not running continuously, install the
|
![]() |
Tip |
---|---|
For scheduled system maintenance scripts, you can run them periodically from
root account by placing such scripts in
" |
Systemd has low level capability to schedule
programs to run without cron
daemon. For example,
/lib/systemd/system/apt-daily.timer
and
/lib/systemd/system/apt-daily.service
set up daily apt
download activities. See systemd.timer
(5) .
Pressing Alt-SysRq (PrtScr) followed by one keys does the magic of rescuing control of the system.
Tabel 9.12. List of notable SAK command keys
key following Alt-SysRq | description of action |
---|---|
k |
kill all processes on the current virtual console (SAK) |
s |
sync all mounted filesystems to avoid data corruption |
u |
remount all mounted filesystems read-only (umount) |
r |
restore the keyboard from raw mode after X crashes |
See more on Linux kernel user’s and administrator’s guide » Linux Magic System Request Key Hacks
![]() |
Tip |
---|---|
From SSH terminal etc., you can use the Alt-SysRq feature by writing to the
" |
The current (2021) Debian amd64 Linux kernel has
/proc/sys/kernel/sysrq=438=0b110110110
:
2 = 0x2 - enable control of console logging level (ON)
4 = 0x4 - enable control of keyboard (SAK, unraw) (ON)
8 = 0x8 - enable debugging dumps of processes etc. (OFF)
16 = 0x10 - enable sync command (ON)
32 = 0x20 - enable remount read-only (ON)
64 = 0x40 - enable signaling of processes (term, kill, oom-kill) (OFF)
128 = 0x80 - allow reboot/poweroff (ON)
256 = 0x100 - allow nicing of all RT tasks (ON)
You can check who is on the system by the following.
who
(1) shows who is logged on.
w
(1) shows who is logged on and what they are doing.
last
(1) shows listing of last logged in user.
lastb
(1) shows listing of last bad logged in users.
![]() |
Tip |
---|---|
" |
You can send message to everyone who is logged on to the system with
wall
(1) by the following.
$ echo "We are shutting down in 1 hour" | wall
For the PCI-like devices (AGP, PCI-Express,
CardBus, ExpressCard, etc.), lspci
(8)
(probably with "-nn
" option) is a good start for the
hardware identification.
Alternatively, you can identify the hardware by reading contents of
"/proc/bus/pci/devices
" or browsing directory tree under
"/sys/bus/pci
" (see Bagian 1.2.12, “procfs and sysfs”).
Tabel 9.13. List of hardware identification tools
paket | popcon | ukuran | deskripsi |
---|---|---|---|
pciutils
|
V:200, I:991 | 196 | Linux PCI Utilities: lspci (8) |
usbutils
|
V:73, I:858 | 325 | Linux USB utilities: lsusb (8) |
nvme-cli
|
V:2, I:10 | 779 | NVMe utilities for Linux: nvme (1) |
pcmciautils
|
V:11, I:17 | 97 | PCMCIA utilities for Linux: pccardctl (8) |
scsitools
|
V:0, I:3 | 375 | collection of tools for SCSI hardware management:
lsscsi (8) |
procinfo
|
V:0, I:12 | 135 | system information obtained from "/proc ":
lsdev (8) |
lshw
|
V:11, I:96 | 850 | information about hardware configuration: lshw (1) |
discover
|
V:37, I:948 | 90 | hardware identification system: discover (8) |
Although most of the hardware configuration on modern GUI desktop systems such as GNOME and KDE can be managed through accompanying GUI configuration tools, it is a good idea to know some basics methods to configure them.
Tabel 9.14. List of hardware configuration tools
paket | popcon | ukuran | deskripsi |
---|---|---|---|
console-setup
|
V:133, I:960 | 419 | Linux console font and keytable utilities |
x11-xserver-utils
|
V:272, I:516 | 511 | X server utilities: xset (1),
xmodmap (1) |
acpid
|
V:135, I:281 | 176 | daemon to manage events delivered by the Advanced Configuration and Power Interface (ACPI) |
acpi
|
V:15, I:266 | 45 | utility to display information on ACPI devices |
sleepd
|
V:0, I:0 | 86 | daemon to put a laptop to sleep during inactivity |
hdparm
|
V:446, I:717 | 256 | hard disk access optimization (see Bagian 9.6.9, “Optimization of hard disk”) |
smartmontools
|
V:150, I:208 | 2117 | control and monitor storage systems using S.M.A.R.T. |
setserial
|
V:5, I:9 | 117 | collection of tools for serial port management |
memtest86+
|
V:1, I:28 | 2391 | collection of tools for memory hardware management |
scsitools
|
V:0, I:3 | 375 | collection of tools for SCSI hardware management |
setcd
|
V:0, I:1 | 35 | compact disc drive access optimization |
big-cursor
|
I:1 | 27 | larger mouse cursors for X |
Here, ACPI is a newer framework for the power management system than APM.
![]() |
Tip |
---|---|
CPU frequency scaling on modern system is governed by kernel modules such as
|
The following sets system and hardware time to MM/DD hh:mm, CCYY.
# date MMDDhhmmCCYY # hwclock --utc --systohc # hwclock --show
Times are normally displayed in the local time on the Debian system but the hardware and system time usually use UTC(GMT).
If the hardware time is set to UTC, change the setting to
"UTC=yes
" in the "/etc/default/rcS
".
The following reconfigure the timezone used by the Debian system.
# dpkg-reconfigure tzdata
If you wish to update system time via network, consider to use the NTP service with the packages such as
ntp
, ntpdate
, and
chrony
.
![]() |
Tip |
---|---|
Under systemd, use
|
See the following.
The ntp-doc
package
![]() |
Tip |
---|---|
|
There are several components to configure character console and
ncurses
(3) system features.
The "/etc/terminfo/*/*
" file
(terminfo
(5))
The "$TERM
" environment variable
(term
(7))
setterm
(1), stty
(1),
tic
(1), and toe
(1)
If the terminfo
entry for xterm
doesn't work with a non-Debian xterm
, change your
terminal type, "$TERM
", from "xterm
"
to one of the feature-limited versions such as "xterm-r6
"
when you log in to a Debian system remotely. See
"/usr/share/doc/libncurses5/FAQ
" for more.
"dumb
" is the lowest common denominator for
"$TERM
".
Device drivers for sound cards for current Linux are provided by Advanced Linux Sound Architecture (ALSA). ALSA provides emulation mode for previous Open Sound System (OSS) for compatibility.
Application softwares may be configured not only to access sound devices directly but also to access them via some standardized sound server system. Currently, PulseAudio, JACK, and PipeWire are used as sound server system. See Debian wiki page on Sound for the latest situation.
There is usually a common sound engine for each popular desktop environment. Each sound engine used by the application can choose to connect to different sound servers.
![]() |
Tip |
---|---|
Use " |
![]() |
Tip |
---|---|
If you can not get sound, your speaker may be connected to a muted output.
Modern sound system has many outputs. |
Tabel 9.15. List of sound packages
paket | popcon | ukuran | deskripsi |
---|---|---|---|
alsa-utils
|
V:337, I:456 | 2283 | utilities for configuring and using ALSA |
oss-compat
|
V:1, I:27 | 20 | OSS compatibility under ALSA preventing "/dev/dsp not
found " errors |
pipewire
|
V:59, I:78 | 30 | audio and video processing engine multimedia server - metapackage (unify JACK and PulseAudio) |
pipewire-bin
|
V:67, I:76 | 1848 | audio and video processing engine multimedia server - programs (unify JACK and PulseAudio) |
pipewire-audio-client-libraries
|
V:0, I:1 | 380 | audio and video processing engine multimedia server - audio client libraries to replace ALSA, JACK and PulseAudio (experimental) |
pulseaudio
|
V:357, I:453 | 6774 | PulseAudio server (standard) |
libpulse0
|
V:292, I:586 | 971 | PulseAudio client library (standard) |
jackd
|
V:3, I:26 | 9 | JACK Audio Connection Kit. (JACK) server (low latency) |
libjack0
|
V:1, I:12 | 338 | JACK Audio Connection Kit. (JACK) library (low latency) |
libgstreamer1.0-0
|
V:374, I:567 | 5283 | GStreamer: GNOME sound engine |
libphonon4
|
I:101 | 680 | Phonon: KDE sound engine |
For disabling the screen saver, use following commands.
Tabel 9.16. List of commands for disabling the screen saver
environment | command |
---|---|
The Linux console | setterm -powersave off |
The X Window (turning off screensaver) | xset s off |
The X Window (disabling dpms) | xset -dpms |
The X Window (GUI configuration of screen saver) | xscreensaver-command -prefs |
One can always unplug the PC speaker to disable beep sounds. Removing
pcspkr
kernel module does this for you.
The following prevents the readline
(3) program used by
bash
(1) to beep when encountering an alert character
(ASCII=7).
$ echo "set bell-style none">> ~/.inputrc
There are 2 resources available for you to get the memory usage situation.
The kernel boot message in the "/var/log/dmesg
" contains
the total exact size of available memory.
free
(1) and top
(1) display information
on memory resources on the running system.
Here is an example.
# grep '\] Memory' /var/log/dmesg [ 0.004000] Memory: 990528k/1016784k available (1975k kernel code, 25868k reserved, 931k data, 296k init) $ free -k total used free shared buffers cached Mem: 997184 976928 20256 0 129592 171932 -/+ buffers/cache: 675404 321780 Swap: 4545576 4 4545572
You may be wondering "dmesg tells me a free of 990 MB, and free -k says 320 MB is free. More than 600 MB missing …".
Do not worry about the large size of "used
" and the small
size of "free
" in the "Mem:
" line, but
read the one under them (675404 and 321780 in the example above) and relax.
For my MacBook with 1GB=1048576k DRAM (video system steals some of this), I see the following.
Tabel 9.17. List of memory sizes reported
report | ukuran |
---|---|
Total size in dmesg | 1016784k = 1GB - 31792k |
Free in dmesg | 990528k |
Total under shell | 997184k |
Free under shell | 20256k (but effectively 321780k) |
Poor system maintenance may expose your system to external exploitation.
For system security and integrity check, you should start with the following.
The debsums
package, see debsums
(1)
and Bagian 2.5.2, “Top level "Release" file and authenticity”.
The chkrootkit
package, see
chkrootkit
(1).
The clamav
package family, see
clamscan
(1) and freshclam
(1).
Tabel 9.18. List of tools for system security and integrity check
paket | popcon | ukuran | deskripsi |
---|---|---|---|
logcheck
|
V:8, I:10 | 102 | daemon to mail anomalies in the system logfiles to the administrator |
debsums
|
V:5, I:44 | 108 | utility to verify installed package files against MD5 checksums |
chkrootkit
|
V:5, I:24 | 971 | rootkit detector |
clamav
|
V:12, I:57 | 775 | anti-virus utility for Unix - command-line interface |
tiger
|
V:2, I:3 | 7822 | report system security vulnerabilities |
tripwire
|
V:2, I:3 | 11618 | file and directory integrity checker |
john
|
V:2, I:12 | 460 | active password cracking tool |
aide
|
V:1, I:2 | 2049 | Advanced Intrusion Detection Environment - static binary |
integrit
|
V:0, I:0 | 329 | file integrity verification program |
crack
|
V:0, I:1 | 152 | password guessing program |
Here is a simple script to check for typical world writable incorrect file permissions.
# find / -perm 777 -a \! -type s -a \! -type l -a \! \( -type d -a -perm 1777 \)
![]() |
Perhatian |
---|---|
Since the |
Booting your system with Linux live CDs or debian-installer CDs in rescue mode makes it easy for you to reconfigure data storage on your boot device.
You may need to umount
(8) some devices manually from the
command line before operating on them if they are automatically mounted by
the GUI desktop system.
The disk space usage can be evaluated by programs provided by the
mount
, coreutils
, and
xdu
packages:
mount
(8) reports all mounted filesystems (= disks).
df
(1) reports the disk space usage for the file system.
du
(1) reports the disk space usage for the directory
tree.
![]() |
Tip |
---|---|
You can feed the output of |
For disk partition configuration,
although fdisk
(8) has been considered standard,
parted
(8) deserves some attention. "Disk partitioning
data", "partition table", "partition map", and "disk label" are all
synonyms.
Older PCs use the classic Master Boot Record (MBR) scheme to hold disk partitioning data in the first sector, i.e., LBA sector 0 (512 bytes).
Recent PCs with Unified Extensible Firmware Interface (UEFI), including Intel-based Macs, use GUID Partition Table (GPT) scheme to hold disk partitioning data not in the first sector.
Although fdisk
(8) has been standard for the disk
partitioning tool, parted
(8) is replacing it.
Tabel 9.19. List of disk partition management packages
paket | popcon | ukuran | deskripsi |
---|---|---|---|
util-linux
|
V:899, I:999 | 4599 | miscellaneous system utilities including fdisk (8) and
cfdisk (8) |
parted
|
V:367, I:548 | 307 | GNU Parted disk partition resizing program |
gparted
|
V:16, I:127 | 2063 | GNOME partition editor based on libparted |
gdisk
|
V:298, I:501 | 880 | partition editor for the GPT/MBR hybrid disk |
kpartx
|
V:19, I:30 | 87 | program to create device mappings for partitions |
![]() |
Perhatian |
---|---|
Although |
![]() |
Catatan |
---|---|
In order to switch between GPT and MBR, you need to erase first few blocks of disk contents
directly (see Bagian 9.8.6, “Clearing file contents”) and use
" |
Although reconfiguration of your partition or activation order of removable storage media may yield different names for partitions, you can access them consistently. This is also helpful if you have multiple disks and your BIOS/UEFI doesn't give them consistent device names.
mount
(8) with "-U
" option can mount a
block device using UUID, instead of using its
file name such as "/dev/sda3
".
"/etc/fstab
" (see fstab
(5)) can use
UUID.
Boot loaders (Bagian 3.1.2, “Stage 2: the boot loader”) may use UUID too.
![]() |
Tip |
---|---|
You can probe UUID of a block special device
with You can also probe it and other information with " |
LVM2 is a logical volume manager for the Linux kernel. With LVM2, disk partitions can be created on logical volumes instead of the physical harddisks.
LVM requires the following.
device-mapper support in the Linux kernel (default for Debian kernels)
the userspace device-mapper support library
(libdevmapper*
package)
the userspace LVM2 tools (lvm2
package)
Please start learning LVM2 from the following manpages.
lvm
(8): Basics of LVM2 mechanism (list of all LVM2
commands)
lvm.conf
(5): Configuration file for LVM2
lvs
(8): Report information about logical volumes
vgs
(8): Report information about volume groups
pvs
(8): Report information about physical volumes
For ext4 filesystem, the
e2fsprogs
package provides the following.
The mkfs
(8) and fsck
(8) commands are
provided by the e2fsprogs
package as front-ends to
various filesystem dependent programs (mkfs.fstype
and
fsck.fstype
). For ext4
filesystem, they are mkfs.ext4
(8) and
fsck.ext4
(8) (they are symlinked to
mke2fs
(8) and e2fsck
(8)).
Similar commands are available for each filesystem supported by Linux.
Tabel 9.20. List of filesystem management packages
paket | popcon | ukuran | deskripsi |
---|---|---|---|
e2fsprogs
|
V:616, I:999 | 1511 | utilities for the ext2/ext3/ext4 filesystems |
btrfs-progs
|
V:44, I:68 | 3959 | utilities for the Btrfs filesystem |
reiserfsprogs
|
V:15, I:29 | 1132 | utilities for the Reiserfs filesystem |
zfsutils-linux
|
V:19, I:23 | 1497 | utilities for the OpenZFS filesystem |
dosfstools
|
V:132, I:508 | 315 | utilities for the FAT filesystem. (Microsoft: MS-DOS, Windows) |
exfatprogs
|
V:0, I:1 | 161 | utilities for the exFAT filesystem maintained by Samsung. |
exfat-fuse
|
V:25, I:429 | 71 | read/write exFAT filesystem (Microsoft) driver for FUSE. |
exfat-utils
|
V:19, I:430 | 231 | utilities for the exFAT filesystem maintained by the exfat-fuse author. |
xfsprogs
|
V:22, I:101 | 3281 | utilities for the XFS filesystem. (SGI: IRIX) |
ntfs-3g
|
V:227, I:494 | 1483 | read/write NTFS filesystem (Microsoft: Windows NT, …) driver for FUSE. |
jfsutils
|
V:1, I:12 | 1577 | utilities for the JFS filesystem. (IBM: AIX, OS/2) |
reiser4progs
|
V:0, I:4 | 1373 | utilities for the Reiser4 filesystem |
hfsprogs
|
V:0, I:7 | 389 | utilities for HFS and HFS Plus filesystem. (Apple: Mac OS) |
zerofree
|
V:3, I:100 | 25 | program to zero free blocks from ext2/3/4 filesystems |
![]() |
Tip |
---|---|
Ext4 filesystem is the default filesystem for the Linux system and strongly recommended to use it unless you have some specific reasons not to. Btrfs status can be found at Debian wiki on btrfs and kernel.org wiki on btrfs. It is expected to be the next default filesystem after the ext4 filesystem. Some tools allow access to filesystem without Linux kernel support (see Bagian 9.8.2, “Manipulating files without mounting disk”). |
The mkfs
(8) command creates the filesystem on a Linux
system. The fsck
(8) command provides the filesystem
integrity check and repair on a Linux system.
Debian now defaults to no periodic fsck
after filesystem
creation.
![]() |
Perhatian |
---|---|
It is generally not safe to run |
![]() |
Tip |
---|---|
You can run the Check files in " |
The basic static filesystem configuration is given by
"/etc/fstab
". For example,
«file system» «mount point» «type» «options» «dump» «pass» proc /proc proc defaults 0 0 UUID=709cbe4c-80c1-56db-8ab1-dbce3146d2f7 / ext4 errors=remount-ro 0 1 UUID=817bae6b-45d2-5aca-4d2a-1267ab46ac23 none swap sw 0 0 /dev/scd0 /media/cdrom0 udf,iso9660 user,noauto 0 0
![]() |
Tip |
---|---|
UUID (see Bagian 9.6.3, “Accessing partition using UUID”) may be used to identify a block
device instead of normal block device names such as
" |
Since Linux 2.6.30, the kernel defaults to the behavior provided by
"relatime
" option.
Lihat fstab
(5) dan mount
(8).
Characteristics of a filesystem can be optimized via its superblock using
the tune2fs
(8) command.
Execution of "sudo tune2fs -l /dev/hda1
" displays the
contents of the filesystem superblock on "/dev/hda1
".
Execution of "sudo tune2fs -c 50 /dev/hda1
" changes
frequency of filesystem checks (fsck
execution during
boot-up) to every 50 boots on "/dev/hda1
".
Execution of "sudo tune2fs -j /dev/hda1
" adds journaling
capability to the filesystem, i.e. filesystem conversion from ext2 to ext3 on
"/dev/hda1
". (Do this on the unmounted filesystem.)
Execution of "sudo tune2fs -O extents,uninit_bg,dir_index /dev/hda1
&& fsck -pf /dev/hda1
" converts it from ext3 to ext4 on
"/dev/hda1
". (Do this on the unmounted filesystem.)
![]() |
Awas |
---|---|
Please check your hardware and read manpage of |
You can test disk access speed of a hard disk,
e.g. "/dev/hda
", by "hdparm -tT
/dev/hda
". For some hard disk connected with (E)IDE, you can speed
it up with "hdparm -q -c3 -d1 -u1 -m16 /dev/hda
" by
enabling the "(E)IDE 32-bit I/O support", enabling the "using_dma flag",
setting "interrupt-unmask flag", and setting the "multiple 16 sector I/O"
(dangerous!).
You can test write cache feature of a hard disk,
e.g. "/dev/sda
", by "hdparm -W
/dev/sda
". You can disable its write cache feature with
"hdparm -W 0 /dev/sda
".
You may be able to read badly pressed CDROMs on modern high speed CD-ROM
drive by slowing it down with "setcd -x 2
".
Solid state drive (SSD) is auto detected now.
Reduce unnecessary disk accesses to prevent disk wear out by mounting
"tmpfs
" on volatile data path in
/etc/fstab
.
You can monitor and log your hard disk which is compliant to SMART with the smartd
(8) daemon.
Install the smartmontools
package.
Identify your hard disk drives by listing them with
df
(1).
Let's assume a hard disk drive to be monitored as
"/dev/hda
".
Check the output of "smartctl -a /dev/hda
" to see if
SMART feature is actually enabled.
If not, enable it by "smartctl -s on -a /dev/hda
".
Enable smartd
(8) daemon to run by the following.
uncomment "start_smartd=yes
" in the
"/etc/default/smartmontools
" file.
restart the smartd
(8) daemon by "sudo systemctl
restart smartmontools
".
![]() |
Tip |
---|---|
The |
Applications create temporary files normally under the temporary storage
directory "/tmp
". If "/tmp
" does not
provide enough space, you can specify such temporary storage directory via
the $TMPDIR
variable for well-behaving programs.
For partitions created on Logical Volume Manager (LVM) (Linux feature) at install time, they can be resized easily by concatenating extents onto them or truncating extents from them over multiple storage devices without major system reconfiguration.
If you have an empty partition (e.g., "/dev/sdx
"), you
can format it with mkfs.ext4
(1) and
mount
(8) it to a directory where you need more
space. (You need to copy original data contents.)
$ sudo mv work-dir old-dir $ sudo mkfs.ext4 /dev/sdx $ sudo mount -t ext4 /dev/sdx work-dir $ sudo cp -a old-dir/* work-dir $ sudo rm -rf old-dir
![]() |
Tip |
---|---|
You may alternatively mount an empty disk image file (see Bagian 9.7.5, “Making the empty disk image file”) as a loop device (see Bagian 9.7.3, “Mounting the disk image file”). The actual disk usage grows with the actual data stored. |
If you have an empty directory (e.g., "/path/to/emp-dir
")
on another partition with usable space, you can mount(8) it with
"--bind
" option to a directory (e.g.,
"work-dir
") where you need more space.
$ sudo mount --bind /path/to/emp-dir work-dir
If you have usable space in another partition (e.g.,
"/path/to/empty
" and "/path/to/work
"),
you can create a directory in it and stack that on to an old directory
(e.g., "/path/to/old
") where you need space using the
OverlayFS for Linux kernel 3.18 or newer
(Debian Stretch 9.0 or newer).
$ sudo mount -t overlay overlay \ -olowerdir=/path/to/old-dir,upperdir=/path/to/empty,workdir=/path/to/work
Here, "/path/to/empty
" and
"/path/to/work
" should be on the RW-enabled partition to
write on "/path/to/old
".
![]() |
Perhatian |
---|---|
This is a deprecated method. Some software may not function well with "symlink to a directory". Instead, use the "mounting" approaches described in the above. |
If you have an empty directory (e.g., "/path/to/emp-dir
")
in another partition with usable space, you can create a symlink to the
directory with ln
(8).
$ sudo mv work-dir old-dir $ sudo mkdir -p /path/to/emp-dir $ sudo ln -sf /path/to/emp-dir work-dir $ sudo cp -a old-dir/* work-dir $ sudo rm -rf old-dir
![]() |
Awas |
---|---|
Do not use "symlink to a directory" for directories managed by the system
such as " |
Here, we discuss manipulations of the disk image.
The disk image file, "disk.img
", of an unmounted device,
e.g., the second SCSI or serial ATA drive "/dev/sdb
", can
be made using cp
(1) or dd
(1) by the
following.
# cp /dev/sdb disk.img # dd if=/dev/sdb of=disk.img
The disk image of the traditional PC's master boot record (MBR) (see Bagian 9.6.2, “Disk partition configuration”) which reside on the first sector
on the primary IDE disk can be made by using dd
(1) by the
following.
# dd if=/dev/hda of=mbr.img bs=512 count=1 # dd if=/dev/hda of=mbr-nopart.img bs=446 count=1 # dd if=/dev/hda of=mbr-part.img skip=446 bs=1 count=66
"mbr.img
": The MBR with the partition table
"mbr-nopart.img
": The MBR without the partition table
"mbr-part.img
": The partition table of the MBR only
If you have an SCSI or serial ATA device as the boot disk, substitute
"/dev/hda
" with "/dev/sda
".
If you are making an image of a disk partition of the original disk,
substitute "/dev/hda
" with "/dev/hda1
"
etc.
The disk image file, "disk.img
" can be written to an
unmounted device, e.g., the second SCSI drive "/dev/sdb
"
with matching size, by the following.
# dd if=disk.img of=/dev/sdb
Similarly, the disk partition image file, "partition.img
"
can be written to an unmounted partition, e.g., the first partition of the
second SCSI drive "/dev/sdb1
" with matching size, by the
following.
# dd if=partition.img of=/dev/sdb1
The disk image "partition.img
" containing a single
partition image can be mounted and unmounted by using the loop device as follows.
# losetup -v -f partition.img Loop device is /dev/loop0 # mkdir -p /mnt/loop0 # mount -t auto /dev/loop0 /mnt/loop0 ...hack...hack...hack # umount /dev/loop0 # losetup -d /dev/loop0
This can be simplified as follows.
# mkdir -p /mnt/loop0 # mount -t auto -o loop partition.img /mnt/loop0 ...hack...hack...hack # umount partition.img
Each partition of the disk image "disk.img
" containing
multiple partitions can be mounted by using the loop device. Since the loop device does not
manage partitions by default, we need to reset it as follows.
# modinfo -p loop # verify kernel capability max_part:Maximum number of partitions per loop device max_loop:Maximum number of loop devices # losetup -a # verify nothing using the loop device # rmmod loop # modprobe loop max_part=16
Now, the loop device can manage up to 16 partitions.
# losetup -v -f disk.img Loop device is /dev/loop0 # fdisk -l /dev/loop0 Disk /dev/loop0: 5368 MB, 5368709120 bytes 255 heads, 63 sectors/track, 652 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Disk identifier: 0x452b6464 Device Boot Start End Blocks Id System /dev/loop0p1 1 600 4819468+ 83 Linux /dev/loop0p2 601 652 417690 83 Linux # mkdir -p /mnt/loop0p1 # mount -t ext4 /dev/loop0p1 /mnt/loop0p1 # mkdir -p /mnt/loop0p2 # mount -t ext4 /dev/loop0p2 /mnt/loop0p2 ...hack...hack...hack # umount /dev/loop0p1 # umount /dev/loop0p2 # losetup -d /dev/loop0
Alternatively, similar effects can be done by using the device mapper devices created by
kpartx
(8) from the kpartx
package as
follows.
# kpartx -a -v disk.img ... # mkdir -p /mnt/loop0p2 # mount -t ext4 /dev/mapper/loop0p2 /mnt/loop0p2 ... ...hack...hack...hack # umount /dev/mapper/loop0p2 ... # kpartx -d /mnt/loop0
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Catatan |
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You can mount a single partition of such disk image with loop device using offset to skip MBR etc., too. But this is more error prone. |
A disk image file, "disk.img
" can be cleaned of all
removed files into clean sparse image "new.img
" by the
following.
# mkdir old; mkdir new # mount -t auto -o loop disk.img old # dd bs=1 count=0 if=/dev/zero of=new.img seek=5G # mount -t auto -o loop new.img new # cd old # cp -a --sparse=always ./ ../new/ # cd .. # umount new.img # umount disk.img
If "disk.img
" is in ext2, ext3 or ext4, you can also use
zerofree
(8) from the zerofree
package
as follows.
# losetup -f -v disk.img Loop device is /dev/loop3 # zerofree /dev/loop3 # cp --sparse=always disk.img new.img
The empty disk image "disk.img
" which can grow up to 5GiB
can be made using dd
(1) as follows.
$ dd bs=1 count=0 if=/dev/zero of=disk.img seek=5G
You can create an ext4 filesystem on this disk image
"disk.img
" using the loop
device as follows.
# losetup -f -v disk.img Loop device is /dev/loop1 # mkfs.ext4 /dev/loop1 ...hack...hack...hack # losetup -d /dev/loop1 $ du --apparent-size -h disk.img 5.0G disk.img $ du -h disk.img 83M disk.img
For "disk.img
", its file size is 5.0 GiB and its actual
disk usage is mere 83MiB. This discrepancy is possible since ext4 can hold sparse
file.
![]() |
Tip |
---|---|
The actual disk usage of sparse file grows with data which are written to it. |
Using similar operation on devices created by the loop device or the device mapper devices as Bagian 9.7.3, “Mounting the disk image file”, you can partition this disk image
"disk.img
" using parted
(8) or
fdisk
(8), and can create filesystem on it using
mkfs.ext4
(8), mkswap
(8), etc.
The ISO9660 image file,
"cd.iso
", from the source directory tree at
"source_directory
" can be made using
genisoimage
(1) provided by cdrkit by the following.
# genisoimage -r -J -T -V volume_id -o cd.iso source_directory
Similarly, the bootable ISO9660 image file, "cdboot.iso
",
can be made from debian-installer
like directory tree at
"source_directory
" by the following.
# genisoimage -r -o cdboot.iso -V volume_id \ -b isolinux/isolinux.bin -c isolinux/boot.cat \ -no-emul-boot -boot-load-size 4 -boot-info-table source_directory
Here Isolinux boot loader (see Bagian 3.1.2, “Stage 2: the boot loader”) is used for booting.
You can calculate the md5sum value and make the ISO9660 image directly from the CD-ROM device as follows.
$ isoinfo -d -i /dev/cdrom CD-ROM is in ISO 9660 format ... Logical block size is: 2048 Volume size is: 23150592 ... # dd if=/dev/cdrom bs=2048 count=23150592 conv=notrunc,noerror | md5sum # dd if=/dev/cdrom bs=2048 count=23150592 conv=notrunc,noerror > cd.iso
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Awas |
---|---|
You must carefully avoid ISO9660 filesystem read ahead bug of Linux as above to get the right result. |
![]() |
Tip |
---|---|
DVD is only a large CD to |
You can find a usable device by the following.
# wodim --devices
Then the blank CD-R is inserted to the CD drive, and the ISO9660 image file,
"cd.iso
" is written to this device, e.g.,
"/dev/hda
", using wodim
(1) by the
following.
# wodim -v -eject dev=/dev/hda cd.iso
If CD-RW is used instead of CD-R, do this instead by the following.
# wodim -v -eject blank=fast dev=/dev/hda cd.iso
![]() |
Tip |
---|---|
If your desktop system mounts CDs automatically, unmount it by
" |
If "cd.iso
" contains an ISO9660 image, then the following
manually mounts it to "/cdrom
".
# mount -t iso9660 -o ro,loop cd.iso /cdrom
![]() |
Tip |
---|---|
Modern desktop system may mount removable media such as ISO9660 formatted CD automatically (see Bagian 10.1.7, “Removable storage device”). |
Here, we discuss direct manipulations of the binary data on storage media.
The most basic viewing method of binary data is to use "od -t
x1
" command.
Tabel 9.21. List of packages which view and edit binary data
paket | popcon | ukuran | deskripsi |
---|---|---|---|
coreutils
|
V:901, I:999 | 17478 | basic package which has od (1) to dump files (HEX, ASCII,
OCTAL, …) |
bsdmainutils
|
V:53, I:953 | 27 | utility package which has hd (1) to dump files (HEX,
ASCII, OCTAL, …) |
hexedit
|
V:1, I:12 | 73 | binary editor and viewer (HEX, ASCII) |
bless
|
V:0, I:4 | 1028 | full featured hexadecimal editor (GNOME) |
okteta
|
V:1, I:14 | 1504 | full featured hexadecimal editor (KDE4) |
ncurses-hexedit
|
V:0, I:2 | 132 | binary editor and viewer (HEX, ASCII, EBCDIC) |
beav
|
V:0, I:0 | 133 | binary editor and viewer (HEX, ASCII, EBCDIC, OCTAL, …) |
![]() |
Tip |
---|---|
HEX is used as an acronym for hexadecimal format with radix 16. OCTAL is for octal format with radix 8. ASCII is for American Standard Code for Information Interchange, i.e., normal English text code. EBCDIC is for Extended Binary Coded Decimal Interchange Code used on IBM mainframe operating systems. |
There are tools to read and write files without mounting disk.
Software RAID systems offered by the Linux kernel provide data redundancy in the kernel filesystem level to achieve high levels of storage reliability.
There are tools to add data redundancy to files in application program level to achieve high levels of storage reliability, too.
Tabel 9.23. List of tools to add data redundancy to files
paket | popcon | ukuran | deskripsi |
---|---|---|---|
par2
|
V:4, I:26 | 271 | Parity Archive Volume Set, for checking and repair of files |
dvdisaster
|
V:0, I:2 | 1741 | data loss/scratch/aging protection for CD/DVD media |
dvbackup
|
V:0, I:0 | 413 | backup tool using MiniDV camcorders (providing rsbep (1)) |
vdmfec
|
V:0, I:0 | 97 | recover lost blocks using Forward Error Correction |
There are tools for data file recovery and forensic analysis.
Tabel 9.24. List of packages for data file recovery and forensic analysis
paket | popcon | ukuran | deskripsi |
---|---|---|---|
testdisk
|
V:3, I:37 | 1426 | utilities for partition scan and disk recovery |
magicrescue
|
V:0, I:3 | 259 | utility to recover files by looking for magic bytes |
scalpel
|
V:0, I:4 | 87 | frugal, high performance file carver |
myrescue
|
V:0, I:3 | 83 | rescue data from damaged harddisks |
extundelete
|
V:0, I:11 | 147 | utility to undelete files on the ext3/4 filesystem |
ext4magic
|
V:0, I:5 | 233 | utility to undelete files on the ext3/4 filesystem |
ext3grep
|
V:0, I:3 | 293 | tool to help recover deleted files on the ext3 filesystem |
scrounge-ntfs
|
V:0, I:3 | 50 | data recovery program for NTFS filesystems |
gzrt
|
V:0, I:0 | 33 | gzip recovery toolkit |
sleuthkit
|
V:2, I:25 | 1511 | tools for forensics analysis. (Sleuthkit) |
autopsy
|
V:0, I:1 | 1027 | graphical interface to SleuthKit |
foremost
|
V:0, I:7 | 100 | forensics application to recover data |
guymager
|
V:0, I:1 | 1035 | forensic imaging tool based on Qt |
dcfldd
|
V:0, I:5 | 106 | enhanced version of dd for forensics and security |
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Tip |
---|---|
You can undelete files on the ext2 filesystem using
|
When a data is too big to backup as a single file, you can backup its content after splitting it into, e.g. 2000MiB chunks and merge those chunks back into the original file later.
$ split -b 2000m large_file $ cat x* >large_file
![]() |
Perhatian |
---|---|
Please make sure you do not have any files starting with
" |
In order to clear the contents of a file such as a log file, do not use
rm
(1) to delete the file and then create a new empty
file, because the file may still be accessed in the interval between
commands. The following is the safe way to clear the contents of the file.
$ :>file_to_be_cleared
The following commands create dummy or empty files.
$ dd if=/dev/zero of=5kb.file bs=1k count=5 $ dd if=/dev/urandom of=7mb.file bs=1M count=7 $ touch zero.file $ : > alwayszero.file
You should find following files.
"5kb.file
" is 5KB of zeros.
"7mb.file
" is 7MB of random data.
"zero.file
" may be a 0 byte file. If it existed, its
mtime
is updated while its content and its length are
kept.
"alwayszero.file
" is always a 0 byte file. If it
existed, its mtime
is updated and its content is reset.
There are several ways to completely erase data from an entire hard disk
like device, e.g., USB memory stick at "/dev/sda
".
![]() |
Perhatian |
---|---|
Check your USB memory stick location with |
Erase all the disk content by resetting data to 0 with the following.
# dd if=/dev/zero of=/dev/sda
Erase everything by overwriting with random data as follows.
# dd if=/dev/urandom of=/dev/sda
Erase everything by overwriting with random data very efficiently as follows.
# shred -v -n 1 /dev/sda
Since dd
(1) is available from the shell of many bootable
Linux CDs such as Debian installer CD, you can erase your installed system
completely by running an erase command from such media on the system hard
disk, e.g., "/dev/hda
", "/dev/sda
",
etc.
Unused area on an hard disk (or USB memory stick),
e.g. "/dev/sdb1
" may still contain erased data themselves
since they are only unlinked from the filesystem. These can be cleaned by
overwriting them.
# mount -t auto /dev/sdb1 /mnt/foo # cd /mnt/foo # dd if=/dev/zero of=junk dd: writing to `junk': No space left on device ... # sync # umount /dev/sdb1
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Awas |
---|---|
This is usually good enough for your USB memory stick. But this is not perfect. Most parts of erased filenames and their attributes may be hidden and remain in the filesystem. |
Even if you have accidentally deleted a file, as long as that file is still being used by some application (read or write mode), it is possible to recover such a file.
Misalnya, coba yang berikut ini
$ echo foo > bar $ less bar $ ps aux | grep ' less[ ]' bozo 4775 0.0 0.0 92200 884 pts/8 S+ 00:18 0:00 less bar $ rm bar $ ls -l /proc/4775/fd | grep bar lr-x------ 1 bozo bozo 64 2008-05-09 00:19 4 -> /home/bozo/bar (deleted) $ cat /proc/4775/fd/4 >bar $ ls -l -rw-r--r-- 1 bozo bozo 4 2008-05-09 00:25 bar $ cat bar foo
Execute on another terminal (when you have the lsof
package installed) as follows.
$ ls -li bar 2228329 -rw-r--r-- 1 bozo bozo 4 2008-05-11 11:02 bar $ lsof |grep bar|grep less less 4775 bozo 4r REG 8,3 4 2228329 /home/bozo/bar $ rm bar $ lsof |grep bar|grep less less 4775 bozo 4r REG 8,3 4 2228329 /home/bozo/bar (deleted) $ cat /proc/4775/fd/4 >bar $ ls -li bar 2228302 -rw-r--r-- 1 bozo bozo 4 2008-05-11 11:05 bar $ cat bar foo
Files with hardlinks can be identified by "ls -li
".
$ ls -li total 0 2738405 -rw-r--r-- 1 root root 0 2008-09-15 20:21 bar 2738404 -rw-r--r-- 2 root root 0 2008-09-15 20:21 baz 2738404 -rw-r--r-- 2 root root 0 2008-09-15 20:21 foo
Both "baz
" and "foo
" have link counts
of "2" (>1) showing them to have hardlinks. Their inode numbers are common "2738404". This means they
are the same hardlinked file. If you do not happen to find all hardlinked
files by chance, you can search it by the inode, e.g., "2738404" as the following.
# find /path/to/mount/point -xdev -inum 2738404
With physical access to your PC, anyone can easily gain root privilege and access all the files on your PC (see Bagian 4.6.4, “Securing the root password”). This means that login password system can not secure your private and sensitive data against possible theft of your PC. You must deploy data encryption technology to do it. Although GNU privacy guard (see Bagian 10.3, “Data security infrastructure”) can encrypt files, it takes some user efforts.
Dm-crypt facilitates automatic data encryption via native Linux kernel modules with minimal user efforts using device-mapper.
Tabel 9.25. List of data encryption utilities
paket | popcon | ukuran | deskripsi |
---|---|---|---|
cryptsetup
|
V:41, I:77 | 407 | utilities for encrypted block device (dm-crypt / LUKS) |
cryptmount
|
V:4, I:5 | 228 | utilities for encrypted block device (dm-crypt / LUKS) with focus on mount/unmount by normal users |
fscrypt
|
V:0, I:0 | 4688 | utilities for Linux filesystem encryption (fscrypt) |
libpam-fscrypt
|
V:0, I:0 | 4904 | PAM module for Linux filesystem encryption (fscrypt) |
![]() |
Perhatian |
---|---|
Data encryption costs CPU time etc. Encrypted data becomes inaccessible if its password is lost. Please weigh its benefits and costs. |
![]() |
Catatan |
---|---|
Entire Debian system can be installed on a encrypted disk by the debian-installer (lenny or newer) using dm-crypt/LUKS and initramfs. |
![]() |
Tip |
---|---|
See Bagian 10.3, “Data security infrastructure” for user space encryption utility: GNU Privacy Guard. |
You can encrypt contents of removable mass devices, e.g. USB memory stick on
"/dev/sdx
", using dm-crypt/LUKS. You
simply format it as the following.
# fdisk /dev/sdx ... "n" "p" "1" "return" "return" "w" # cryptsetup luksFormat /dev/sdx1 ... # cryptsetup open /dev/sdx1 secret ... # ls -l /dev/mapper/ total 0 crw-rw---- 1 root root 10, 60 2021-10-04 18:44 control lrwxrwxrwx 1 root root 7 2021-10-04 23:55 secret -> ../dm-0 # mkfs.vfat /dev/mapper/secret ... # cryptsetup close secret
Then, it can be mounted just like normal one on to
"/media/username/disk_label
", except
for asking password (see Bagian 10.1.7, “Removable storage device”) under
modern desktop environment using the udisks2
package.
The difference is that every data written to it is encrypted.
You may alternatively format media in different filesystem, e.g., ext4 with
"mkfs.ext4 /dev/mapper/sdx1
". If btrfs is used instead,
the udisks2-btrfs
package needs to be installed. For
these filesystems, the file ownership and permissions may need to be
configured.
![]() |
Catatan |
---|---|
If you are really paranoid for the security of data, you may initialize
device with " |
Let's assume that your original "/etc/fstab
" contains the
following.
/dev/sda7 swap sw 0 0
You can enable encrypted swap partition using dm-crypt by as the following.
# aptitude install cryptsetup # swapoff -a # echo "cswap /dev/sda7 /dev/urandom swap" >> /etc/crypttab # perl -i -p -e "s/\/dev\/sda7/\/dev\/mapper\/cswap/" /etc/fstab # systemctl restart cryptdisks ... # swapon -a
An encrypted disk partition created with dm-crypt/LUKS on
"/dev/sdc5
" can be mounted onto "/mnt
"
as follows:
$ sudo cryptsetup open /dev/sdc5 ninja --type luks Enter passphrase for /dev/sdc5: **** $ sudo lvm lvm> lvscan inactive '/dev/ninja-vg/root' [13.52 GiB] inherit inactive '/dev/ninja-vg/swap_1' [640.00 MiB] inherit ACTIVE '/dev/goofy/root' [180.00 GiB] inherit ACTIVE '/dev/goofy/swap' [9.70 GiB] inherit lvm> lvchange -a y /dev/ninja-vg/root lvm> exit Exiting. $ sudo mount /dev/ninja-vg/root /mnt
Debian distributes modularized Linux kernel as packages for supported architectures.
If you are reading this documentation, you probably don't need to compile Linux kernel by yourself.
Many Linux features are configurable via kernel parameters as follows.
Kernel parameters initialized by the bootloader (see Bagian 3.1.2, “Stage 2: the boot loader”)
Kernel parameters changed by sysctl
(8) at runtime for
ones accessible via sysfs (see Bagian 1.2.12, “procfs and sysfs”)
Module parameters set by arguments of modprobe
(8) when a
module is activated (see Bagian 9.7.3, “Mounting the disk image file”)
See "The Linux kernel user’s and administrator’s guide » The kernel’s command-line parameters" for the detail.
Most normal programs don't need kernel
headers and in fact may break if you use them directly for compiling. They
should be compiled against the headers in
"/usr/include/linux
" and
"/usr/include/asm
" provided by the
libc6-dev
package (created from the
glibc
source package) on the Debian system.
![]() |
Catatan |
---|---|
For compiling some kernel-specific programs such as the kernel modules from
the external source and the automounter daemon ( |
Debian has its own method of compiling the kernel and related modules.
Tabel 9.26. List of key packages to be installed for the kernel recompilation on the Debian system
paket | popcon | ukuran | deskripsi |
---|---|---|---|
build-essential
|
I:500 | 20 | essential packages for building Debian packages: make ,
gcc , … |
bzip2
|
V:147, I:973 | 122 | compress and decompress utilities for bz2 files |
libncurses5-dev
|
I:113 | 6 | developer's libraries and docs for ncurses |
git
|
V:312, I:494 | 36515 | git: distributed revision control system used by the Linux kernel |
fakeroot
|
V:32, I:518 | 228 | provide fakeroot environment for building package as non-root |
initramfs-tools
|
V:442, I:989 | 112 | tool to build an initramfs (Debian specific) |
dkms
|
V:99, I:210 | 295 | dynamic kernel module support (DKMS) (generic) |
module-assistant
|
V:1, I:30 | 391 | helper tool to make module package (Debian specific) |
devscripts
|
V:8, I:54 | 2654 | helper scripts for a Debian Package maintainer (Debian specific) |
If you use initrd
in Bagian 3.1.2, “Stage 2: the boot loader”, make sure to read the related
information in initramfs-tools
(8),
update-initramfs
(8), mkinitramfs
(8)
and initramfs.conf
(5).
![]() |
Awas |
---|---|
Do not put symlinks to the directories in the source tree
(e.g. " |
![]() |
Catatan |
---|---|
When compiling the latest Linux kernel on the Debian
The dynamic kernel module support (DKMS) is a new distribution independent framework designed to allow individual kernel modules to be upgraded without changing the whole kernel. This is used for the maintenance of out-of-tree modules. This also makes it very easy to rebuild modules as you upgrade kernels. |
For building custom kernel binary packages from the upstream kernel source,
you should use the "deb-pkg
" target provided by it.
$ sudo apt-get build-dep linux $ cd /usr/src $ wget http://www.kernel.org/pub/linux/kernel/v3.11/linux-version.tar.bz2 $ tar -xjvf linux-version.tar.bz2 $ cd linux-version $ cp /boot/config-version .config $ make menuconfig ... $ make deb-pkg
![]() |
Tip |
---|---|
The linux-source-version package provides the Linux
kernel source with Debian patches as
" |
For building specific binary packages from the Debian kernel source package,
you should use the
"binary-arch_architecture_featureset_flavour
"
targets in "debian/rules.gen
".
$ sudo apt-get build-dep linux $ apt-get source linux $ cd linux-3.* $ fakeroot make -f debian/rules.gen binary-arch_i386_none_686
See further information:
Debian Wiki: KernelFAQ
Debian Wiki: DebianKernel
Debian Linux Kernel Handbook: https://kernel-handbook.debian.net
The hardware driver is the code running on the main CPUs of the target
system. Most hardware drivers are available as free software now and are
included in the normal Debian kernel packages in the main
area.
The firmware is the code or data loaded on the device attach to the target system (e.g., CPU microcode, rendering code running on GPU, or FPGA / CPLD data, …). Some firmware packages are available as free software but many firmware packages are not available as free software since they contain sourceless binary data. Installing these firmware data is essential for the device to function as expected.
The firmware data packages containing data loaded to the volatile memory on the target device.
firmware-linux-free (main
)
firmware-linux-nonfree (non-free
)
firmware-linux-* (non-free
)
*-firmware (non-free
)
intel-microcode (non-free
)
amd64-microcode (non-free
)
The firmware update program packages which update data on the non-volatile memory on the target device.
fwupd (main
): Firmware
update daemon which downloads firmware data from Linux Vendor Firmware Service.
gnome-firmware (main
): GTK front end for fwupd
plasma-discover-backend-fwupd (main
): Qt front end for
fwupd
Please note that non-free
and contrib
packages are not part of the Debian system. The access configuration to
enable and to disable the non-free
and
contrib
areas is described in Bagian 2.1.4, “Debian archive basics”. You should be aware of negatives
associated with the use of the non-free
and
contrib
packages as described in Bagian 2.1.5, “Debian is 100% free software”.
Please also note that the firmware data downloaded by fwupd from Linux Vendor Firmware Service and
loaded to the running Linux kernel may be non-free
.
Use of virtualized system enables us to run multiple instances of system simultaneously on a single hardware.
There are several virtualization and emulation tool platforms.
Complete hardware emulation packages such as ones installed by the games-emulator metapackage
Mostly CPU level emulation with some I/O device emulations such as QEMU
Mostly CPU level virtualization with some I/O device emulations such as Kernel-based Virtual Machine (KVM)
OS level container virtualization with the kernel level support such as LXC (Linux Containers), Docker, ...
OS level filesystem access virtualization with the system library call override on the file path such as chroot
OS level filesystem access virtualization with the system library call override on the file ownership such as fakeroot
OS API emulation such as Wine
Interpreter level virtualization with its executable selection and run-time library overrides such as virtualenv and venv for Python
The container virtualization uses Bagian 4.7.4, “Linux security features” and it is the backend technology of Bagian 7.6, “Sandbox”.
Here are some packages to help you to setup the virtualized system.
Tabel 9.27. List of virtualization tools
paket | popcon | ukuran | deskripsi |
---|---|---|---|
schroot
|
V:7, I:9 | 2708 | specialized tool for executing Debian binary packages in chroot |
sbuild
|
V:1, I:4 | 271 | tool for building Debian binary packages from Debian sources |
debootstrap
|
V:5, I:62 | 298 | bootstrap a basic Debian system (written in sh) |
cdebootstrap
|
V:0, I:2 | 116 | bootstrap a Debian system (written in C) |
virt-manager
|
V:10, I:43 | 2298 | Virtual Machine Manager: desktop application for managing virtual machines |
libvirt-clients
|
V:46, I:64 | 1130 | programs for the libvirt library |
games-emulator
|
I:0 | 26 | games-emulator: Debian's emulators for games |
bochs
|
V:0, I:1 | 7194 | Bochs: IA-32 PC emulator |
qemu
|
I:31 | 96 | QEMU: fast generic processor emulator |
qemu-system
|
I:21 | 97 | QEMU: full system emulation binaries |
qemu-user
|
V:0, I:11 | 89683 | QEMU: user mode emulation binaries |
qemu-utils
|
V:11, I:108 | 6077 | QEMU: utilities |
qemu-kvm
|
V:8, I:55 | 107 | KVM: full virtualization on x86 hardware with the hardware-assisted virtualization |
virtualbox
|
V:11, I:14 | 107018 | VirtualBox: x86 virtualization solution on i386 and amd64 |
xen-tools
|
V:0, I:4 | 727 | tools to manage debian XEN virtual server |
wine
|
V:16, I:76 | 191 | Wine: Windows API Implementation (standard suite) |
dosbox
|
V:2, I:18 | 2702 | DOSBox: x86 emulator with Tandy/Herc/CGA/EGA/VGA/SVGA graphics, sound and DOS |
dosemu
|
V:0, I:2 | 4891 | DOSEMU: The Linux DOS Emulator |
lxc
|
V:11, I:14 | 18971 | Linux containers user space tools |
python3-venv
|
V:2, I:50 | 6 | venv for creating virtual python environments (system library) |
python3-virtualenv
|
V:9, I:64 | 410 | virtualenv for creating isolated virtual python environments |
python3-pipx
|
I:0 | NOT_FOUND | pipx for installing python applications in isolated environments |
See Wikipedia article Comparison of platform virtual machines for detail comparison of different platform virtualization solutions.
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Catatan |
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Default Debian kernels support KVM since
|
Typical work flow for virtualization involves several steps.
Create an empty filesystem (a file tree or a disk image).
The file tree can be created by "mkdir -p
/path/to/chroot
".
The raw disk image file can be created with dd
(1) (see
Bagian 9.7.1, “Making the disk image file” and Bagian 9.7.5, “Making the empty disk image file”).
qemu-img
(1) can be used to create and convert disk image
files supported by QEMU.
The raw and VMDK file format can be used as common format among virtualization tools.
Mount the disk image with mount
(8) to the filesystem
(optional).
For the raw disk image file, mount it as loop device or device mapper devices (see Bagian 9.7.3, “Mounting the disk image file”).
For disk images supported by QEMU, mount them as network block device (see Bagian 9.11.3, “Mounting the virtual disk image file”).
Populate the target filesystem with required system data.
The use of programs such as debootstrap
and
cdebootstrap
helps with this process (see Bagian 9.11.4, “Chroot system”).
Use installers of OSs under the full system emulation.
Run a program under a virtualized environment.
chroot provides basic virtualized environment enough to compile programs, run console applications, and run daemons in it.
QEMU provides cross-platform CPU emulation.
QEMU with KVM provides full system emulation by the hardware-assisted virtualization.
VirtualBox provides full system emulation on i386 and amd64 with or without the hardware-assisted virtualization.
For the raw disk image file, see Bagian 9.7, “The disk image”.
For other virtual disk image files, you can use
qemu-nbd
(8) to export them using network block device protocol and mount
them using the nbd
kernel module.
qemu-nbd
(8) supports disk formats supported by QEMU: QEMU supports
following disk formats: raw, qcow2, qcow,
vmdk, vdi, bochs, cow (user-mode Linux copy-on-write), parallels, dmg, cloop, vpc, vvfat (virtual
VFAT), and host_device.
The network block device can
support partitions in the same way as the loop
device (see Bagian 9.7.3, “Mounting the disk image file”). You
can mount the first partition of "disk.img
" as follows.
# modprobe nbd max_part=16 # qemu-nbd -v -c /dev/nbd0 disk.img ... # mkdir /mnt/part1 # mount /dev/nbd0p1 /mnt/part1
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Tip |
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You may export only the first partition of " |
If you wish to try a new Debian environment from a terminal console, I
recommend you to use chroot. This enables you
to run console applications of Debian unstable
and
testing
without usual risks associated and without
rebooting. chroot
(8) is the most basic way.
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Perhatian |
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Examples below assumes both parent system and chroot system share the same
|
Although you can manually create a chroot
(8) environment
using debootstrap
(1). But this requires non-trivial
efforts.
The sbuild package to build Debian packages
from source uses the chroot environment managed by the schroot package. It comes with helper script
sbuild-createchroot
(1). Let's learn how it works by
running it under script
(1) as follows.
$ sudo mkdir -p /srv/chroot $ sudo sbuild-createchroot -v --include=eatmydata,ccache unstable /srv/chroot/unstable-amd64-sbuild http://deb.debian.org/debian
You see how debootstrap
(8) populates system data for
unstable
environment under
"/srv/chroot/unstable-amd64-sbuild
" for a minimal build
system.
You can login to this environment using schroot
(1).
$ sudo schroot -v -c chroot:unstable-amd64-sbuild
You see how a system shell running under unstable
environment is created.
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Catatan |
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The " |
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Catatan |
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Some programs under chroot may require access to more files from the parent
system to function than |
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Tip |
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The |
If you wish to try a new GUI Desktop environment of any OS, I recommend you
to use QEMU, KVM, or
VirtualBox on a Debian
stable
system to run multiple desktop systems safely
using virtualization. These enable
you to run any desktop applications including ones of Debian
unstable
and testing
without usual
risks associated with them and without rebooting. The configuration of
these tools are relatively straight forward.
Since pure QEMU is very slow, it is recommended to accelerate it with KVM when the host system supports it.
The virtual disk image "virtdisk.qcow2
" containing a
Debian system for QEMU can be created using
debian-installer: Small CDs
as follows.
$ wget http://cdimage.debian.org/debian-cd/5.0.3/amd64/iso-cd/debian-503-amd64-netinst.iso $ qemu-img create -f qcow2 virtdisk.qcow2 5G $ qemu -hda virtdisk.qcow2 -cdrom debian-503-amd64-netinst.iso -boot d -m 256 ...
See more tips at Debian wiki: QEMU.
VirtualBox comes with Qt GUI tools and quite intuitive. Its GUI and command line tools are explained in VirtualBox User Manual and VirtualBox User Manual (PDF).
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Tip |
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Running other GNU/Linux distributions such as Ubuntu and Fedora under virtualization is a great way to learn configuration tips. Other proprietary OSs may be run nicely under this GNU/Linux virtualization, too. |
[2] More elaborate customization examples: "Vim Galore", "sensible.vim", "#vim Recommendations" ...
[3] vim-pathogen populer.