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Asked: 2026-05-11T01:44:07+00:00

I am putting together a Samba-based server as a Primary Domain Controller, and ran

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I am putting together a Samba-based server as a Primary Domain Controller, and ran into a cute little problem that should have been solved many times over. But a number of searches did not yield a result. I need to be able to remove an existing user from an existing group with a command line script. It appears that the usermod easily allows me to add a user to a supplementary group with this command:

usermod -a -G supgroup1,supgroup2 username

Without the ‘-a’ option, if the user is currently a member of a group which is not listed, the user will be removed from the group. Does anyone have a perl (or Python) script that allows the specification of a user and group for removal? Am I missing an obvious existing command, or well-known solution forthis? Thanks in advance!

Thanks to J.J. for the pointer to the Unix::Group module, which is part of Unix-ConfigFile. It looks like the command deluser would do what I want, but was not in any of my existing repositories. I went ahead and wrote the perl script using the Unix:Group Module. Here is the script for your sysadmining pleasure.

#!/usr/bin/perl # # Usage:   removegroup.pl login group # Purpose: Removes a user from a group while retaining current primary and #          supplementary groups. # Notes:   There is a Debian specific utility that can do this called deluser, #          but I did not want any cross-distribution dependencies # # Date:   25 September 2008  # Validate Arguments (correct number, format etc.) if ( ($#ARGV < 1) || (2 < $#ARGV) ) {   print '\nUsage: removegroup.pl login group\n\n';   print 'EXIT VALUES\n';   print '     The removeuser.pl script exits with the following values:\n\n';   print '     0 success\n\n';   print '     1 Invalid number of arguments\n\n';   print '     2 Login or Group name supplied greater than 16 characters\n\n';   print '     3 Login and/or Group name contains invalid characters\n\n';   exit 1; }  # Check for well formed group and login names if ((16 < length($ARGV[0])) ||(16 < length($ARGV[1]))) {   print 'Usage: removegroup.pl login group\n';   print 'ERROR: Login and Group names must be less than 16 Characters\n';   exit 2; }  if ( ( $ARGV[0] !~ m{^[a-z_]+[a-z0-9_-]*$}) || ( $ARGV[0] !~ m{^[a-z_]+[a-z0-9_-]*$} ) ) {   print 'Usage: removegroup.pl login group\n';   print 'ERROR: Login and/or Group name contains invalid characters\n';   exit 3; }  # Set some variables for readability $login=$ARGV[0]; $group=$ARGV[1];  # Requires the GroupFile interface from perl-Unix-Configfile use Unix::GroupFile;  $grp = new Unix::GroupFile '/etc/group'; $grp->remove_user('$group', '$login'); $grp->commit(); undef $grp; exit 0;
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  1. Web Link: http://www.ibm.com/developerworks/linux/library/l-roadmap4/

    To add members to the group, use the gpasswd command with the -a switch and the user id you wish to add:

    gpasswd -a userid mygroup

    Remove users from a group with the same command, but a -d switch rather than -a:

    gpasswd -d userid mygroup

    ‘man gpasswd’ for more info…

    I looked for ages to find this. Sometimes it takes too much effort not to reinvent the wheel…

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