12 min to read
Linux Cheat Sheet 101
Linux,where a true freedom is !
Linux is a kernel, on which lots of Operating systems like andriod, Debian, Arch are runnig.
The Linux “core” (called a kernel) was born in 1991 in Finland, and it has come a really long way from its humble beginnings. It went on to be the kernel of the GNU Operating System, creating the duo GNU/Linux.
What makes Linux special is,Distro !
Eg of linux distro are:-Ubuntu, Debian, kali, Parrot,openSUSE,Fedora
System
| Commands | Descriptions |
|---|---|
| uname | Display the Linux information |
| uname-r | Display the kernel information |
| utime | Display how long the system has been running including the load average |
| hostname | shows the system hostname |
| hostname-i | display the IP address of the system |
| last reboot | shows the system reboot history |
| date | Display the current system date & time |
| timedatectl | Query and change the system clock |
| cal | Display the current calendar month and day |
| w | Display currently logged in users in the system |
| whoami | Display who you are logged in |
| finger username | Display the information about the user |
Hardware
| Commands | Descriptions |
|---|---|
| dmseg | Display bootup messages |
| cat/proc/cpuinfo | Displays more information about CPU eg. model, model name,cores,vendor id |
| cat/proc/meminfo | Display the more information about hardware memory e.g total and free memory |
| lshw | Display information about system's hardware configuration |
| lsblk | Display the block device related information |
| free -m | Display free and used memory in the system (-m flag indicates memory in MB ) |
| lspci -tv | Display PCI devices in a tree-like diagram |
| lsusb -tv | Display USB devices in a tree-like diagram |
| dmidecode | Display hardware information from the BIOS |
| hdparm -i /dev/xda | Display information about the disk data |
| hdparm -tT/dev/xda | Conducts a read speed test on device xda |
| badblocks -s/dev/xda | Test for unreadable blocks on disk |
User
| Commands | Descriptions |
|---|---|
| id | Displays the details of the active user e.g uid,gid, and groups |
| Last | Shows the last logins in the System |
| who | Shows who is logged into the System |
| groupadd "admin" | Adds the group "admin" |
| adduser"Shubham" | Adds user Shubham |
| userdel"Sam" | Deletes user Sam |
| usermod | used for changing/modifying user information |
File commands
| Commands | Descriptions |
|---|---|
| ls -al | List files both regular and hidden along with their permission |
| pwd | Display the path of the current directory |
| mkdir <directory_name> | Creates a directory |
| rm <file_name> | Delete file |
| rm -r <directory_name> | Delete directory recursively |
| rm -f <file_name> | Forcefully remove file |
| rm -rf <directory_name> | Forcefully remove the directory |
| cp file1 file2 | copy file1 to file2 |
| cp -r dir1 dir2 | copy dir1 to dir2 ,creates dir2 if it doesn't exits |
| mv file1 file2 | Rename source to Destination/move source to directory |
| ln -s /path/to/file-name link name | Creates symbolic link to the file-name |
| touch file | Creates/ Update file |
| cat > file | Place standard input into filel |
| more file | Output contents of file |
| head file | Output first 10 lines of file |
| tail file | Output last 10 lines of file |
| tail -f file | Output contents of file as it grows starting with the last 10 lines |
| gpg -c file | Encrypt file |
| gpg file.gpg | Decrypt file |
| wc | print the number of bytes,words,and lines in files |
| xargs | Execute command lines from standard input |
File Permission Related
| Commands | Descriptions |
|---|---|
| chmod octal < file_name> | Change the permission of the file to local |
| Eg: - | |
| chmod 777 /data/test.c | Set rwx permission for owner,group,world |
| chmod 755/data/test.c | Set rws permission for the owner, rx for group and world |
| chmod 766/data/test.c | Sets rwx for the owner,rw for the group and everyone |
| chown owner user-file | Changes the ownership of the file |
| chown owner-user:owner-group < file_name> |
change owner and group owner of the file |
| chown owner-user:owner-group -directory |
change owner and group owner of the directory |
Process Related
| Commands | Descriptions |
|---|---|
| ps | Display the current active processes |
| ps aux | grep 'telnet' | Searches for the id of the process 'telnet' |
| pmap | Display memory map of the process |
| top | Displays all running processes |
| kill pid | Terminates process with a given pid |
| killall proc | kills/Terminates all processes named proc |
| pkill process-name | Sends a signal to a process with its a name |
| bg | Resume suspended jobs in the background |
| fg | Brings suspended jobs to the foreground |
| fg n | Brings job n to the foreground |
| lsof | Lists files that are open by processes |
| renic 19 PID | Makes a process run with very low priority |
| pregp firefox | find Firefox process ID |
| pstree | Visualizing processess in tree model |
Network Related
| Commands | Descriptions |
|---|---|
| ip addr show | Displays IP addresses and all the network interfaces |
| ip address add 192.1.20 dev eth0 |
Set Ip address |
| ifconfig | Displays Ip addresses of all network interfaces |
| ping host | ping command sends an ICMP echo request to establish a connection to server/Pc |
| whois domain | Retrievs more information about a domain name |
| dig domain | Retrievs DNS infromation about the domain |
| dig-x host | Performs reverse lookup on a domain |
| host google.com | perfroms an Ip lookup for the domain name |
| hostname-i | Display all local Ip address |
| wget <file_name> | Downloads a file from an online source |
| netstat-pnltu | Displays all active listening port |
Compression/Archives
| Commands | Descriptions |
|---|---|
| tar -cf home.tar home | creates archive file called 'home.tar' from file 'home' |
| tar -Xf files.tar | Extracct archive file 'files.tar' |
| tar -ZCVf home.tar.gz Source-folder |
Creates gzipped tar archive file from source folder |
| gzip file | Compression a file with .gz extension |
Install packages
| Commands | Descriptions |
|---|---|
| rpm -i pkg_name.rpm | Install an rpm package |
| rpm -e pkg_name | Removes an rpm package |
| dnf install pkg_name | Install package using dnf utility |
Install Source (Compilation)
./ configure
make
make install
Search
| Commands | Descriptions |
|---|---|
| grep 'pattern' files | Search for a given pattern in files |
| grep -r pattern dir | Search recursively for a pattern in a given directory |
| locate file | Find all instances of the file |
| find /home/ -name "index" | Find file names that begin with 'index in /home folder |
| find /home/ -size +10000k | Find files greater than 10000k in the home folder |
Login
| Commands | Descriptions |
|---|---|
| ssh user@host | Securely connect to host as user |
| ssh -p <port_number> user@host |
Securely connect to host using a specified port |
| ssh host | Securely connect to the system via SSH default port 22 |
| telnet host | Connect to host via telnet default port 23 |
File Transfer
| Commands | Descriptions |
|---|---|
| scp file1.txt server2/tmp | Securely copy file1.txt to server2 in /tmp diretory |
| rsync -a/home/apps /backup | Synchronize contents in /home/apps directory with directory |
Disk usages
| Commands | Descriptions |
|---|---|
| df -h | Displays free space on mounted systems |
| df -i | Displays free inodes on filesystems |
| fdisk -l | Shows disk partitions, sizes,and types |
| du -sh | Displays disk usage in the current directory in a human readable format |
| findmnt | Displays target mount points for all filesystems |
| mount device-path mount-point |
Mount a device |
Directory Traverse
| Commands | Descriptions |
|---|---|
| cd .. | Move up one level in the directory tree structure |
| cd | change directory to the $HOME directory |
| cd /test | Change directory to the /test directory |
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