Basic Linux commands

To list all the users in system.

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cat /etc/passwd

To list all the groups in system.

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cat /etc/group

To add new user.

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sudo adduser username

To add a user to sudo group.

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sudo usermod -aG sudo username

To delete user.

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sudo deluser username

To delete user and his home directory

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sudo deluser --remove-home username

To add a group to directory

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sudo chgrp -R username directoryname

To make directory read write access to group

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sudo chmod g+rwx -R directoryname