Basic file and directory operations
Print current working directory: pwd
#pwd
Show files in current directory: ls
#ls
Show maximum information about all files, including hidden: ls -a
#ls -l
Move/rename a file or directory (be careful that you don’t move the source over a destination with the same name): mv [source] [destination]
#mv /home/file.txt /var/html
Delete target forever (be very careful), use -r recursive flag for directories: rm [target]
#rm file.txt
Copy file or directory: cp [source] [destination]
#cp /home/file.txt /var/html/
Mount filesytem(cdrom,usb): mount /dev/[device name] /media/[device name]
#mount /dev/cdrom /media/cdrom
Unmount the filesystem: umount /media/[device name]
#umount /media/cdrom
Forensically clone filesystems and do other low-level operations on files. Very dangerous:dd
#dd if=/dev/sda1 of=/dev/sdb1=/dev/sdb1 bs=64K conv=noerror, sync status=progress
Work with filesystems and partitions. (Easier, still quite dangerous): fdisk
#fdisk
System Administration
Execute Linux commands as an administrator (dangerous, but necessary for system administration tasks): sudo [command]
#sudo apt-get install nmap
Become system administrator: sudo -s
#sudo -s
Quit system administration(Exit root): exit
#exit
Check distro repositories for software updates(Debian based system):sudo apt-get update
#sudo apt-get update
Download and install updates (update first): sudo apt-get upgrade
#sudo apt-get upgrade
Search for package in the repositories: apt-cache search [keyword]
#apt-cache search nmap
Get more detail on one specific package: apt-cache show [package name]
#apt-cache show nmap
Download and install a package: sudo apt-get install [package name]
#sudo apt-get install nmap
View the output of a command in a more convenient format: [command] | less
# cat /var/log/messages | less
Install a .deb file from command line: sudo dpkg -i package.deb
#sudo dpkg -i nmap.deb
Working with files
Print contents of file in terminal: cat [file]
#cat /etc/apt/sources.list
Find files matching [filename]: locate [filename]
#locate httpd.conf
Search through [filename] for matches to [phrase]: grep [phrase] [filename]
#grep server httpd.conf
Search through output of a command for [phrase]: [command] | grep [phrase]
#lspci | grep VGA
View the differences between two files: diff [file 1] [file 2]
#diff /etc/apt/sources.list /etc/apt/sources.list.bkup
Output the top -n lines of [file]: head -n [number of lines] [file]
#head -n 6 /etc/apt/sources.list
Like head, but it outputs the last -n lines: tail
#tail -n 6 /etc/apt/sources.list
Checksum a file: md5sum [file]
#md5sum package.iso
Checksum every file in a directory: md5deep [directory]
#md5deep /home
Call [command] every -n seconds, and display output: watch -n [number of seconds] [command]
#watch -n 20 lsusb
Execute [command], print how long it took: time [command]
#time lsusb
Remove spaces from filenames in current directory: rename -n ‘s/[\s]/”/g’ *
#rename -n 's/[\s]/''/g' *
change capitals to lowercase in filenames in current directory: rename ‘y/A-Z/a-z/’ *
#rename 'y/A-Z/a-z/' *
Working With Processes:
List all running processes: ps -e
#ps -e
Standard system monitor showing a more extensive view of all processes and system resources: top
#top
Like top, but with a better, cleaner interface: htop
#htop
Stop a process from using all system resources and lagging computer: nice [process name]
#nice httpd
Kill misbehaving process (use sparingly, last resort, try ‘nice’ command first): pkill [process name]
pkill httpd
Compression and Encryption:
Make a simple compressed backup of a file or directory: tar -cvzf [backup output.tgz] [target file or directory]
#tar -cvzf etc.tgz /etc
Encrypt a file: gpg -o [outputfilename.gpg] -c [target file]
#gpg -o outputfilename.gpg -c targetfile
Decrypt a file: gpg -o [outputfilename] -d [target.gpg]
#gpg -o outputfilename -d target.gpg
Zip and encrypt a directory simultaneously: gpg-zip -o encrypted-filename.tgz.gpg -c -s file-to-be-encrypted
#gpg-zip -o encrypted-filename.tgz.gpg -c -s file-to-be-encrypted
gpg-zip -o encrypted-filename.tgz.gpg -c -s file-to-be-encrypted
The BASH SHELL
File Name expansions:
Current user’s home directory: ~/
~/
Current directory: ./
./
Parent directory: ../
Or even (Two parent directories down): ../../
../../
All files in target directory. (Be very careful.): /*
Output Redirects:
Redirect output of one command into the input of another with a pipe: [command 1] | [command 2]
#ps -aux | grep "mysqld"
Or even: [command 1] | [command 2] | [command 3]
Redirect output to a file: [command] > file or [file] > [file]
# ps > file.txt
Or even, to redirect in a different direction: [file] < [file]
#/etc/apt/sources.list < /etc/apt/sources.list
Append output rather than writing over the target file: [file/command] >> [file]
#echo "new line of text" >> /etc/apt/sources.list
Controlling Execution
Wait until [command 1] is finished to execute [command 2]: [command 1] ; [command 2]
#wget https://wordpress.org/latest.zip; ls;
or evcen: [command 1] ; [command 2]:[command 3] ;
Users and Groups
Change owner of a file or directory: chown
#chown mydir
Change privileges over file or directory: chmod
#chmod 755 /var/www/html
Create a new user: adduser
#adduser john
Change user privileges (be very careful with this one): usermod
#usermod [options] username
Delete user: deluser
#deluser john
Delete user: groups
Create a new group: groupadd
#groupadd groupname
Change group privileges: groupmod
#groupmod [options] groupname
Print usernames of logged in users: users
#users
Environment and Hardware
Print full date and time: date
#date
Print the hostname of this machine: echo $HOSTNAME
#echo $HOSTNAME
Print information about current linux distro: lsb_release -a
#lsb_release -a
Print linux kernel version: uname -a
#uname -a
Print information about kernel modules: lsmod
#lsmod
Configure kernel modules (never do this): modprobe
#modprobe
View Installed packages(debain based system): dpkg –get-selections
#dpkg --get-selections
Print environment variables: printenv
#printenv
List hardware connected via PCI ports: lspci
#lspci
List hardware connected via USB ports: lsusb
#lsusb
Print hardware info stored in BIOS: sudo dmidecode
#sudo dmidecode
Dump captured data off of wireless card: dumpcap
#dumpcap
Dump info about keyboard drivers: dumpkeys
#dumpkeys
Tags:
LINUX