| [ .terminal ] | .A | .B | .C | .D | .E | .F | .G | .H | .I | .J | .K | .L | .M | .N | .O | .P | .Q | .R | .S | .T | .U | .V | .W | .X | .Y | .Z | .appendix | |
| If you
choose to use Linux,
you
will inevitably need to use the terminal or command line console. Some common popular shells are:
bash, csh
and tsch among several others. Unix-like
system
users are already familiar with the terminal. For
windows users, it is similar to ms-dos, only much more powerful. The real
power and appeal in
Unix
and Linux is not only in in the general free and open nature of the
software and ideas but also in the efficient use of the command line. With the
command line you
have
the flexibility to interact directly with the kernel (the core of the
system) as well as a host of other useful features. You
are open
to thousands of different options, commands and
tools that, in the end, provide a highly stable, highly configurable
and very highly functional operating environment. Most commands and some configuration
(.conf) files also have "man pages" which allow you to read about the
verbose options and descriptions available. To access man pages type: man
<command> at the terminal to read about the command, use q to
exit the dialog. Below
is a list of
*some* common
useful commands available at the bash (bourne again shell) terminal
prompt: |
Commonly used terminal commands that
span nearly all Linux distributions
| .A | .top
apropos - Apropos
searches a set of database files containing short descriptions of
system commands for keywords and displays the result on the standard
output.
example: user1@foo ]$ apropos search (this command displays a list of possible commands and their respective descriptions with the string "search" in the command or in the command description.)
example: user1@foo ]$ apropos search (this command displays a list of possible commands and their respective descriptions with the string "search" in the command or in the command description.)
| .B | .top
bcwipe - Bcwipe
repeatedly overwrites special patterns to the files to be destroyed. In normal
mode, 35 passes are used (of which 8 are random). Patterns
used were recommended in article by Peter Gutmann (http://www.cs.auckland.ac.nz/~pgut001/pubs/secure_del.html)
entitled "secure deletion of data from magnetic and solid-state
memory". In
quick mode, U.S. DoD(Department of Defence) 5200.28 standard are used
with 7 pass wiping. In custom
mode U.S. DoD 5200.28 standard are used with user defined number of
passes.
example: user1@foo ]$ bcwipe -ng -r -v /home/temp (this command will do a 35 pass; recursive; verbose DoD wipe on /home/temp. Usually, bcwipe is used on an entire drive or partition where sensitive or personal data has been kept to prevent recovery of the data if the drive or system is being sold or given to an unknown party.)
example: user1@foo ]$ bcwipe -ng -r -v /home/temp (this command will do a 35 pass; recursive; verbose DoD wipe on /home/temp. Usually, bcwipe is used on an entire drive or partition where sensitive or personal data has been kept to prevent recovery of the data if the drive or system is being sold or given to an unknown party.)
| .C | .top
example: user1@foo ]$ cd /etc/X11 (this command changes the current working directory (cwd) to /etc/X11)
cp - Copy files, used for copying files to and from different directories.
example: user1@foo ]$ cp ~/foo.txt /mnt/storage (this command copies the file "foo.txt" from /home/user1/foo.txt to /mnt/storage/foo.txt)
dd - Copy a file, converting and formatting according to the specified options.
example: root@foo ]# dd if=/dev/dvd
of=dvd_foo.iso (this command creates an iso image
from the device /dev/dvd and writes to a local file (dvd_foo.iso) in
the (cwd) current working directory.)
df - Displays total disk usage for mounted filesystems.
example: user1@foo ]$ df -h (this command displays the used/free space ratio on all currently mounted filesystems.)
diff - In the
simplest case, diff compares the contents of the two files from-file
and to-file. A
file name of - stands for text read from the standard input. As a
special case, diff - - compares a copy of standard input to itself. If
from-file is a directory and to-file is not, diff compares the file in
from-file whose file name is that of to-file, and vice versa. The
non-directory file must not be -. If
both from-file and to-file are directories, diff
compares corresponding files in both directories, in alphabetical
order; this comparison is not recursive unless the -r or --recursive
option is given. diff never compares the actual contents of a directory
as if it were a file. The file
that is fully specified may not be
standard input, because standard input is nameless
and the notion of ‘‘file with the same name’’ does not apply. diff
options begin with -, so normally from-file and to-file may not begin
with -. However,
-- as an argument by itself treats the remaining arguments as file
names even if they begin with -.
example: user1@foo ]$ diif /var/log/messages
/var/log/messages.saved (this command displays the
differences between the 2 files.)du - Displays total disk usage for named directories.
example: user1@foo ]$ du -chs /home (this command displays in user readable format the space usage for the directory /home)
exit - Exits a login terminal or a session as a certain user.
example: root@foo ]# exit (this command will exit the current (# root) shell and drop the user back to the ($ user) prompt, if logged in via su or su -. )
fdisk - Fdisk is a powerful disk partitioning utility.
example: root@foo ]# fdisk -l (this command lists the currently
detected partitions and partition types. Use the man page to understand
the full scope of this very useful and powerful command.)
find - Find searches a given directory structure for a named string and displays pertinent results.
example: user1@foo ]$ find ~ -name foo (this searches the user1's home and
any subdirectories for any occurance of "foo" and displays the results,
if any.)
fsck - Fsck initiates filesystem integrity check and repair on unmounted filesystems.
example: root@foo ]# fsck -y /dev/hda1 (this command forces a filesystem
check on the partition hda1 and fixes any errors encountered without prompting the user
to "ok" any confimation dialogs. use
with caution and read the man
page.)
fuser - Identify processes using files or sockets.
example: user1@foo ]$ fuser -m /mnt/floppy (this command searches for processes using /mnt/floppy and displays the results.)
grep - Grep
searches the
named input file(s) (or standard input if no files are named, or the
file
name - is given) for lines containing a match to the given pattern.
By
default, grep prints the matching lines.
example: user1@foo ]$ rpm -qa | grep foo (this command searches the rpm
database for a string "foo" and prints any matches it encounters.)hostname - Hostname
is the program that is used to either set or display the current host,
domain or node name of the system. These
names are used by many of the networking programs to identify the
machine. The
domain name is also used by NIS/YP.
example: user1@foo ]$ hostname (this command displays the current
hostname.)ifconfig - Ifconfig
is used to configure the kernel-resident network interfaces. It is used
at boot time to set up interfaces as necessary. After
that, it is usually only needed when debugging or when system tuning is
needed. If
no arguments are given, ifconfig displays the status of the currently
active interfaces. If a
single interface argument is given, it displays the status of the given
interface only; if a single -a argument is given, it displays the
status of all interfaces, even those that are down. Otherwise,
it configures an interface.
example: user1@foo ]$ ifconfig (this command issued by itself will
print all currently configured network interfaces.)ifdown - Brings a network interface down (offline) manually.
example: user1@foo ]$ ifdown eth0 (this command brings the network interface 'eth0' down or offline.)
ifup - Brings a network interface up (online) manually.
example: user1@foo ]$ ifup eth0 (this command brings the network interface 'eth0' up or online.)
jwhois - Jwhois
searches Whois servers for the object on the command line. The host
to query is taken from a global configuration file, a configuration
file specified on the command line, or selected directly on the command
line.
example: user1@foo ]$ jwhois google.com (this command queries the whois
database for the contact and domain registration details of google.com.)kill - Terminate a currently running or rogue process. also see: killall
example: user1@foo ]$ kill -9 27068 (this command terminates a process with a process id of 27058 found by using the command ps aux.)
last - Lists
users who have recently logged into or out of the system. Also displays
time, date and duration.
example: user1@foo ]$ last (this command lists all of the users
who have recently logged into or out of the system.)
less - Less is a
program similar to more, but which allows backward movement in the file
as well as forward movement. Also, less
does not have to read the entire input file
before starting, so with large input files it starts up
faster than text editors like vi. Less uses
termcap (or terminfo on some systems), so it can run on a variety of
terminals. There
is even limited support for hardcopy terminals. (on a hardcopy terminal, lines which
should be printed at the top of the screen are prefixed with a caret.)
example: user1@foo ]$ less -p CPU
/var/log/dmesg (this command searches
/var/log/dmesg for any instance of the string 'CPU' and displays those
lines with 'CPU' highlighted.)
ls - Lists files, directories and thier respective permissions (depending on the switches and options used.)
example: user1@foo ]$ ls -als (this command lists all of the
files and subdirectories in the current working directory (cwd) and
their
respective permissions. to slow down long directory listings use: ls
-als | less use q to exit.)
lspci - Lspci is a utility for displaying information about all PCI buses in the system and all devices connected to them.)
lspci - Lspci is a utility for displaying information about all PCI buses in the system and all devices connected to them.)
example: user1@foo ]$ lspci -v (this command lists all of the
pci devices detected by the system in verbose mode.)
lsusb - Lsusb is a utility for displaying information about USB buses in the system and the devices connected to them. To use lsusb make sure you have usb-utils package installed.)
lsusb - Lsusb is a utility for displaying information about USB buses in the system and the devices connected to them. To use lsusb make sure you have usb-utils package installed.)
example: user1@foo ]$ lsusb -v (this command lists all of the usb
devices detected by the system in verbose mode.)
man - Man
formats and displays the
on-line manual pages. If you
specify section, man only looks in
that section of the manual. name is normally the name of the
manual page, which is typically the name of a command, function, or
file. However,
if name contains a slash (/)
then man interprets it as a file specification, so that you
can do man ./foo.5 or even man /cd/foo/bar.1.gz.
example: user1@foo ]$ man sudo (this command will display the sudo
command man page and a verbose list of options and usage.)mount - Mount a filesystem. see also: umount.
example: root@foo ]# mount -t ext3 /dev/hdk3 /mnt/foo (this command mounts partition 3 on
the hard disk /dev/hdk on /mnt/foo where the user can then access it
with the proper rwx permissions. automounting filesystems can be taken
care of in /etc/fstab)
mv - Move files
from one directory to
another. (similar to cut) this option deletes
the file from the
original location and moves it to another, it is also used to rename
files.)
example: user1@foo ]$ mv foo.rpm foo2.rpm (this command renames "foo.rpm" to
"foo2.rpm" within the same directory.)nano - Nano is a
small, free and friendly editor which aims to replace pico, the
default editor included in the non-free pine package. Rather
than just
copying pico’s look and feel, nano also implements some missing (or
disabled by default) features in pico, such as "search and replace" and
"go to line number".
.example: root@foo ]# nano /var/log/dmesg (this command displays the text file /var/log/dmesg in a terminal window and presents it for editing or reading.)
.example: root@foo ]# nano /var/log/dmesg (this command displays the text file /var/log/dmesg in a terminal window and presents it for editing or reading.)
octave - A high-level interactive language for numerical computations.
example: root@foo ]# octave --help (this command will display the
options for the octave command.)
passwd - Passwd is
used to update a user’s authentication token(s). Passwd is
configured to work through the Linux-PAM API. Essentially,
it
initializes itself as a "passwd" service with Linux-PAM and utilizes
configured password modules to authenticate and then update a user’s
password..
example: user1@foo ]$ passwd newuser (this command prompts the issuer to provide a new password for the given user and then updates the password database accordingly replacing the previous password with the new one.)
example: user1@foo ]$ passwd newuser (this command prompts the issuer to provide a new password for the given user and then updates the password database accordingly replacing the previous password with the new one.)
ps - Prints a list of currently running processes, their respective owners and process id's.
example: user1@foo ]$ ps aux (this command displays the curently running processes among other important data about the respective processes.)
pwd - Print the name of the working directory.
example: user1@foo ]$ pwd (this command prints the current path/working directory in your shell, such as: /home/user1/foo)
quota - Displays a
list of users’ disk usage and limits. By default only the user quotas
are printed. Quota
reports the quotas of all the filesystems listed in /etc/mtab. For
filesystems that are NFS-mounted a call to the rpc.rquotad on the
server machine is performed to get the information.
example: root@foo ]# quota user1 (this command displays the requested
users disk quota usage and limits.)rm - Remove files and/or directories.
example: user1@foo ]$ rm -rf ~/temp (this command removes the directory /home/user1/temp)
slocate - Security
enhanced version of the
GNU locate command. secure locate provides a secure way to index and
quickly search for files on your system. It uses
incremental encoding
just like GNU locate to compress its database to make searching faster,
but it will also store file permissions
and ownership so that users will not see files they do not have access
to..
example: user1@foo ]$ slocate gimp (this command searches a secure
database starting at / for the given string. note: you must first run
the command updatedb or slocate -u before using slocate.)ssh - Starts the
secure shell connection with a system running the sshd (secure shell
daemon).
example: user1@foo ]$ ssh 192.168.0.10 (this command initiates a secure shell connection between the localhost computer and the internal local network computer at 192.168.0.10.)
example: user1@foo ]$ ssh 192.168.0.10 (this command initiates a secure shell connection between the localhost computer and the internal local network computer at 192.168.0.10.)
stat - Display file or filesystem status.
example: user1@foo ]$ stat /home (this command displays the status of the /home directory such as, block size, inodes, links, access and last modified date(s), among other user definable variables.)
su - Substitute user command. most commonly used to run commands / daemons which require root privlages, view / alter certain directories, files and log files.
example: user1@foo ]$ su - (this command will prompt the user
for the root password and, if supplied correctly, logs the user into
roots profile. the - denotes that the user should inherit roots profile
and path. this is quite helpful when issuing commands from many
directories without typing the entire path to the command. system
administrators should see the "sudo" command for extending certain
privlages to users who do not need or cannot be trusted with the root
password.)
sudo - Super user
"do" allows a user to
issue some commands which require elevated privlages as defined in
/etc/sudoers but does not require knowledge of the root password.
example: user1@foo ]$ sudo mount -t ext3
/dev/hdk3 /mnt/foo (this command allows a normal user
with sudoer privlages to issue a command that requires elevated
privlages to run. the user will be required to enter their own password
to complete the command by default, this option can be changed to not
require a password. see: man
sudoers)
tar - The tar command compresses or uncompresses tar or tar.gz archived files and directory structures.
example: user1@foo ]$ tar -xvfz foo.tar.gz (this command uncompresses the file foo.tar.gz into the cwd.)
uname - Print certain system information such as: currently running kernel, hostname, etcetera.
example: user1@foo ]$ uname -a (this command prints information about the currently running kernel as well as other information.)
useradd - When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line and the default values from the system. Depending on command line options, the useradd command will update system files and may also create the new user’s home directory and copy initial files. The version provided with Red Hat Linux will create a group for each user added to the system by default..
example: root@foo ]# useradd -d -g 500 newuser (this command adds a new user to the system with a home directory of /home/newuser and a group id of 500. Alternatively, you can also use somehing like 'ftp' instead of '500' to specify what group(s) you want to add the new user to. see also: man adduser and userdel / deluser.)
vi - Vi is, quite simply, a programmers terminal-based text editor. Vi is on every Unix / Linux system you will ever encounter and is very powerful. It can be used for high level programming or simply to edit a text file, save and close it.
example: user1@foo ]$ vi /var/log/dmesg (this command displays the text file /var/log/dmesg in a terminal window and prsents it for editing or reading.)
wc - The wc command prints newline, word, and byte counts for each file, and a total line if more than one file is specified. With no file, or when file is -, read standard input.
example: user1@foo ]$ wc -l /var/log/dmesg (this command displays the total number of lines in the text file /var/log/dmesg.)
tar - The tar command compresses or uncompresses tar or tar.gz archived files and directory structures.
example: user1@foo ]$ tar -xvfz foo.tar.gz (this command uncompresses the file foo.tar.gz into the cwd.)
uname - Print certain system information such as: currently running kernel, hostname, etcetera.
example: user1@foo ]$ uname -a (this command prints information about the currently running kernel as well as other information.)
useradd - When invoked without the -D option, the useradd command creates a new user account using the values specified on the command line and the default values from the system. Depending on command line options, the useradd command will update system files and may also create the new user’s home directory and copy initial files. The version provided with Red Hat Linux will create a group for each user added to the system by default..
example: root@foo ]# useradd -d -g 500 newuser (this command adds a new user to the system with a home directory of /home/newuser and a group id of 500. Alternatively, you can also use somehing like 'ftp' instead of '500' to specify what group(s) you want to add the new user to. see also: man adduser and userdel / deluser.)
vi - Vi is, quite simply, a programmers terminal-based text editor. Vi is on every Unix / Linux system you will ever encounter and is very powerful. It can be used for high level programming or simply to edit a text file, save and close it.
example: user1@foo ]$ vi /var/log/dmesg (this command displays the text file /var/log/dmesg in a terminal window and prsents it for editing or reading.)
wc - The wc command prints newline, word, and byte counts for each file, and a total line if more than one file is specified. With no file, or when file is -, read standard input.
example: user1@foo ]$ wc -l /var/log/dmesg (this command displays the total number of lines in the text file /var/log/dmesg.)
who - Thows who is currently logegd on to the system.
example: user1@foo ]$ who -last (this command displays verbose output of the users and processes logged into the system.)
whois - (see jwhois.)
xrandr - Xrandr is
used to set the screen size, orientation and/or reflection. The -s
option is a small integer index used to specify which size the screen
should be set to. To find
out what sizes are available, use the -q option, which reports the
sizes available, the current rotation, and the possible rotations and
reflections. The
default size is the first size specified in the list. The -o
option is used to specify the orientation of the screen, and can be one
of "normal inverted left right 0 1 2 3". The -x
option instructs the server to reflect the screen on the X axis. The -y
option instructs the server to reflect the screen on the Y axis. Reflection
is applied after rotation. The -help
option prints out a usage summary. The
--verbose option tells you what xrandr is doing, selects for events,
and tells you when events are received to enable debugging.
example: user1@foo ]$ xrandr --verbose (this command shows the current
reflection, rotation and other information.)xwininfo - Xwininfo
is a utility for displaying information about windows. Various
information is displayed depending on which options are selected. If no
options are chosen, -stats is assumed. The
user has the option of selecting the target window with the mouse (by
clicking any mouse button in the desired window) or by specifying its
window id on the command line with the -id option. Or instead
of specifying the window by its id number, the -name option may be used
to specify which window is desired by name. There is
also a special -root option to quickly obtain information on the
screen’s root window.
example: user1@foo ]$ xwininfo (this command displays the geometry
for the specified window.)yum - Yum is a
powerful, interactive, and automated package update / query / install
program which can be used for maintaining systems using rpm (Redhat
Package Manager).
example: root@foo ]# yum --exclude=kernel*
update (this common command initiates a
full system update, while telling yum to exclude / ignore
any kernel packages.)
| .Z
| .top
zip - Zip is a
compression and file packaging utility for Unix, VMS, MSDOS, OS/2,
Windows NT, Minix, Atari and Macintosh, Amiga and Acorn RISC OS. It is
analogous to a combination of the UNIX commands tar(1) and compress(1)
and is compatible with PKZIP (Phil Katz’s ZIP for MSDOS systems). A companion program (unzip(1L)),
unpacks zip archives. The zip
and unzip(1L) programs can work with archives produced by PKZIP, and
PKZIP and PKUNZIP can work with archives produced by zip. Zip
version 2.3 is compatible with PKZIP 2.04. Note that PKUNZIP 1.10
cannot extract files produced by PKZIP 2.04 or zip 2.3. You must
use PKUNZIP 2.04g or unzip 5.0p1 (or later versions) to extract them.
example: user1@foo ]$ zip -r foo1 foo2 (this command creates the archive foo2.zip, containing all the files and directories in the directory foo1 that is contained within the current directory.)
example: user1@foo ]$ zip -r foo1 foo2 (this command creates the archive foo2.zip, containing all the files and directories in the directory foo1 that is contained within the current directory.)
[ .appendix ] .top
Pipe Symbol - [ | ] This symbol is used to separate commands on a single line.
example: user1@foo ]$ rpm -qa | grep foo (this command runs the first half, then "pipes" the output through the second.)
Tab Key- Tab key is used to auto-complete commands, filenames, directory paths at the command prompt.
example: user1@foo ]$ chm (hitting tab here would auto-complete the command "chmod")
Arrow Keys - Up and down arrow keys can be used to scroll recently issued commands at the command prompt.
example: user1@foo ]$ (hitting the up or down arrow keys at the command prompt scrolls through your issued command history)
Tilde - [ ~ ] The tilde is used to denote the currently logged in users home dir.
example: user1@foo ]$ cd ~/Desktop (this command would send you to /home/user1/Desktop)
&& Operator
- This
operator is used when
issuing more than one command on a single line. Similar to
; but more effective because if any
command should fail anywhere in the sequence the user will be dropped
back to a prompt rather than attempting to complete the command
sequence and possibly causing system instability or damage.
example: user1@foo ]$ cd /usr/src/foo
&& ./configure && make && make install (this
initiates a command to change
current working directory (cwd) to /usr/src/foo and, if successful,
proceed with the next command and so on. if any command should fail,
you will be dropped down to a command prompt with a resulting error
message.)