User & Group Management
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Adding Users
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Adding Users
To add a user, the useradd command can be used.
useradd usernameIf you want to create a user with it's own home directory, this can be done using the -m flag:
useradd -m usernameThe default contents of a users home directory are defined within the /etc/skel directory, please see HERE for more info on this.
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Adding a system user
useradd -r usernameOnce created, you'll want to restrict the account by disabling the ability for login, as mentioned here
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Additional options:
-e -expires
-e 2023/12/31-c - comment
-c "full name"-s -shell
-s /bin/sh------------------------------------------------------------------------------------------------------------------------------------------------
Groups
When creating a user, you can also specify groups to add the user to, this is done using the -G flag:
useradd -G groupname username------------------------------------------------------------------------------------------------------------------------------------------------
Comments
When creating a user, you can also opt to add a comment using the -c flag, for example this could be a name:
useradd -c "comment" username====================================================================================
Passwords
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Set Password
Once a user has been created, you can add a password using the passwd command:
passwd usernameOnce run, you'll be prompted to enter a new password
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Changing password
Changing a users password can be done using the passwd command when signed in as that user.
You can either SSH to the server directly using the required user, or access as root and use su- username to access the user. Once accessed, the passwd command can be run alone to change the password:
passwdYou can also change a users password using root:
passwd username------------------------------------------------------------------------------------------------------------------------------------------------
Additional Options:
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Temporary Password
When setting a password, you're able to set a temporary placeholder password that can be used to log in by the user, upon logging in the user will be prompted to change to a password of their choice. This can be achieved by using the -e flag after setting a password
passwd username #set as temp password
passwd -e #sets password as expired====================================================================================
Deleting Users
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Deleting Users
Users can be deleted using the userdel command:
userdel usernameThe above command only removes the user from the system, without removing their home directory.
Remove user and home directory
userdel -r username====================================================================================
Modifying Users
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Post Creation, users can be modified using the usermod command.
Add User To Group
usermod -a -G groupname username------------------------------------------------------------------------------------------------------------------------------------------------
Lock/Unlock Users
Lock User Login
usermod -L usernameUnlock User Login
usermod -U username------------------------------------------------------------------------------------------------------------------------------------------------
Disable login access
usermod -s /sbin/nologin usernameor we can use the change shell (chsh) command:
chsh -s /bin/nologin username------------------------------------------------------------------------------------------------------------------------------------------------
Change User Home Directory
usermod -d /pathtonewhome username
chown username:usergroup /pathtonewhome====================================================================================
Groups
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Viewing Groups
groups username------------------------------------------------------------------------------------------------------------------------------------------------
Adding Groups
New groups can be created using the groupadd command:
groupadd groupname------------------------------------------------------------------------------------------------------------------------------------------------
Managing group users
Users can be added to a group with 2 main methods,
- They can be added when initially created, as mentioned above
- They can be added after creation using the usermod command, as mentioned above
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Removing groups
Groups can be removed using the groupdel command, note that this doesn't delete the users that are part of this group.
groupdel groupname------------------------------------------------------------------------------------------------------------------------------------------------
Modifying Groups
There are various group properties that can be modified using the groupmod command.
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Change Group Name
groupmod -n newname oldname------------------------------------------------------------------------------------------------------------------------------------------------
Change Group ID
groupmod -g NEWID groupname------------------------------------------------------------------------------------------------------------------------------------------------