Re: [gentoo-dev] [PATCH] acct-user.eclass: don't modify existing user by default

[Michael Orlitzky <mjo@gentoo.org>]

On 1/3/21 8:35 PM, Thomas Deutschmann wrote:
> Modifying an existing user is a bad default and makes Gentoo
> special because it is common for system administrators to make
> modifications to user (i.e. putting an user into another service's
> group to allow that user to access service in question) and it
> would be unexpected to see these changes reverted during normal
> world upgrade (which could break services).

It would be nice if this was well-supported by the official way of 
modifying system users/groups; that is, by using an overlay with 
modified user/group ebuilds.

Right now it's awkward to do because of the way the eclasses are 
structured. For example, some of our servers allow the "postfix" user to 
write to OpenDKIM's socket, but only on our *outgoing* mail servers (not 
on the incoming MX, where no signing takes place.) This is accomplished 
by creating an acct-group/dkimsocket ebuild (ok so far), and then by 
overriding the acct-user/postfix ebuild:

   EAPI=7

   inherit acct-user

   DESCRIPTION="user for postfix daemon"
   IUSE="dkimsocket"
   ACCT_USER_ID=207
   ACCT_USER_GROUPS=( postfix mail )
   acct-user_add_deps

   # This needs to be done outside of acct-user_add_deps because we can't
   # test use flags in global scope, and therefore we can't add groups
   # to ACCT_USER_GROUPS before calling acct-user_add_deps.
   RDEPEND+=" dkimsocket? ( acct-group/dkimsocket )"

   pkg_setup() {
       # https://wiki.gentoo.org/wiki/OpenDKIM
       #
       # Even though we added the group to RDEPEND manually, we still
       # need to add it to the array.
       if use dkimsocket; then
           ACCT_USER_GROUPS+=( dkimsocket )
       fi
   }

That's the common case of adding a system user to a group, and it's 
pretty ugly, so it's no wonder that people want to use "usermod" and 
then ignore subsequent changes by the PM.

And there's probably a backwards-compatible way we could support 
USE-conditional supplementary groups.