Linux system provides Linux commands are run in the terminal used to do all tasks of Administration.Different types of commands are
System commands, Hardware commands, Users commands, File Commands, Process Related commands, File Permission commands, Network commands, Compression/Archives commands, Install Packages commands, Install Source (Compilation) commands, Search commands, Login commands, File Transfer commands, Disk Usage commands, Directory Traverse commands.
1. System
| S. No |
Command |
Details |
|
1
|
uname
|
DisplaysLinux system information
|
|
2
|
uname -r
|
Displays kernel release information
|
|
3
|
uptime
|
Displays how long the system has been running including load average
|
|
4
|
hostname
|
Shows the system hostname
|
|
5
|
hostname -i
|
Displays the IP address of the system
|
|
6
|
last reboot
|
Shows system reboot history
|
|
7
|
date
|
Displays current system date and time
|
|
8
|
timedatectl
|
Query and change the System clock
|
|
9
|
cal
|
Displays the current calendar month and day
|
|
10
|
w
|
Displays currently logged in users in the system
|
|
11
|
whoami
|
Displays who you are logged in as
|
|
12
|
finger username
|
Displays information about the user
|
2. Hardware
| S. No |
Command |
Details |
|
1
|
dmesg
|
Displays bootup messages
|
|
2
|
cat /proc/cpuinfo
|
Displays more information about CPU e.g model, model name, cores, vendor
id
|
|
3
|
cat /proc/meminfo
|
Displays more information about hardware memory e.g. Total and Free memory
|
|
4
|
lshw
|
Displays information about system's hardware configuration
|
|
5
|
lsblk
|
Displays block devices related information
|
|
6
|
free -m
|
Displays free and used memory in the system (-m flag indicates memory in
MB)
|
|
7
|
lspci -tv
|
Displays PCI devices in a tree-likediagram
|
|
8
|
lsusb-tv
|
Displays USB devices in a tree-like diagram
|
|
9
|
dmidecode
|
Displays hardware information from the BIOS
|
|
10
|
hdparm-i /dev/xda
|
Displays information about disk data
|
|
11
|
hdparm-tT /dev/xda<:code>
|
Conducts a read speed test on device xda
|
|
12
|
badblocks-s /dev/xda
|
Tests for unreadable blocks on disk
|
3. Users
| S. No |
Command |
Details |
|
1
|
id
|
Displays the details of the active user e.g. uid, gid, and groups
|
|
2
|
last
|
Shows the last logins in the system
|
|
3
|
who
|
Shows who is logged in to the system
|
|
4
|
groupadd "admin"
|
Adds the group 'admin'
|
|
5
|
adduser "Sam"
|
Adds user Sam
|
|
6
|
userdel "Sam"
|
Deletes user Sam
|
|
7
|
usermod
|
Used for changing / modifying user information
|
4. File Commands
| S. No |
Command |
Details |
|
1
|
ls –al
|
Lists files - both regular &hidden files and their permissions as well.
|
|
2
|
pwd
|
Displays the current directory file path
|
|
3
|
mkdir 'directory_name'
|
Creates a new directory
|
|
4
|
rm file_name
|
Removes a file
|
|
5
|
rm -f filename
|
Forcefully removes a file
|
|
6
|
rm -r directory_name
|
Removes a directory recursively
|
|
7
|
rm -rf directory_name
|
Removes a directory forcefully and recursively
|
|
8
|
cp file1 file2
|
Copies the contents of file1 to file2
|
|
9
|
cp -r dir1 dir2
|
Recursively Copies dir1 to dir2. dir2 is created if it does not exist
|
|
10
|
mv file1 file2
|
Renames file1 to file2
|
|
11
|
ln -s /path/to/file_name link_name
|
Creates a symbolic link to file_name
|
|
12
|
touch file_name
|
Creates a new file
|
|
13
|
cat > file_name
|
Places standard input into a file
|
|
14
|
more file_name
|
Outputs the contents of a file
|
|
15
|
head file_name
|
Displays the first 10 lines of a file
|
|
16
|
tail file_name
|
Displays the last 10 lines of a file
|
|
17
|
gpg -c file_name
|
Encrypts a file
|
|
18
|
gpg file_name.gpg
|
Decrypts a file
|
|
19
|
wc
|
Prints the number of bytes, words and lines in a file
|
|
20
|
xargs
|
Executes commands from standard input
|
5. Process Related
| S. No |
Command |
Details |
|
1
|
ps
|
Display currently active processes
|
|
2
|
ps aux | grep 'telnet'
|
Searches for the id of the process 'telnet'
|
|
3
|
pmap
|
Displays memory map of processes
|
|
4
|
top
|
Displays all running processes
|
|
5
|
kill pid
|
Terminates process with a given pid
|
|
6
|
killall proc
|
Kills / Terminates all processes named proc
|
|
7
|
pkill process-name
|
Sendsa signal to a process with its name
|
|
8
|
bg
|
Resumes suspended jobs in the background
|
|
9
|
fg
|
Brings suspended jobs to the foreground
|
|
10
|
fg n
|
job n to the foreground
|
|
11
|
lsof
|
Lists files that are open by processes
|
|
12
|
renice 19 PID
|
makes a process run with very low priority
|
|
13
|
pgrep firefox
|
find Firefox process ID
|
|
14
|
pstree
|
visualizing processes in tree model
|
6. File Permission
| S. No |
Command |
Details |
|
1
|
chmod octal filename
|
Change file permissions of the file to octal
|
|
2
|
Example
|
|
|
3
|
chmod 777 /data/test.c
|
Set rwx permissions to owner, group and everyone (everyone else who has
access to the server)
|
|
4
|
chmod 755 /data/test.c
|
Set rwx to the owner and r_x to group and everyone
|
|
5
|
chmod766 /data/test.c
|
Sets rwx for owner, rw for group and everyone
|
|
6
|
chown owner user-file
|
Change ownership of the file
|
|
7
|
chownowner-user:owner-group file_name
|
Change owner and group owner of the file
|
|
8
|
chown owner-user:owner-group directory
|
Change owner and group owner of the directory
|
7. Network
| S. No |
Command |
Details |
|
1
|
ifconfig
|
Displays IP addresses of all network interfaces
|
|
2
|
netstat -pnltu
|
Displays all active listening ports
|
|
3
|
ping host
|
ping command sends an ICMP echo request to establish a connection to
server / PC
|
|
4
|
arp
|
Address Resolution Protocol (arp)
used to finding an address of a computer in a network
|
|
5
|
telnet
|
Used to communicate with other computer
|
|
6
|
ftp
|
Used to transfer file. To remote system.
ftp 10.2.0.7
Enter : user name,password
put a.txt
bye
|
|
7
|
Finger
|
Used check the information of any user from remote or local command line
interface.
|
|
8
|
ip address add 192.168.0.1/24 dev eth0
|
Assigns IP address 192.168.0.1 to interface eth0
|
|
9
|
ip addr show
|
Displays IP addresses and all the network interfaces
|
|
10
|
whois domain
|
Retrieves more information about a domain name
|
|
11 |
dig domain
|
Retrieves DNS information about the domain
|
|
12
|
dig -x host
|
Performs reverse lookup on a domain
|
|
13 |
host google.com
|
Performs an IP lookup for the domain name
|
|
14
|
hostname -i
|
Displays local IP address
|
|
15
|
wget file_name
|
Downloads a file from an online source
|
8. Compression/Archives
| S. No |
Command |
Details |
|
1
|
tar -cf home.tar home<:code>
|
Creates archive file called 'home.tar' from file 'home'
|
|
2
|
tar -xf files.tar
|
Extract archive file 'files.tar'
|
|
3
|
tar -zcvf home.tar.gz source-folder
|
Creates gzipped tar archive file from the source folder
|
|
4
|
gzip file
|
Compression a file with .gz extension
|
9. Install Packages
| S. No |
Command |
Details |
|
1
|
rpm -i pkg_name.rpm
|
Install an rpm package
|
|
2
|
rpm -e pkg_name
|
Removes an rpm package
|
|
3
|
dnf install pkg_name
|
Install package using dnf utility
|
10. Install Source (Compilation)
| S. No |
Command |
Details |
|
1
|
./configure
|
Checks your system for the required software needed to build the program.
It will build the Makefile containing the instructions required to effectively
build the project
|
|
2
|
make
|
It reads the Makefile to compile the program with the required operations.
The process may take some time, depending on your system and the size of the
program
|
|
3
|
make install
|
The command installs the binaries in the default/modified paths after the
compilation
|
11. Search
| S. No |
Command |
Details |
|
1
|
grep 'pattern' files
|
Search for a given pattern in files
|
|
2
|
grep -r pattern dir
|
Search recursively for a pattern in a given directory
|
|
3
|
locate file
|
Find all instances of the file
|
|
4
|
find /home/ -name "index"
|
Find file names that begin with 'index' in /home folder
|
|
5
|
find /home -size +10000k
|
Find files greater than 10000k in the home folder
|
12. Login
| S. No |
Command |
Details |
|
1
|
sshuser@host
|
Securely connect to host as user
|
|
2
|
ssh -p port_numberuser@host
|
Securely connect to host using a specified port
|
|
3
|
ssh host
|
Securely connect to the system via SSH default port 22
|
|
4
|
telnet host
|
Connect to host via telnet default port 23
|
13. File Transfer
| S. No |
Command |
Details |
|
1
|
scp file1.txt server2/tmp
|
Securely copy file1.txt to server2 in /tmp directory
|
|
2
|
rsync -a /home/apps /backup/
|
Synchronize contents in /home/apps directory with /backup directory
|
14. Disk Usage
| S. No |
Command |
Details |
|
1
|
df -h
|
Displays free space on mounted systems
|
|
2
|
df -i
|
Displays free inodes on filesystems
|
|
3
|
fdisk -l
|
Shows disk partitions, sizes, and types
|
|
4
|
du -sh
|
Displays disk usage in the current directory in a human-readable format
|
|
5
|
findmnt
< |
Displays target mount point for all filesystems
|
|
6
|
mount device-path mount-point
|
Mount a device
|
15. Directory Traverse
| S. No |
Command |
Details |
|
1
|
cd ..
|
Move up one level in the directory tree structure
|
|
2
|
cd
|
Change directory to $HOME directory
|
|
3
|
cd /test
|
Change directory to /test directory
|
inode= data structure on a filesystem onLinux( stores = name + actual data).
|