Linux Command

File Commands

ls                       -list directory
ls -al                   -formatted listing with hidden files
ls -ltr                  -formatted listing ordered by time
cd dir                   -change to directory
cd -                     -go to directory in previously
cd                       -go to home directory
pwd                      -show current directory path
mkdir dir                -make directory dir
rm file                  -delete file
rm -r dir                -delete directory dir
rm -f file               -force remove file
rm -rf dir               -force remove directory dir
cp file1 file2           -copy file1 to file2
cp -r dir1 dir2          -copy dir1 to dir2; create dir2 if it doesn’t exist
mv file1 file2           -rename/move file1 to file2 if file2 is an existing dir, moves file1
into dir file2
ln -s file link          -create symbolic link link to file
touch file               -create or update file
cat > file               -places standard input into file
more file                -output the contents of file
head file                -output the first 10 lines of file
tail file                -output the last 10 lines of file
tail -f file             -output the contents of file as it grows, starting with the last 10 lines

Process Management

ps                       -display your currently active processes
top                      -display all running processes
kill pid                 -kill process id pid
killall proc             -kill all processes named proc
bg                       -lists stopped or background jobs; resume a stopped job in the background
fg                       -brings the most recent job to foreground
fg n                     -brings job n to the foreground

File Permissions

chmod octal file         -change the permissions of file to octal, which can be found separately for user, group, and world by adding:
● 4 – read (r)
● 2 – write (w)
● 1 – execute (x)
Examples:
chmod 777                -read, write, execute for all
chmod 755                -rwx for owner, rx for group and world For more options, see man chmod.
chown user:group file    -change the owner and group for a file

SSH

ssh user@host            -connect to host as user
ssh -p port user@host    -connect to host on port port as user
ssh-copy-id user@host    -add your key to host for user to enable a keyed or passwordless 

Searching

grep pattern files       -search for pattern in files
grep -r pattern dir      -search recursively for pattern in dir
command | grep pattern   -search for pattern in the output of command
locate file              -find all instances of file
find . file              -find file within current directory
find / file              -find file within whole system

System Info

date                      -show the current date and time
cal                       -show this month’s calendar
uptime                    -show current uptime
w                         -display who is online
whoami                    -who you are logged in as
finger user               -display information about user
uname -a                  -show kernel information
cat /proc/cpuinfo         -cpu information
cat /proc/meminfo         -memory information
man command               -show the manual for command
df                        -show disk usage
du                        -show directory space usage
du -sk | sort -n          -show sum of each directory space usage sorted by number in KB
free                      -show memory and swap usage
whereis app               -show possible locations of app
which app                 -show which app will be run by default

Compression

tar cf file.tar files     – create a tar named file.tar containing files
tar xf file.tar           – extract the files from file.tar
tar czf file.tar.gz files – create a tar with Gzip compression
tar xzf file.tar.gz       – extract a tar using Gzip
tar cjf file.tar.bz2      – create a tar with Bzip2 compression
tar xjf file.tar.bz2      – extract a tar using Bzip2
gzip file                 – compresses file and renames it to file.gz
gzip -d file.gz           – decompresses file.gz back to file

Network

ping host                 – ping host and output results
whois domain              – get whois information for domain
dig domain                – get DNS information for domain
dig -x host               – reverse lookup host
wget file                 – download file
wget -c file              – continue a stopped download

Installation

Install from source:
./configure
make
make install
dpkg -i pkg.deb           – install a package (Debian)
rpm -Uvh pkg.rpm          – install a package (RPM)

Shortcuts

Ctrl+C                    – halts the current command
Ctrl+Z                    – stops the current command, resume with fg in the foreground
or bg in the background
Ctrl+D                    – log out of current session, similar to exit
Ctrl+W                    – erases one word in the current line
Ctrl+U                    – erases the whole line
Ctrl+R                    – type to bring up a recent command
!!                        - repeats the last command
exit                      – log out of current session