user and group management commands in linux

These user and group management commands should work on linux, unix and mac os, only a few might not work across all systems.

Show all existing users
[code language=”text”]
awk -F: ‘{ print $1 }’ /etc/passwd
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Add a new user “ken”
[code language=”text”]
sudo adduser ken
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Grant root access to the user “ken”
Type
[code language=”text”]
sudo /usr/sbin/visudo
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Add the below
[code language=”text”]
ken ALL=(ALL:ALL) ALL
[/code]

after
[code language=”text”]
root ALL=(ALL:ALL) ALL
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To delete the user “ken”
[code language=”text”]
sudo userdel ken
[/code]

Check if anyone can execute commands as root
[code language=”text”]
cat /etc/sudoers
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Change the password of the existing user “ken”
[code language=”text”]
sudo passwd ken
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To lock the user account “ken”
[code language=”text”]
sudo passwd -l ken
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To unlock the user account “ken”
[code language=”text”]
sudo passwd -u ken
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Add the user “ken” to the user group “users”
[code language=”text”]
sudo usermod -a -G users ken
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Show the groups the user “ken” belongs to
[code language=”text”]
groups ken
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Find all the existing groups
[code language=”text”]
cat /etc/group | cut -d: -f1
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Change the primary group of the user “ken” to the group “users”
[code language=”text”]
sudo usermod -g users ken
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To add a group “testers”
[code language=”text”]
groupadd testers
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To delete a group “testers”, users under this group needs to be removed first if any.
[code language=”text”]
groupdel testers
[/code]

List all users under the user group “users”. It will not list users to whom this group is primary.
[code language=”text”]
egrep "^users" /etc/group
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