Essential CentOS Commands You Should Know

Common commands:

Files and directories:

# cd /home
                       enter the
‘/home’ directory

# cd ..
                               go back to the parent directory

# cd ../..
                            go back two directory levels

# cd –
                                go back to the previous directory

# cp file1 file2
                   copy file1 to file2

# cp -a dir1 dir2                 copy a directory

# cp -a /tmp/dir1 .              copy a directory to the current working directory (. represents the current directory)

# ls
                                   view files in the directory

# ls -a
                               show hidden files

# ls -l
                               Show detailed information

# ls -lrt
                              Show files by time (l means detailed list, r means reverse order, t means sort by time)

# pwd
                               Show the working path

# mkdir dir1
                      Create
the ‘dir1’ directory

# mkdir dir1 dir2                Create two directories at the same time

# mkdir -p /tmp/dir1/dir2    Create a directory tree

# mv dir1 dir2
                   Move/rename a directory

# rm -f file1
                       Delete
‘file1’

# rm -rf dir1
                      Delete
the ‘dir1’ directory and its subdirectory contents

View file contents:

# cat file1
                         view the contents of a file forward starting from the first byte

# head -2 file1                   view the first two lines of a file

# more file1
                      view the contents of a long file

# tac file1
                         view the contents of a file in reverse starting from the last line

# tail -3 file1
                     view the last three lines of a file

Text processing:

# grep str /tmp/test            find “str” in the file
‘/tmp/test’

# grep ^str /tmp/test           find lines in the file
‘/tmp/test’ that begin with “str”

# grep [0-9] /tmp/test         find
all lines in the file ‘/tmp/test’ that contain numbers

# grep str -r /tmp/*             find “str” in the directory
‘/tmp’ and its subdirectories

# diff file1 file2                   find the differences between two files

# sdiff file1 file2                 display the differences between two files side by side

Find:

# find / -name file1
                                                starting from
‘/’, enter the root filesystem to search for files and directories

# find / -user user1
                                               find files and directories belonging to user
‘user1’

# find /home/user1 -name *.bin
                           in directory
‘/ home/user1’, find files ending with ‘.bin’

# find /usr/bin -type f -atime +100
                        find executable files that have not been used in the past 100 days

# find /usr/bin -type f -mtime -10
                          find files created or modified within the last 10 days

# locate *.ps
                                                         find files ending with
‘.ps’; first run the
‘updatedb’ command

# find -name ‘*.[ch]’ | xargs grep -E
‘expr’              search for
‘expr’
in all .c and .h files in the current directory and its subdirectories

# find -type f -print0 | xargs -r0 grep -F
‘expr’        search for
‘expr’
in regular files in the current directory and its subdirectories

# find -maxdepth 1 -type f | xargs grep -F
‘expr’    search for
‘expr’
in the current directory

Compression and decompression:

# bzip2 file1
                                  compress
file1

# bunzip2 file1.bz2
                       decompress
file1.bz2

# gzip file1
                                    compress
file1

# gzip -9 file1
                               compress
file1
as much as possible

# gunzip file1.gz
                           decompress
file1.gz

# tar -cvf archive.tar file1               Package file1 into
archive.tar

(-c: create an archive; -v: display the entire process; -f:
use the archive filename, required, and must be the last parameter)

# tar -cvf archive.tar file1 dir1        Package
file1 and dir1 into archive.tar

# tar -tf archive.tar
                        Show the contents of an archive

# tar -xvf archive.tar
                     Extract an archive

# tar -xvf archive.tar -C /tmp         Extract the archive to the
/tmp directory

# zip file1.zip file1
                         Create a zip-format archive

# zip -r file1.zip file1 dir1               Compress files and directories into a zip-format archive

# unzip file1.zip
                            Extract a zip-format archive to the current directory

# unzip test.zip -d /tmp/                 Extract a zip-format archive to the
/tmp directory

yum tool:

# yum -y install [package]              Download and install an rpm package

# yum localinstall [package.rpm]    Install an rpm package, using your own software repository to resolve all dependencies

# yum -y update
                             Update all rpm packages installed on the current system

# yum update [package]                 Update an rpm package

# yum remove [package]                Remove an rpm package

# yum list
                                       List all packages installed on the current system

# yum search [package]                 Search for a package in the rpm repository

# yum clean [package]
                  Clear packages from the cache directory (/var/cache/yum)

# yum clean headers
                     Delete all header files

# yum clean all
                               Delete all cached packages and header files

Network:

# ifconfig eth0
                                                                     Displays the configuration of an Ethernet card

# ifconfig eth0 192.168.1.1 netmask 255.255.255.0
           Configure the IP address of the network card

# ifdown eth0
                                                                       Disable
the ‘eth0’ network device

# ifup eth0
                                                                           Enable
the ‘eth0’ network device

# iwconfig eth1
                                                                   Displays the configuration of a wireless network card

# iwlist scan
                                                                        shows wireless networks

# ip addr show
                                                                    shows the IP address of the network interface

Other:

# su –
                                switch to root privileges (different from su)

# shutdown -h now           shut down

# shutdown -r now            reboot

# top
                                  lists the Linux tasks using the most CPU resources
(press q to quit)

# pstree
                            displays programs in a tree view

# man ping
                       View the reference manual (for example, for the ping
command)

# passwd
                         Change password

# df -h
                              Shows disk usage

# cal -3
                            Shows the previous month, the current month, and the next month

# cal 10 1988                   Shows the calendar for the specified month and year

# date –date ‘1970-01-01 UTC 1427888888
seconds’   Converts a number of seconds relative to 1970-01-01
00:00 into a time

Ctrl + u            Delete the characters from before the cursor to the beginning of the line

Ctrl + k            Delete the characters from the cursor to the end of the line

Ctrl + c            Cancel the command currently being entered on the line, equivalent to Ctrl
+ Break

Ctrl + a            Move the cursor to the beginning of the line (ahead
of line), equivalent to the usual Home key

Ctrl + e            Move the cursor to the end
of the line

Ctrl + f             Move the cursor forward by one character

Ctrl + b            Move the cursor backward by one character

Ctrl + l             Clear the screen, equivalent to running the clear command

Ctrl + r            Display the : prompt and search related command history based on user input (reverse-i-search)

Ctrl + w           Delete from the cursor position back to the beginning of the current word

Ctrl + t             Swap the two characters before the cursor

Ctrl + y            Paste the last deleted word

Ctrl + Alt + d   Show the desktop

Alt + b             Move the cursor backward to the previous word

Alt + d             Delete from the cursor position to the end of the current word

Alt + F2           Run

Alt + F4           Close the current window

Alt + F9           Minimize the current window

Alt + F10         Maximize the current window

Alt + Tab         Switch windows

Alt + hold down the left mouse button  Move the window (or scroll the mouse wheel on the bottom taskbar)

[Middle mouse button]
Paste highlighted text. Use the left mouse button to select text. Point the cursor where you want to paste the text. Click the middle mouse button to paste.

[Tab] command-line auto-completion. You can use this when working at a shell
prompt. Type the first few characters of a command or filename, then press the
[Tab] key. It will automatically complete the command or show all commands that
match what you typed.

On the desktop or in the file manager, just press /
to enter a location and open it in the file manager.

Quick search: in vi or Firefox, just press / to enter search mode.

Website links and images can be dragged directly to the desktop or a folder for immediate downloading.

Simply drag a file from the file manager into the terminal to get its full pathname in the terminal.

Click the blank area of the scroll bar with the middle mouse button, and the screen will scroll to that position.