Grep for groups with more than one user

Question

We are getting ready to migrate to Active Directory-based Samba, from the old style domain. Currently all our groups are flat - users belong to groups, but groups can't belong to other groups. Since I want to change that, I need to list all the groups with users.

The catch is that there are thousands of users, and thousands of groups. What I need is to list the groups with 2 or more members, then only show the group name on the command line. This should eliminate user-groups, or groups with only one user.

How can I do this in Debian?

Answer 1

Generally,

getent group | awk -F ':' '$4 ~ "," {print $1}'

If the 4th colon-delimited field (user list) of the group list contains a comma, then print the first colon-delimited field (group name).

Answer 2

Probably not the best way to do it, but this might work:

awk -F: '$NF ~ "," { print $1 }' /etc/group

Answer 3

as group members are comma-delimited, only multi-member groups will have commas. From these group-file lines, show only the line content before the first colon.

grep , /etc/group | cut -d: -f 1