gpg2 and gpg-agent (used by gnupg (1.x) as well) now uses
GPG_AGENT_INFO=/run/user/2339/gnupg/S.gpg-agent:0:1 but
the directory /run/user/2339 is removed on logout by elogind
even if processes are still running.

Unfortunately, this means gpg-agent kills itself when that
happens, e.g. when X crashes (Debian #912325) while, at the
same time, I’m logged in over ssh and working, e.g. in GNU
screen. This causes gnupg to completely fail (it asks for
the password, then tells me it cannot sign, breaking e.g.
signed git commits).

Furthermore, I’d prefer to move it to a location more easily
accessible in chroots, such as /dev/shm/ (see Debian #949698
where I’m already keeping my SSH agent information etc).

I’ve not found any elogind option to not remove that directory
on logout (as opposed to reboot which given it appears to be
a tmpfs is granted) and also suspect systemd behaves the same.

I happened to find a possible solution for this problem, if a user uses
systemd.

It seems that your use case is with elogind, so, this solution may not
work directly, but it would help seeking the way to solve.

In my system, I identified that:

The initial command creating /run/user/$UID/gnupg is this one (for
systemd users) by running gpgconf command:

    /lib/systemd/user-environment-generators/90gpg-agent

And then, this script also invokes gpgconf command:

    /etc/X11/Xsession.d/90gpg-agent

To introduce keeping old behavior of sockdir, I needed something
which runs before 90gpg-agent.

So, I created the file:
/etc/systemd/user-environment-generators/89-gpg-keep-old-behavior-of-sockdir-under-home

with the content of:
==========================
#!/bin/sh

D=/run/user/$(id -u)/
CONFIG_FILE=$HOME/.keep-old-behavior-of-gpg-sockdir

# Make a file to prevent use socketdir under /run by gnupg, but keep
# old behavior using $HOME/.gnupg
if [ -e $CONFIG_FILE ]; then
    touch ${D}/gnupg
fi
==========================

That is, when a user specified by the file of
$HOME/.keep-old-behavior-of-gpg-sockdir, it creates a file
'/run/user/$UID/gnupg' before the creation of directory
/run/user/$UID/gnupg, so that the directory cannot be created and used.

Then, by the fallback mechanism of GnuPG, $HOME/.gnupg will be used.

On Tue, 21 Dec 2021 15:17, NIIBE Yutaka said:

Another solution is to run

  touch /var/lib/elogin/linger/$(id -un)

once to more or less get standard Unix semantics back.


Shalom-Salam,

   Werner