unix/linux command reference

1. FILE COMMANDS

ls - directory listing
ls – al – formatted listing with hidden files
cd dir – change to home
pwd – show current dir
rm file – delete file
rm -r dir – delete firectory dir
rm -f file – force remove file
rem -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 file1 to file2 if file2 is an existing directory, moves file1 into directory file2
ls -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 line of file
tail -f file – output the contentsof file as it grows, start with the 10 lines

2. 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

3. FILE PERMISSTION

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, rc for group and world

4. 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 you key to host for user to enable a keyed or passwordless login

5. 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 ther output of command
locate file – find all instances of file

6. 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 informagion ablut 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
du – show directory space usage
free – show memory and swap usage
whereis app – show possible locations of app
which app – show which app will be run by default

7. COMPARESSION

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 using 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

8. 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 -f file – continue a stopped download

9. INSTALLATION

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

10. 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
!! - repeates the last command
exit – log out of current session