Linux Basic Commands

How to change Shell in Linux?

1. cat /etc/shells (In that file you will see all shell that support by OS)
2. To change Shell "chsh -s /bin/shell name" "chsh -s /bin/tcsh"
3. Change Shell for user "chsh -s /bin/shell name Username" "chsh -s /bin/tcsh jiten"

What is the command to check user group name , group ID , UID ?

id username

id jiten (This command will show you UID , GID , group name)

What is the command to check user account expiry date info?

chage -l username

chage -l jiten (This command will show you user related information)

User add command options?

what is the command to create user in different directory?

useradd -d /home/directory name/ username   username

useradd -d /home/sale/jiten jiten

what is the command to user with specific user ID?

useradd -u UID number user name

useradd -u 2222 jiten

what is the command to user with specific GID?

useradd -u UID number -g GID number username

useradd -u 3323 -g 400 jiten

or 

useradd -g 391 jiten

what is the command to add user in multiple group?

useradd -G group name username

useradd -G postfix,sale,market jiten

(To separate groups we use "," sign )

what is the command  to add user without HOME directory?

useradd -M username

useradd -M jiten

what is the command to add user with  account expiry date?

useradd -e yyyy-mm-dd username 

useradd -e 2013-06-01 jiten

what is the command to set user expiry date and days?

useradd -e 2013-06-01 -f 45 (days) username

useradd -e 2013-06-01 -f 45 jiten  (user command with expiry in 45 days)

what is the command to set comment on user ?

useradd -c "Hello I am sales team" user name

useradd -c "Hello I am sales team" jiten

what is the command to change user shell?

useradd -s /sbin/nologin username

useradd -s /sbin/nologin jiten

Add user with specific Home directory , Default shell and Custom comment?

useradd -m -d /home/sales/username -s /bin/bash -c "sales person" -U username

useradd -m -d /home/sales/jiten -s /bin/bash -c "sales person" -U jiten 

Add user with home directory, custom shell , custom comment and UID/GID?

useradd -m -d /home/sales/username -s /bin/bash -c "hello" -u 6000 -g 6000 username

useradd -m -d /home/sales/jiten -s /bin/bash -c "hello" -u 6000 -g 6000 jiten

Add user with home directory , no shell , custom comment and UID?

useradd -m -d /home/sales/username -s /sbin/nologin -c "how are you team" -u 1020 username

useradd -m -d /home/sales/jiten -s /sbin/nologin -c "How are you team" -u 1020 jiten

Add user with home directory, shell,custom skell/comment and user ID?

useradd -m -d /home/sales/username -k /etc/custom.skell -s /sbin/tcsh -c "sales member" -u 3021 username

useradd -m -d /home/sales/jiten -k /etc/custom.skell -s /sbin/tcsh -c "sales member" -u 3021 jiten

Add user without home directory, No shell  and no group ?

useradd -M -N -r -s /bin/false username

useradd -M -N -r -s /bin/false jiten

What is the usermod command and it use ?

we use usermod command to modify user details

what is the command to change user home directory ?

usermod -d newdirectory name  olddirectoryname

usermod -d /home/testnet jiten (This command will not copy the content of jiten user directory to testnet directory)

what is the command to change user home directory with it content?

usermod -d newdirectory name -m olddirectory name

usermod -d /home/testnet -m jiten (When you will run this command it will copy jiten directory content to testnet directory)

what is the command to add group in user?

usermod -G group name user name

usermod -G developer jiten

what is the command to add group with exist group?

usermod -aG groupname username

usermod -aG developer jiten

what is the command to change user primary group?

usermod -g groupname username

usermod -g developer jiten

id username 

id jiten

what is the command to lock user?

usermod -L username

usermod -L jiten

what is the command to unlocking user?

usermod -U username 

usermod -U jiten

what is the command to change expiry date of user account?

usermod -e yyyy-mm-dd username

usermod -e 2016-12-30 jiten

what is the command to change login name ?

usermod -l newname username

usermod -l jitenjha jiten

what is the command to change login password?

usermod -p newpassword username

usermod -p newpassword jiten

what is the command to change user shell?

usermod -s /bin/bash username

usermod -s /bin/bash jiten