Unix/Linux Command Reference .com
File Commands
ls โ directory listing
ls -al โ formatted listing with hidden files
cd dir - change directory to dir
cd โ change to home
pwd โ show current directory
mkdir dir โ create a directory dir
rm file โ delete file
rm -r dir โ delete directory dir
rm -f file โ force remove file
rm -rf dir โ force remove directory dir *
cp file1 file2 โ copy file1 to file2
cp -r dir1 dir2 โ copy dir1 to dir2; create dir2 if it
doesn't exist
mv file1 file2 โ rename or move file1 to file2
if file2 is an existing directory, moves file1 into
directory file2
ln -s file link โ create symbolic link link to file
touch file โ create or update file
cat > file โ places standard input into file
more file โ output the contents of file
head file โ output the first 10 lines of file
tail file โ output the last 10 lines of file
tail -f file โ output the contents of file as it
grows, starting with the last 10 lines
Process Management
ps โ display your currently active processes
top โ display all running processes
kill pid โ kill process id pid
killall proc โ kill all processes named proc *
bg โ lists stopped or background jobs; resume a
stopped job in the background
fg โ brings the most recent job to foreground
fg n โ brings job n to the foreground
File Permissions
chmod octal file โ change the permissions of file
to octal, which can be found separately for user,
group, and world by adding:
โ4 โ read (r)
โ2 โ write (w)
โ1 โ execute (x)
Examples:
chmod 777 โ read, write, execute for all
chmod 755 โ rwx for owner, rx for group and world
For more options, see man chmod.
SSH
ssh user@host โ connect to host as user
ssh -p port user@host โ connect to host on port
port as user
ssh-copy-id user@host โ add your key to host for
user to enable a keyed or passwordless login
Searching
grep pattern files โ search for pattern in files
grep -r pattern dir โ search recursively for
pattern in dir
command | grep pattern โ search for pattern in the
output of command
locate file โ find all instances of file
System Info
date โ show the current date and time
cal โ show this month's calendar
uptime โ show current uptime
w โ display who is online
whoami โ who you are logged in as
finger user โ display information about user
uname -a โ show kernel information
cat /proc/cpuinfo โ cpu information
cat /proc/meminfo โ memory information
man command โ show the manual for command
df โ show disk usage
du โ show directory space usage
free โ show memory and swap usage
whereis app โ show possible locations of app
which app โ show which app will be run by default
Compression
tar cf file.tar files โ create a tar named
file.tar containing files
tar xf file.tar โ extract the files from file.tar
tar czf file.tar.gz files โ create a tar with
Gzip compression
tar xzf file.tar.gz โ extract a tar using Gzip
tar cjf file.tar.bz2 โ create a tar with Bzip2
compression
tar xjf file.tar.bz2 โ extract a tar using Bzip2
gzip file โ compresses file and renames it to
file.gz
gzip -d file.gz โ decompresses file.gz back to
file
Network
ping host โ ping host and output results
whois domain โ get whois information for domain
dig domain โ get DNS information for domain
dig -x host โ reverse lookup host
wget file โ download file
wget -c file โ continue a stopped download
Installation
Install from source:
./configure
make
make install
dpkg -i pkg.deb โ install a package (Debian)
rpm -Uvh pkg.rpm โ install a package (RPM)
Shortcuts
Ctrl+C โ halts the current command
Ctrl+Z โ stops the current command, resume with
fg in the foreground or bg in the background
Ctrl+D โ log out of current session, similar to exit
Ctrl+W โ erases one word in the current line
Ctrl+U โ erases the whole line
Ctrl+R โ type to bring up a recent command
!! - repeats the last command
exit โ log out of current session
* use with extreme caution.