Subject: bug#74912: closed (Re: bug#76998: Guix Home leaves user shepherd on logout, starts new instance on login)

From: [email-masked] (GNU bug Tracking System)
Date: Sat, 14 Jun 2025 21:28:04 +0000

Your bug report

#76998: Guix Home leaves user shepherd on logout, starts new instance on login

which was filed against the guix package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
76998: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=76998
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#76998: Guix Home leaves user shepherd on logout, starts new instance on login
From: Ludovic Courtès <[email-masked]>
To: Danny Milosavljevic <[email-masked]>
Cc: [email-masked], [email-masked], Tomas Volf <[email-masked]>, [email-masked], Jake <[email-masked]>, Daniel Littlewood <[email-masked]>
Date: Sat, 14 Jun 2025 23:26:53 +0200
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi Danny,

Danny Milosavljevic <[email-masked]> writes:

> It's good that the "is a shepherd already running" check is back in
> shepherd.  It was in shepherd years ago, then got removed without
> explanation, then now it's back again (now in a very convoluted but
> safer way).  This shouldn't have been removed in the first place.
> It's EXTREMELY dangerous to have multiple parallel shepherds for the
> same user (automated backup service destroying backups etc).  Please,
> let's not remove it ever again.

If you’re referring to 649a98a6697d358a53eccc45b387e5130278b5ec (8 years
ago), I believe it wasn’t doing just that due to lingering.

(Aside: I think the tone of this paragraph is uncalled for.)

> In any case, what shepherd 1.0.4 does is stop the bleeding, but not fix the problem:
> It prevents two (or 100) user shepherds for the same user from running in parallel.
> It does not stop shepherd when a user closed all their sessions.

Yes.  It just occurred to me that we probably just got it wrong from the
start: ‘XDG_RUNTIME_DIR’ (/run/user/$UID) is specified as having limited
lifetime.  Quoth
<https://specifications.freedesktop.org/basedir-spec/latest/>:

  The lifetime of the directory MUST be bound to the user being logged
  in.  It MUST be created when the user first logs in and if the user
  fully logs out the directory MUST be removed.

So it was probably a bad idea in the first place for shepherd to store
its socket in /run/user/$UID (even more so that this directory doesn’t
exist on systems without elogind/systemd).  GnuPG avoids
$XDG_RUNTIME_DIR for exactly this reason (there’s a comment in
‘homedir.c’).

So, what can we do?

In the Shepherd 1.1, we could default to $XDG_STATE_HOME instead; we
probably shouldn’t change that in 1.0.x.

Any other idea?

Thanks,
Ludo’.

Subject: Shepherd: Growing number of user shepherds when relogging
From: Jake <[email-masked]>
To: [email-masked]
Cc: [email-masked]
Date: Mon, 16 Dec 2024 14:23:20 +0000
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi

I think I'm experiencing a bug in Shepherd since version 1.0.
Whenever I log out and log back in again, my user shepherd from the
previous login session is still present, and a new user shepherd spawns for
the current login session.
So relogging N times results in N+1 user shepherds.

For example, I have relogged 5 times since I last rebooted:

$ herd status root
Status of root:
  It is running since 00:30:02 (10 minutes ago).
  Main PID: 23450
  Command:
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
...

$ pgrep shepherd
1
9891
10777
16417
18510
21960
23450

$  ps aux | grep shepherd
root         1  0.0  0.9 222872 74456 ?        Sl   Dec15   0:08
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--config /gnu/store/p7al8wd1inwk8f5di2q4llcpd64mjn5q-shepherd.conf
jake      9891  0.0  0.2  75816 23624 ?        Ss   Dec15   0:04
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
jake     10777  0.0  0.3  76224 24752 ?        Ss   Dec16   0:03
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
jake     16417  0.0  0.3  75752 24004 ?        Ss   Dec16   0:02
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
jake     18510  0.0  0.2  75752 23760 ?        Ss   Dec16   0:01
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
jake     21960  0.0  0.2 114608 22124 ?        Ss   Dec16   0:00
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
jake     23450  0.0  0.2 114204 21328 ?        Ss   00:30   0:00
/gnu/store/mfkz7fvlfpv3ppwbkv0imb19nrf95akf-guile-3.0.9/bin/guile
--no-auto-compile
/gnu/store/nl0w5c7pxxdczqiv4r9iq44al7nd5y5g-shepherd-1.0.0/bin/shepherd
--silent --config /gnu/store/w3l6dmap815mm3qzx77xdazky853adda-shepherd.conf
jake     23672  0.0  0.0   6636  2552 pts/1    S+   00:32   0:00 grep
--color=auto shepherd

In addition, any daemons managed by the zombie shepherds also persist!

I'm experiencing this on both of my Guix System machines. One is running
GDM and XFCE. The other is running GDM and CWM.
Please let me know if I can provide more information.

Thanks
Jake