Luciano Mannucci wrote:
> I have two Beowulf systems that should be identical. If I issue "df"
> one does report among mounted filesystems a /run/user/xxx, where xxx
> is the id number of the user I am connected with (via ssh) and the
> other doesn't. As uname -a they both report:

I also don't desire that configuration and so also remove it from my
system. But I automate this and have for so long that I have
forgotten the root of it. But I believe this is due to the action of
PAM (Plugable Authentication Modules) which connect login session
accounts to libpam-systemd. Or at least it did at one time. IIRC.

Compare the contents of /etc/pamd.d on the two of your systems and see
what is different about them. The one with /run/user will have PAM
modules that the one without does not have. Pretty sure. I think.

If it were me I would copy the /etc/pam.d of one system to the other
and then diff the two.

    rsync -av othersystem:/etc/pam.d /tmp/junk/
    diff -ru /tmp/junk/pam.d/ /etc/pam.d/

My old private notes from Stretch or around then say this following.
These are old notes and package names have mutated since then.

    # File /etc/pam.d/common-session is modified by libpam-systemd
    # postinst script to add the following line.
    #   session  optional        pam_systemd.so
    # See man pam_systemd(8) for more details.
    # Note: pam_systemd.so creates /run/user/$(id -u) files.

Also my problem at the time was that X would not start with this PAM
configuration in place and I needed to remove it in order to get X to
start. Because it needed all of the rest of systemd installed and of
course I didn't have it installed. Therefore I needed to remove it.
But in Devuan elogind has replaced logind in order to address this.

I expect that your system with /run/user has a configuration like this
that your system that does not have /run/user does not have.

Caution: I am not really up to date on the current state of things
here. I am just pretty sure that that the /run/user stuff is
configured through PAM and is set up through elogind/logind through
the /etc/pam.d/* interface somewhere. I remove those entry lines from
pam.d files and it avoids that configuration.

Also starting X can be related and I have xserver-xorg-legacy
installed. I would also cross-check whether it is installed and on
which ones of your two systems.

Bob