Is there a way to only edit the GID on /etc/passwd file using chef?

Question

Can we use a Chef resource to change the GID from 101 to 100(or any other number) in /etc/passwd file?libuuid:x:100:101::/var/lib/libuuid:

For all the GID's with 101 in /etc/passwd if one needs to change the GID, what is the way to do it using Chef resources?

Answer 1

utilize the user resource

user 'a user' do
  comment 'A random user'
  uid 1234
  gid 'groupname'
  home '/home/random'
  shell '/bin/bash'
  password '$1$JJsvHslasdfjVEroftprNn4JHtDi'
end

Answer 2

Before suggesting a solution for this, I would like point out 2 things:

1. Hand/scripted editing of /etc/passwd file is best avoided as it can lead to issues.
2. Chef is not the tool for editing files. Chef resources are converged on the node they run, and bring the state of the resource to state defined in the recipe.

If you would still like to use Chef, you could use Ruby code inside ruby_block resource.

However, the cleanest way to handle this would be identify the users (separately) and use the user resource.

Example:

# This will set gid as 1001 for user1, user2, user3
%w(
  user1
  user2
  user3
).each do |u|
  user u do
    # add any other properties as required
    gid '1001'
  end
end

Update:

A sample file /tmp/userlist with below contents:

john:x:100:101::/bin/bash:
david:x:207:100::/bin/bash:
joe:x:100:101::/bin/nologin:
mike:x:101:100::/bin/bash:
rich:x:103:207::/bin/bash:
fred:x:105:111::/bin/nologin:

Not an expert at Ruby, but here it goes. The following ruby_block will read lines from a file, and create a new file with the lines with GID 101 replaced:

ruby_block "Write file" do
  block do
    puts
    userlist = File.readlines('/tmp/userlist')
    fp = File.open('/tmp/newuserlist', mode='w')
    userlist.each do |line|
      gid = line.split(':')[3]
      if gid == '101'
        fp.write line.sub(/.*\K101/, '1001')
      else
        fp.write line
      end
    end
    fp.close
  end
end

Note: There may be a cleaner and easier way to do this with Ruby, or with some other language or even Shell script. Do consider the same.