Complete Unix Commands And Basic Linux Commands With Examples For Beginners

To learn something we should start from the basics. In this article, we are going to learn the most and useful basic Linux commands or Unix commands. I would suggest you should read this article if you are going to start learning Linux or interested in Linux. This article will give approximately all the basic Linux commands which will make Linux easier to understand. Not only basic you will get much more than that, but I mean to say this article is useful also for experienced Linux admins.

Complete Unix Commands And Basic Linux Commands With Examples For Beginners

Complete Unix Commands And Basic Linux Commands With Examples For Beginners

So Let’s have a look at the below Linux commands or Unix commands.

1. Operating System Related Linux Commands

If someone asks which operating system you are currently using or proves that you are using a Linux Operating System then you can use uname command to prove the same.

[root@localhost ~]# uname  # To check the Current Operating System 
Linux

uname command with option -a will give you some more useful information like Computer Name, Kernel Version, Operating System architecture, etc.

[root@localhost ~]# uname -a   # To check Linux Kernel Verison and OS details
Linux localhost.localdomain 3.10.0-514.el7.x86_64 #1 SMP Sat Aug 22 16:42:41 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

2. List files and directories we can use ls command.

ls Linux Commands are used to list files and directories in Linux.

[root@localhost ~]# ls   # List Files and Directories
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates
Desktop          Downloads  Music                 Public    Videos

ls with option -l will give some more details about files and directories like Permissions, Owner of the files and dir’s, created and modifies date and time, etc.

[root@localhost ~]# ls -l   # List Files and Directories with more Advance Information
total 8
-rw-------. 1 root root 1530 Feb  2 17:39 anaconda-ks.cfg
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Desktop
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Documents
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Downloads
-rw-r--r--. 1 root root 1578 Feb  2 21:56 initial-setup-ks.cfg
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Music
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Pictures
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Public
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Templates
drwxr-xr-x. 2 root root    6 Feb  2 22:05 Videos

To check the Hidden files and directories you can use ls command with option -a

[root@localhost ~]# ls -a   # To check hidden Files and Directories
.                .bash_profile  .dbus      .ICEauthority         Public
..               .bashrc        Desktop    initial-setup-ks.cfg  .tcshrc
anaconda-ks.cfg  .cache         Documents  .local                Templates
.bash_history    .config        Downloads  Music                 Videos
.bash_logout     .cshrc         .esd_auth  Pictures

Also Read – How to Increase Existing Software Raid 5 Storage Capacity In Linux

3. Directory Related Linux Commands

Directory Related Linux commands are like create, delete, change directories, etc.

To create a directory in Linux you can use mkdir (Referred as Make Directory) command and Remove/Delete a directory use rmdir (Referred as Remove Directory). To go into the directory use cd (Referred as Change Directory) command. To check you are currently in which directory or current directory path we can use the pwd command. Refer to the output below for directory related Linux commands.

[root@localhost ~]# mkdir test   # Create a Directory
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  Videos
Desktop          Downloads  Music                 Public    test
[root@localhost ~]# rmdir test   # Delete a Directory
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates
Desktop          Downloads  Music                 Public    Videos
[root@localhost ~]# mkdir test
[root@localhost ~]# cd test/   # Change Directory
[root@localhost test]# pwd
/root/test
[root@localhost test]# cd ..
[root@localhost ~]# pwd   # Check the current Path
/root
[root@localhost ~]# 

4. Files Operation Linux Commands

File operation Linux commands are used to create, delete, list, display and edit the files.

To create a file we can use the touch command, Follow the output below.

[root@localhost ~]# touch test.txt   # Create a File
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  test.txt
Desktop          Downloads  Music                 Public    test       Videos
[root@localhost ~]# touch test/test.txt  # Create a File under Directory
[root@localhost ~]# ls test
test.txt

One more useful command is there in Linux is a cat, We can use the cat command to create a new file and also to display the content of the file. Follow the output for cat Linux commands.

[root@localhost ~]# cat > test.txt   # Create a File using cat
Welcome to itsmarttricks.com
[root@localhost ~]# cat test.txt    # Display the content of the file
Welcome to itsmarttricks.com
[root@localhost ~]# cat >> test.txt    # Append/edit a File
Here you can get quality Linux Tutorials
[root@localhost ~]# cat test.txt  # Confirm the edited text
Welcome to itsmarttricks.com
Here you can get quality Linux Tutorials

less Linux commands help us to display long files in a scrolling way. you can use up and down the error to forward and backward the file I mean to say scroll the file.

[root@localhost ~]# less /etc/passwd   # Display file using less command
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
systemd-bus-proxy:x:999:998:systemd Bus Proxy:/:/sbin/nologin
systemd-network:x:192:192:systemd Network Management:/:/sbin/nologin
dbus:x:81:81:System message bus:/:/sbin/nologin
polkitd:x:998:997:User for polkitd:/:/sbin/nologin
abrt:x:173:173::/etc/abrt:/sbin/nologin
unbound:x:997:996:Unbound DNS resolver:/etc/unbound:/sbin/nologin
tss:x:59:59:Account used by the trousers package to sandbox the tcsd daemon:/dev/null:/sbin/nologin
libstoragemgmt:x:996:995:daemon account for libstoragemgmt:/var/run/lsm:/sbin/nologin
rpc:x:32:32:Rpcbind Daemon:/var/lib/rpcbind:/sbin/nologin
colord:x:995:994:User for colord:/var/lib/colord:/sbin/nologin
usbmuxd:x:113:113:usbmuxd user:/:/sbin/nologin
/etc/passwd

We can see the content of the file using head command. the head command will display first 10 Lines of the file.

[root@localhost ~]# head /etc/passwd   # Display file using head command
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
operator:x:11:0:operator:/root:/sbin/nologin

Also Read – How To Create Symlink (Symbolic Link) And Hardlink In Linux

Like head command, We can see the content of the file using the tail command. the tail command will display the last 10 Lines of the file.

[root@localhost ~]# tail /etc/passwd   # Display file using tail Command
setroubleshoot:x:991:988::/var/lib/setroubleshoot:/sbin/nologin
pulse:x:171:171:PulseAudio System Daemon:/var/run/pulse:/sbin/nologin
gdm:x:42:42::/var/lib/gdm:/sbin/nologin
gnome-initial-setup:x:990:985::/run/gnome-initial-setup/:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
avahi:x:70:70:Avahi mDNS/DNS-SD Stack:/var/run/avahi-daemon:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
tcpdump:x:72:72::/:/sbin/nologin
itsmarttricks:x:1000:1000:itsmarttricks:/home/itsmarttricks:/bin/bash

To check the manual page or help page of any command we can use man command.

[root@localhost ~]# man ls   # check command help page
LS(1)                               User Commands                              LS(1)

NAME
       ls - list directory contents

SYNOPSIS
       ls [OPTION]... [FILE]...

DESCRIPTION
       List  information  about  the FILEs (the current directory by default).  Sort
       entries alphabetically if none of -cftuvSUX nor --sort is specified.

       Mandatory arguments to long options are mandatory for short options too.

       -a, --all
              do not ignore entries starting with .

       -A, --almost-all
              do not list implied . and ..

       --author
              with -l, print the author of each file

To check the already executed command use the history command.

[root@localhost ~]# history   # Checking Already executed Commands
    1  clear
    2  fdisk -l
    3  ifconfig 
    4  fdisk -l
    5  init 0
    6  uname
    7  uname -a
    8  ls
    9  ls -l
   10  ls -a

locate command is used to find the path of any file.

[root@localhost ~]# locate chmod   # Find the File Path using locate command
/usr/bin/chmod
/usr/share/man/man1/chmod.1.gz
/usr/share/man/man1p/chmod.1p.gz
/usr/share/man/man2/chmod.2.gz
/usr/share/man/man2/fchmod.2.gz
/usr/share/man/man2/fchmodat.2.gz
/usr/share/man/man3p/chmod.3p.gz
/usr/share/man/man3p/fchmod.3p.gz

To check the date, time, month, and year of the Linux system use the date command.

[root@localhost ~]# date   # Check Date and Time
Sat Aug 24 02:40:58 IST 2019

To close the current terminal you can use the exit command.

exit   # Exit a Terminal

To clear the terminal screen using the clear command.

clear   # Clear the Terminal Screen

To run any command as root we can use the Sudo command. For example, you are logged in as a normal user,  and you want to install some package. In that case, you have installed it using the Sudo command.

sudo yum -y install vsftpd   # Run a Command as root using sudo

vi command is used as a text editor in Linux Systems.

[root@localhost ~]# vi /etc/httpd/conf/httpd.conf   # Edit a file using vi

Also, you can use the nano command as an editor in Linux.

[root@localhost ~]# nano /etc/httpd/conf/httpd.conf    # Edit a File using nano

grep command is used as a search command in Linux. For example, here I am searching for word itsmarttricks in file /etc/passwd.

[root@localhost ~]# cat /etc/passwd | grep itsmarttricks   # Search for Word
itsmarttricks:x:500:500:itsmarttricks:/home/itsmarttricks:/bin/bash

grep command with option -i will allow searching case insensitive words.

[root@localhost data]# cat file1.txt | grep -i mangesh   # Search case insensitive Word
MangeshDhulap

Network Related Basic Linux Commands

To check the IP Address in the Linux system we can use the command ifconfig. This will list all connected NIC (Network Interface Card) OR LAN Card with loopback LAN.

[root@localhost ~]# ifconfig    # Check IP Address
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.100  netmask 255.255.255.0  broadcast 192.168.1.1
        ether 00:0c:29:36:fd:a7  txqueuelen 1000  (Ethernet)
        RX packets 511  bytes 31797 (31.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10
        loop  txqueuelen 1  (Local Loopback)
        RX packets 388  bytes 33748 (32.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 388  bytes 33748 (32.9 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

virbr0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 192.168.122.1  netmask 255.255.255.0  broadcast 192.168.122.255
        ether 52:54:00:7d:e7:fe  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

To check the IP Address of a particular NIC execute the command ifconfig <NIC Name>. Refer to the sample output below.

[root@localhost ~]# ifconfig ens33   # Check IP Address of a Particular LAN
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        ether 00:0c:29:36:fd:a7  txqueuelen 1000  (Ethernet)
        RX packets 559  bytes 34677 (33.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

To check the hostname of the Linux system uses the below command.

[root@localhost ~]# nano /etc/hostname   # Check Hostname

itsmarttricks

# OR you can use just hostname command to check the Hostname of the system.
[root@localhost ~]# hostname
itsmarttricks

Also Read – TAR Command Examples in Linux

To set IP Address OR configure the NIC follow the below steps.

[root@localhost ~]# nano /etc/sysconfig/network-scripts/ifcfg-ens33   # Configure IP Address

TYPE=Ethernet
BOOTPROTO=none
IPADDR=192.168.1.100   # IP Address
NETMASK=255.255.255.0  # Subnet Mask
GATEWAY=192.168.1.1    # Gateway
DOMAIN="itsmarttricks.com"   # Domain
DNS1=192.168.1.100   # DNS1 IP ADDRESS
DNS2=192.168.1.101   # DNS2 IP ADDRESS
DEFROUTE=yes
PEERDNS=yes
PEERROUTES=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=ens33
UUID=fbaafa25-25cd-461d-af14-c436b35c5d7e


BOOTPROTO=dhcp

To Enable and Disable the NIC use ifup and ifdown command. Refer to the sample output below.

[root@localhost ~]# ifdown ens33   # Disable a LAN Device
Device 'ens33' successfully disconnected.

[root@localhost ~]# ifup ens33   # Enable a LAN Device
Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/2)

To check the network connectivity we can use the command ping. For example, if some website is not working then to diagnose the issue your first step would be to ping to that website. Follow the output below.

[root@localhost ~]# ping itsmarttricks.com   # Check Network Connivicity using ping
PING itsmarttricks.com (111.118.215.222) 56(84) bytes of data.
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=1 ttl=58 time=8.19 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=2 ttl=58 time=7.68 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=3 ttl=58 time=7.47 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=4 ttl=58 time=8.04 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=5 ttl=58 time=8.74 ms

ping with option -c will ping three times to a particular website.

[root@localhost ~]# ping -c 3 itsmarttricks.com   # ping 3 times
PING itsmarttricks.com (111.118.215.222) 56(84) bytes of data.
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=1 ttl=58 time=7.84 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=2 ttl=58 time=7.88 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=3 ttl=58 time=7.65 ms

--- itsmarttricks.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2011ms
rtt min/avg/max/mdev = 7.657/7.794/7.880/0.097 ms

ping with option -i will take an interval between two pings. Refer to the below output where we have three pings which took 3 seconds between each ping.

[root@localhost ~]# ping -c 3 -i 3 itsmarttricks.com  # ping 3 time with 3 seconds of interval between each ping
PING itsmarttricks.com (111.118.215.222) 56(84) bytes of data.
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=1 ttl=58 time=6.22 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=2 ttl=58 time=7.90 ms
64 bytes from cp-in-9.webhostbox.net (111.118.215.222): icmp_seq=3 ttl=58 time=7.76 ms

--- itsmarttricks.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 6016ms
rtt min/avg/max/mdev = 6.224/7.297/7.907/0.767 ms

To monitor inbound and outbound networks there is a nice tool available in Linux is netstat.

[root@localhost ~]# netstat   # Monitor Network using netstat

To list all TCP and UDP connections we can use the netstat command with option -a.

[root@localhost ~]# netstat -a

There is more network-related Linux commands are available for troubleshooting but will write a separate post for that.

System Utility Related Linux Commands

To Halt OR Shutdown the Linux system we can use the init command with run level 0, Refer to the command below.

init 0  # Shutdown the System

To restart the Linux system use command init with run level 6 OR you can use the reboot command to do the same.

init 6   # Restart the System

reboot

To check the Process Status we can use the command ps.

[root@localhost ~]# ps   # Check Processing Status
   PID TTY          TIME CMD
  3219 pts/0    00:00:00 bash
  3488 pts/0    00:00:00 cat
  3559 pts/0    00:00:00 cat
  4582 pts/0    00:00:00 ps

ps command with option -e and -f will display some more advanced reports the process used by the user i.e. UID, Process ID i.e. PID, Parent Process ID i.e PPID, Time, Command i.e. CMD, etc.

[root@localhost ~]# ps -ef

# To check the Processing Status completely page by page you can use below command.

[root@localhost ~]# ps -ef | more
UID         PID   PPID  C STIME TTY          TIME CMD
root          1      0  0 09:35 ?        00:00:02 /usr/lib/systemd/systemd --switched-r
oot --system --deserialize 21
root          2      0  0 09:35 ?        00:00:00 [kthreadd]
root          3      2  0 09:35 ?        00:00:00 [ksoftirqd/0]
root          7      2  0 09:35 ?        00:00:00 [migration/0]
root          8      2  0 09:35 ?        00:00:00 [rcu_bh]
root          9      2  0 09:35 ?        00:00:00 [rcu_sched]
root         10      2  0 09:35 ?        00:00:00 [watchdog/0]
root         12      2  0 09:35 ?        00:00:00 [khelper]
root         13      2  0 09:35 ?        00:00:00 [kdevtmpfs]
root         14      2  0 09:35 ?        00:00:00 [netns]
root         15      2  0 09:35 ?        00:00:00 [khungtaskd]
root         16      2  0 09:35 ?        00:00:00 [writeback]
root         17      2  0 09:35 ?        00:00:00 [kintegrityd]
root         18      2  0 09:35 ?        00:00:00 [bioset]
root         19      2  0 09:35 ?        00:00:00 [kblockd]
root         20      2  0 09:35 ?        00:00:00 [md]
root         26      2  0 09:35 ?        00:00:00 [kswapd0]
root         27      2  0 09:35 ?        00:00:00 [ksmd]
root         28      2  0 09:35 ?        00:00:00 [khugepaged]
root         29      2  0 09:35 ?        00:00:00 [fsnotify_mark]
root         30      2  0 09:35 ?        00:00:00 [crypto]
root         38      2  0 09:35 ?        00:00:00 [kthrotld]
root         40      2  0 09:35 ?        00:00:00 [kmpath_rdacd]
--More--

To kill or stop a process use the kill

Syntax : kill <process ID>

[root@localhost ~]# kill 40   # End a Process

Other Useful ps commands are :
ps -e
ps -eF
ps -ely

Linux Commands to Manage Users & Groups

To create a New User in Linux we can use the command useradd command and set a password for the user to use passwd command.

Syntax :

To add a New User :

useradd <Username>

Set/Reset Password of any User

passwd <Username>

[root@localhost ~]# useradd helpdesk   # Create a New User

[root@localhost ~]# passwd helpdesk   # Set Password for User
Changing password for user helpdesk.
New password: 
Retype new password: 
passwd: all authentication tokens updated successfully.

To confirm if the user created it successfully or not we can check the /etc/passwd file. Refer to the output below.

[root@localhost ~]# cat /etc/passwd | grep helpdesk   # Confirm the Newly created User
helpdesk:x:1001:1001::/home/helpdesk:/bin/bash

To add a new group use groupadd command.

Syntax : groupadd <GROUP NAME>

[root@localhost ~]# groupadd admins   # Create a New Group

[root@localhost ~]# cat /etc/group | grep admins   # Confirm the Newly Created Group
admins:x:1002:

Create a New User and add to a Group. Here I am creating a user named test2 and adding to group admins.

Syntax :  useradd -g <GROUP NAME> <USER NAME>

[root@localhost ~]# useradd -g admins test2   # Create a New User and Add in to a Group
[root@localhost ~]# cat /etc/passwd | grep test2
test2:x:1003:1002::/home/test2:/bin/bash

To add a Supplementary group to an existing user you have to use usermod command with options -a and -G, Refer to the command below.

Note: Supplementary Group is also referred to as Secondary Group.

[root@localhost ~]# usermod -a -G admins itsmarttricks# Add a Secondary group to a existing User
[root@localhost ~]# cat /etc/group | grep admins
admins:x:1002:itsmarttricks

To add already existing user to multiple groups use below command, Here I am add user test to Multiple groups i.e.admins and coders
[root@localhost ~]# usermod -a -G admins,coders test   # Add user to multiple Groups

To confirm the if users are added to respective groups or not we can use the below command.

[root@localhost ~]# cat /etc/group
admins:x:1002:itsmarttricks,test
coders:x:1003:test

As we can see above admins group has two users i.e. itsmarttricks and test and the coders group has one i.e. test that we have added now.

Also Read – Best Yum Command With Examples A Package Manager In Rhel/Centos/Fedora

Disk Related Linux Commands

To List Available disks and partitions we can use fdisk command with option -l

[root@localhost ~]# fdisk -l   # List the disks and partitions

Disk /dev/sda: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x000c0d0d

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048     2099199     1048576   83  Linux
/dev/sda2         2099200    41943039    19921920   8e  Linux LVM

To check all mounted partitions or devices we can use df command with option -h, We can check File System Name, Total Size of the Disk, Used Disk Space, Mount Point by using df -h command. Refer to the output below.

[root@localhost ~]# df -h   # List mounted disks & partitions
Filesystem           Size  Used Avail Use% Mounted on
/dev/mapper/cl-root   17G  3.3G   14G  20% /
devtmpfs             473M     0  473M   0% /dev
tmpfs                489M  144K  489M   1% /dev/shm
tmpfs                489M  7.1M  482M   2% /run
tmpfs                489M     0  489M   0% /sys/fs/cgroup
/dev/sda1           1014M  173M  842M  18% /boot
tmpfs                 98M   12K   98M   1% /run/user/0
/dev/sr0             4.1G  4.1G     0 100% /run/media/root/CentOS 7 x86_64

Also, you can use the only df command to get disk and partition information.

[root@localhost ~]# df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda2       18208184 3007176  14269424  18% /
tmpfs             506040     228    505812   1% /dev/shm
/dev/sda1         289293   34673    239260  13% /boot

To check all mounted devices you can use the mount command. Refer to the output below.

[root@localhost ~]# mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime,seclabel)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
devtmpfs on /dev type devtmpfs (rw,nosuid,seclabel,size=484112k,nr_inodes=121028,mode=755)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,seclabel)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,seclabel,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,nodev,seclabel,mode=755)

Compression and Archiving related Linux Commands

Compress a file using gzip command with option -c. The extension of the gzip-compressed file is .gz.

Where :

c – To create a gzip file

[root@localhost ~]# gzip -c test.txt > test.txt.gz  # Create gzip file

UnCompress/Extract .gz file using command gunzip.

[root@localhost ~]# gunzip test.txt.gz   # Extract a gzip file
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  Videos
Desktop          Downloads  Music                 Public    test.txt

Compress a file using the bzip2 command with option -c. The extension of the bzip2 compressed file is .bz2.

[root@localhost ~]# bzip2 -c test.txt > test.txt.bz2  # Create a bzip2 file
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  test.txt.bz2
Desktop          Downloads  Music                 Public    test.txt   Videos

UnCompress/Extract .bz2 file using command gunzip.

[root@localhost ~]# bunzip2 test.txt.bz2   # Extract a bzip2 file
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  Videos
Desktop          Downloads  Music                 Public    test.txt

Compress a file using the zip command. The extension of the bzip2 compressed file is .zip.

[root@localhost ~]# zip test.txt.zip test.txt    # create zip file
  adding: test.txt (stored 0%)
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  test.txt.zip
Desktop          Downloads  Music                 Public    test.txt   Videos

Compress a Directory using the zip command.

[root@localhost ~]# zip data.zip data/   # Compress a Directory using zip command
  adding: data/ (stored 0%)
[root@localhost ~]# ls
anaconda-ks.cfg  data.zip  Documents  initial-setup-ks.cfg  Pictures  Templates
data             Desktop   Downloads  Music                 Public    Videos

Extract/Unzip a zip compressed file.

[root@localhost ~]# unzip test.txt.zip   # Extract a zip file
Archive:  test.txt.zip
 extracting: test.txt                
[root@localhost ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates  test.txt.zip
Desktop          Downloads  Music                 Public    test.txt   Videos

tar is used as a backup tool in Linux Systems. The extension of the tar file is .tar. By using the tar command we can archive both files and directories. So follow the below command to archive a directory.

Where :

c – To create a tar file
v – For Verbose
f – For file

[root@localhost ~]# tar -cvf data.tar data/   # Create a tar archive File
data/
data/file1.txt
data/file2.txt
data/file3.txt
data/file4.txt
data/file5.txt
[root@localhost ~]# ls
anaconda-ks.cfg  data.zip   Downloads             Pictures   Videos
data             Desktop    initial-setup-ks.cfg  Public
data.tar         Documents  Music                 Templates

To extract a tar file.

Where :

x – to extract a file

[root@localhost ~]# tar -xvf data.tar   # Extract a tar archive file
data/
data/file1.txt
data/file2.txt
data/file3.txt
data/file4.txt
data/file5.txt
[root@localhost ~]# ls
anaconda-ks.cfg  data.tar  Documents  initial-setup-ks.cfg  Pictures  Templates
data             Desktop   Downloads  Music                 Public    Videos

Create a tar archive with gzip compression.

Where :

z – for gzip compression

[root@localhost ~]# tar -czvf data.tar.gz data/   # Create a tar archive with gzip compression
data/
data/file1.txt
data/file2.txt
data/file3.txt
data/file4.txt
data/file5.txt
[root@localhost ~]# ls
anaconda-ks.cfg  data.tar.gz  Documents  initial-setup-ks.cfg  Pictures  Templates
data             Desktop      Downloads  Music                 Public    Videos

Extract a tar archived with gzip compressed file.

[root@localhost ~]# tar -xzvf data.tar.gz  # Extract a tar archived with gzip compressed file
data/
data/file1.txt
data/file2.txt
data/file3.txt
data/file4.txt
data/file5.txt
[root@localhost ~]# ls
anaconda-ks.cfg  data.tar.gz  Documents  initial-setup-ks.cfg  Pictures  Templates
data             Desktop      Downloads  Music                 Public    Videos

Create a tar archive with bzip2 compression.

Where :

j – for bzip2 compression

[root@localhost ~]# tar -cjvf data.tar.bz2 data/   # Create a tar archive with bzip2 compression
data/
data/file1.txt
data/file2.txt
data/file3.txt
data/file4.txt
data/file5.txt
[root@localhost ~]# ls
anaconda-ks.cfg  data.tar.bz2  Documents  initial-setup-ks.cfg  Pictures  Templates
data             Desktop       Downloads  Music                 Public    Videos

Extract a tar archive with bzip2 compressed file

[root@localhost ~]# tar -xjvf data.tar.bz2  # Extract a tar archived with bzip2 compressed file
data/
data/file1.txt
data/file2.txt
data/file3.txt
data/file4.txt
data/file5.txt
[root@localhost ~]# ls
anaconda-ks.cfg  data.tar.bz2  Documents  initial-setup-ks.cfg  Pictures  Templates
data             Desktop       Downloads  Music                 Public    Videos

System Information Related Linux Commands

To check memory-related information we can check /proc/meminfo file.

[root@localhost proc]# cat /proc/meminfo   # Check Memory Information

To check disk statistics use the below command.

[root@localhost proc]# cat /proc/diskstats   # Check Disk Information

To know the RAID device status you can use the below command.

[root@localhost proc]# cat /proc/mdstat   # Check RAID disks information

To check the CPU Information use the below command.

[root@localhost proc]# cat /proc/cpuinfo   # Check CPU Information

To check your partition status you can use the below command, the same result you can get by using command fdisk -l command.

[root@localhost proc]# cat /proc/partitions   # Check Partition Information
major minor  #blocks  name

   8        0   20971520 sda
   8        1     307200 sda1
   8        2   18631680 sda2
   8        3    2031616 sda3

/proc/mounts file will show you all mounted disks or devices. the same result you can get by using the mount command.

[root@localhost proc]# cat /proc/mounts   # Check mounted disks information

To check your system’s uptime use the below command.

[root@localhost proc]# cat /proc/uptime   # Check System UP Time
2163.72 1783.93

To check the Server version. The same output you will get by uname -a command.

[root@localhost proc]# cat /proc/version    # Check OS Information
Linux version 2.6.32-642.el6.x86_64 (mockbuild@worker1.bsys.centos.org) (gcc version 4.4.7 20120313 (Red Hat 4.4.7-17) (GCC) ) #1 SMP Tue May 10 17:27:01 UTC 2016

/proc/swaps will show you the swap partition information.

[root@localhost proc]# cat /proc/swaps   # Check swap Partition Info.
Filename                                Type            Size    Used    Priority
/dev/sda3                               partition       2031612 8       -1

you can pull complete system information like disk report, raid device report..etc by using sosreport command.

[root@localhost ~]# sosreport   # Pull System Information Report

After creating a new partition you have to mount that partition in /etc/fstab file, then only you can use that partition to store data. fstab referred to as Filesystem Table. Refer to the sample /etc/fstab file below.

[root@localhost ~]# cat /etc/fstab    # Overview on Filesystem Table

#
# /etc/fstab
# Created by anaconda on Sun Dec 25 03:05:56 2016
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=25f0e1e0-0f54-42f3-b609-d95ce77c783f /                       ext4    defau$
UUID=51ea032d-f7af-4bb3-8aa9-8fa4428bc362 /boot                   ext4    defau$
UUID=e9cf7e2b-b945-4074-a63f-b114a3477f42 swap                    swap    defau$
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0

Permissions Related Linux Commands

There are two ways by which we can apply permission to files and directories in Linux. One is the Alphabetical way and the second is the Numerical Way. Below explained Permission related Linux commands with examples.

Alphabetical Permission

Permission in Linux is looks something like this (Divided into 10 Bits) :

– – – – – – – – – –

For our understanding let’s convert all 10 bit’s in Numbers.

–   –   –   –  –  –  –  –  –  –

1  2  3  4  5  6  7  8  9  10

  1. Out of which First Bit (i.e  1 ) is for File or Folder Identification () Where if the first bit is “” then it’s a file and if it’s “d” then it’s a directory.
  2. The next three-bit (i.e 2 3 4) is for Owner (– – –) and Owner is Identified as alphabet “u
  3. The next three-bit (i.e 5 6 7) is for Group (– – –) and Group is Identified as alphabet “g
  4. & Last three-bit (i.e 8 9 10)is for Other (– – –) and Other is Identified as alphabet “o

First, have look at alphabetical permission :

r – Read
w – Write
e – Execute

To Add permission we have to use the “+” Symbol and for Remove Permission we have to use the “” Symbol.

We can check the permission of any file or directory by the ls -l command.

Example: 1

In our first example the file named test.txt having permission “-rw-r–r–“, so let’s divide the permission bits of file test.txt.
The first bit is “” which means it’s a File.
r w –” – Means Owner having Read & Write Permission because 2nd bit contains r and 3rd bit contains w.
r – –” – Means Group having Read Access.
r – –” – Means Others having Read Access.

Now I am going to give full access to Everyone i.e. User, Group & Others by using the chmod command.

[root@localhost data]# ls -l
total 0
-rw-r--r--. 1 root root 0 Mar  8 09:56 test.txt  # Now File having Permission i.e. -rw-w--w--
[root@localhost data]# chmod ugo+rwx test.txt    # Giving Full Access to Everyone
[root@localhost data]# ls -l
total 0
-rwxrwxrwx. 1 root root 0 Mar  8 09:56 test.txt  # Now File having Permission i.e. -rwxrwxrwx

Example: 2

Remove Write and Execute Permission from Group & Others

[root@localhost data]# chmod go-wx test.txt   # Change Permission in Alphabatical Way
[root@localhost data]# ls -l
total 0
-rwxr--r--. 1 root root 0 Mar  8 09:56 test.txt

Example : 3

Add Write Permission to Group & Others

[root@localhost data]# chmod go+w test.txt 
[root@localhost data]# ls -l
total 0
-rwxrw-rw-. 1 root root 0 Mar  8 09:56 test.txt

Numerical Permission

Numerical Permission in Linux as shown below.

4 – Read
2 – Write
1 – Execute

Steps to apply permission to User, Group & Others

Suppose you want to give Full Permission to Owner i.e. Read+Write+Execute to the file text.txt then in Numerical way it’s like

4+2+1 = 7   Read+Write+Execute

& If you would like to give only Read access to Group and Others then it’s like

For Groups – 4

For Others – 4

So the overall command would be chmod 744 test.txt.

Now let’s take some examples so that you can understand properly.

Example: 1

Giving Full access to File test.txt

[root@localhost data]# ls -l
total 0
-rwxrw-rw-. 1 root root 0 Mar  8 09:56 test.txt
[root@localhost data]# chmod 777 test.txt   # Change Permission in Numerical Way
[root@localhost data]# ls -l
total 0
-rwxrwxrwx. 1 root root 0 Mar  8 09:56 test.txt

Example: 2

Giving Read & Write Permission to all (User, Group & Others).

[root@localhost data]# chmod 666 test.txt 
[root@localhost data]# ls -l
total 0
-rw-rw-rw-. 1 root root 0 Mar  8 09:56 test.txt

Example : 3

Giving Full Access to Owner and Read Access to Group & Others.

[root@localhost data]# chmod 744 test.txt 
[root@localhost data]# ls -l
total 0
-rwxr--r--. 1 root root 0 Mar  8 09:56 test.txt
[root@localhost data]# chmod 755 test.txt 

We can check the Owner of the file by the ls -l command, Currently, the owner of the test.txt file is the root (Highlighted in Red Color on the output below). We can change the ownership of the file by using the chown command.

Ownership Format :

-rwxr-xr-x. 1 User Group 0 Mar 8 09:56 test.txt

[root@localhost data]# ls -l
total 0
-rwxr-xr-x. 1 root root 0 Mar  8 09:56 test.txt

Here I am changing the Ownership of the file from user root to user itsmarttricks.

[root@localhost data]# chown itsmarttricks:eitsmarttricks test.txt   # Change Ownership of a File
[root@localhost data]# ls -l
total 0
-rwxr-xr-x. 1 itsmarttricks itsmarttricks 0 Mar  8 09:56 test.txt

Now let’s change the ownership of the directory with all its content Recursively. To do so we have to use chown command with option -R.

[root@localhost data]# ls database/
file1.txt  file2.txt  file3.txt  file4.txt  file5.txt
[root@localhost data]# ls -l database/
total 0
-rw-r--r--. 1 root root 0 Mar  8 10:01 file1.txt
-rw-r--r--. 1 root root 0 Mar  8 10:01 file2.txt
-rw-r--r--. 1 root root 0 Mar  8 10:01 file3.txt
-rw-r--r--. 1 root root 0 Mar  8 10:01 file4.txt
-rw-r--r--. 1 root root 0 Mar  8 10:01 file5.txt
[root@localhost data]# chown -R itsmarttricks:itsmarttricks database/  # Change Ownership of Directory Recursively
[root@localhost data]# ls -l
total 4
drwxr-xr-x. 2 itsmarttricks itsmarttricks 4096 Mar  8 10:01 database
-rwxr-xr-x. 1 itsmarttricks itsmarttricks 0 Mar  8 09:56 test.txt
[root@localhost data]# ls -l database/
total 0
-rw-r--r--. 1 itsmarttricks itsmarttricks 0 Mar  8 10:01 file1.txt
-rw-r--r--. 1 itsmarttricks itsmarttricks 0 Mar  8 10:01 file2.txt
-rw-r--r--. 1 itsmarttricks itsmarttricks 0 Mar  8 10:01 file3.txt
-rw-r--r--. 1 itsmarttricks itsmarttricks 0 Mar  8 10:01 file4.txt
-rw-r--r--. 1 itsmarttricks itsmarttricks 0 Mar  8 10:01 file5.txt

Package installation and Service-Related Linux Commands

Install a package using rpm commands.

Where :

i – Install a Package
v – For Verbose
h – for # output

   
# rpm -ivh dhcp-3.0.5-23.el5.x86_64.rpm   # Install Package using rpm command
   warning: dhcp-3.0.5-23.el5.x86_64.rpm: Header V3 DSA signature: NOKEY, key ID 37017186
   Preparing...                ########################################### [100%]
      1:dhcp                   ########################################### [100%]

Install a Package using yum command. In the case of yum when we try to install a package, it retrieves the package information from the yum repository package manager server and makes it available to us.

[root@localhost ~]# yum -y install vsftpd   # Install a Package using yum command
Loaded plugins: fastestmirror, refresh-packagekit, security
Setting up Install Process
Loading mirror speeds from cached hostfile
 * base: mirror.nbrc.ac.in
 * extras: mirrors.vinahost.vn
 * updates: mirrors.vonline.vn
Resolving Dependencies
--> Running transaction check
---> Package vsftpd.x86_64 0:2.2.2-21.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

================================================================================
 Package          Arch             Version                 Repository      Size
================================================================================
Installing:
 vsftpd           x86_64           2.2.2-21.el6            base           155 k

Transaction Summary
================================================================================
Install       1 Package(s)

Total download size: 155 k
Installed size: 340 k
Downloading Packages:
vsftpd-2.2.2-21.el6.x86_64.rpm                           | 155 kB     00:02     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : vsftpd-2.2.2-21.el6.x86_64                                   1/1 
  Verifying  : vsftpd-2.2.2-21.el6.x86_64                                   1/1 

Installed:
  vsftpd.x86_64 0:2.2.2-21.el6                                                  

Complete!

Start/Restart/Stop a Service a Service.

[root@localhost ~]# /etc/init.d/vsftpd start   # To start a Service

[root@localhost ~]# service vsftpd status   # Check the Service status
vsftpd (pid 3168) is running...

[root@localhost ~]# /etc/init.d/vsftpd restart   # To Restart a Service

[root@localhost ~]# /etc/init.d/vsftpd stop   # To Stop a Service

Start a Service at startup.

chkconfig --level 35 vsftpd on   # Start a Service on Startup

We tried to include all possible basic Linux commands. That’s all, In this article, we have explained Complete Unix Commands And Basic Linux Commands. I hope you enjoy this article. If you like this article, then just share it. If you have any questions about this article, please comment.

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Mangesh Dhulap

This is Mangesh Dhulap the Founder and Editor of IT SMART TRICKS have 6+ years of Industrial Experience. We expect from our visitors to like, share, and comment on our posts.

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