Changing a username under Arch (or any flavor of Linux) is safe and easy when done properly. You can also change the associated groupname for the user if you wish. Following the procedure below will do just this retaining your UID/GID for the affected user thus not roaching any file permissions you have setup.
Change A User's Login
This will change only the user's login name.
# usermod -l newname oldname
Change A User's $HOME
This will only change the home directory of username
# usermod -d /my/new/home username
Change A User's $HOME and Move Contents
This will move the contents of username's home directory to
/my/new/home and set the user's home directory to the new one.
# usermod -md /my/new/home username;
Change Group Name
If you want to change the user's group also:
# groupmod -n newname oldname
For further information see the man pages for usermod and groupmod.
Manually With /etc/passwd
When possible, you should use the above commands to modify usernames and home directories, however for those of you who want to know the 'guts' of the operations, it can be done manually.
/etc/passwd File Format
Each line of the file follows a specific format. There are seven fields, each delimited by (":") a colon.
<login name>:<password>:<numerical UID>:<numerical GID>:<Real name/comments>:<home directory>:<user command interpreter>
- <login name> This field can not be blank. Standard *NIX naming rules apply.
- <password> would be an encrypted password, however it should be marked with a lowercase "x" (without quotes) to signify the password is located in
- Each user and group name has a corresponding numerical UID and GID (User ID and Group ID). In Arch, the first login name (after root) is UID 1000 by default. Subsequent UID/GID entries for users should be greater than 1000. GID should match the primary group for the particular user. Numeric values for GIDs are listed in
- <Real name/comments> is used by services such as finger. This field is optional and may be left blank.
- <home directory> is used by the login command to set the
$HOMEenvironment variable. Several services with their own users use "/" which is safe for services, but not recommended for normal users.
- <user command interpreter> is the path to the user's default shell. This is normally Bash, but there are several other command line interpreters available. The default setting is "/bin/bash" (without quotes) for users. If you use another CLI, set the path to it here. This field is optional.
jack:x:1001:100:Jack Smith,some comment here,,:/home/jack:/bin/bash
Broken down, this means: user jack (who's password is in
/etc/shadow) is UID 1001 and his primary group is 100 (users). Jack Smith is his full name and there is a comment associated to his account. His home directory is
/home/jack and he is using Bash.
- If you are using sudo make sure you update your
/etc/sudoersto reflect the new username(s) (via the visudo command as root)
- If you modified your PATH statement in your
~/.bashrc, make sure you change it to reflect the new username
- Likewise, be sure you change any config file such as
/etc/rc.localor whatever if you are pointing it to a script or mountpoint, etc. within the old user's home directory.
- I had to repeat the procedure to enable spell checking in Firefox or else the check-as-you-type spelling did not work for me after renaming my user.
- I had to reinstall my Thunderbird addons (Enigmail) after renaming my user.
- Anything on your system (desktop shortcuts, shell scripts, etc.) that uses an absolute path to your home dir (i.e.
/home/oldname) will need to be changed to reflect your newname. To avoid these problems in shell scripts, simply use the
$HOMEvariables for home directories.