File Commands

System Info

ls – directory listing

date – show the current date and time

ls -al – formatted listing with hidden files

cal – show this month's calendar

cd dir - change directory to dir

uptime – show current uptime

cd – change to home

w – display who is online

pwd – show current directory

whoami – who you are logged in as

mkdir dir – create a directory dir

finger user – display information about user

rm file – delete file

uname -a – show kernel information

rm -r dir – delete directory dir

cat /proc/cpuinfo – cpu information

rm -f file – force remove file

cat /proc/meminfo – memory information

rm -rf dir – force remove directory dir *

man command – show the manual for command

cp file1 file2 – copy file1 to file2

df – show disk usage

cp -r dir1 dir2 – copy dir1 to dir2; create dir2 if it doesn't exist

du – show directory space usage

free – show memory and swap usage

mv file1 file2 – rename or move file1 to file2 if file2 is an existing directory, moves file1 into directory file2

whereis app – show possible locations of app

which app – show which app will be run by default

Compression

ln -s file link – create symbolic link link to file

touch file – create or update file

tar cf file.tar files – create a tar named file.tar containing files

cat > file – places standard input into file

more file – output the contents of file

tar xf file.tar – extract the files from file.tar

head file – output the first 10 lines of file

tar czf file.tar.gz files – create a tar with Gzip compression

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

tar xzf file.tar.gz – extract a tar using Gzip

tar cjf file.tar.bz2 – create a tar with Bzip2 compression

Process Management

tar xjf file.tar.bz2 – extract a tar using Bzip2

ps – display your currently active processes

gzip file – compresses file and renames it to file.gz

top – display all running processes

kill pid – kill process id pid

gzip -d file.gz – decompresses file.gz back to file

killall proc – kill all processes named proc *

bg – lists stopped or background jobs; resume a stopped job in the background

Network

fg – brings the most recent job to foreground

ping host – ping host and output results

fg n – brings job n to the foreground

whois domain – get whois information for domain

File Permissions

dig domain – get DNS information for domain

dig -x host – reverse lookup host

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.

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)

SSH

Shortcuts

ssh user@host – connect to host as user

ssh -p port user@host – connect to host on port port as user

Ctrl+C – halts the current command

Ctrl+Z – stops the current command, resume with fg in the foreground or bg in the background

ssh-copy-id user@host – add your key to host for user to enable a keyed or passwordless login

Ctrl+D – log out of current session, similar to exit

Ctrl+W – erases one word in the current line

Searching

Ctrl+U – erases the whole line

grep pattern files – search for pattern in files

Ctrl+R – type to bring up a recent command

grep -r pattern dir – search recursively for pattern in dir

!! - repeats the last command

exit – log out of current session

command | grep pattern – search for pattern in the output of command

* use with extreme caution.

locate file – find all instances of file