Linux Commands(Continues)

Linux Commands

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 login

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

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
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 in Linux

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

* use with extreme caution.

Linux Commands

Linux Commands

File Commands

ls – directory listing

ls -al – formatted listing with hidden files

cd dir - change directory to dir

cd – change to home

pwd – show current directory

mkdir dir – create a 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 or move file1 to file2

if file2 is an existing directory, moves file1 into

directory 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.