There are four main user administration files:
- /etc/passwd: User accounts
- /etc/shadow: User password
- !! means password does not exist
- /etc/group: Group information
- /etc/gshadow: Group passwords
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useradd: -d→different home directory, -u→user id, -g→group id, -G→ multi group (secondary), -M→no home folder, -e→expiry, -c→comment, -s→custom shell, -f→password expire, -m→ create home directory
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usermod: -c→comment, -d→modify home directory, -e→expiry, -g→primary group, -a→add to secondary group, -G→secondary group, -l→login name (username), -L→lock the account, -U →unlock account, -d→default home dir, -s→change shell, -r → system account
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userdel
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groupadd: -f→force, -g→gid, -r→system group
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groupmod: -g→new gid, -n→new name
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groupdel
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gpasswd: -a→add user, -d→delete user, -r→remove password & change password of a group (gpasswd groupname)
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newgrp: Log in to a new group, change the gid