bug#68255: 28.2; Can't connect to emacs daemon after logging out and back in.

bug#68255: 28.2; Can't connect to emacs daemon after logging out and back in.

[Jeremy Phelps]

1. Configure your session manager not to kill leftover user processes
   after logging out. If you're using elogind, this can be done by
   editing /etc/elogind/logind.conf and setting KillUserProcesses=no.
   Same process for systemd-logind, except the file is located
   at /etc/systemd/logind.conf.
2. Log into a new session and run "emacs --daemon".
3. Log out of all sessions for that user. This causes the directory
   named in $XDG_RUNTIME_DIR to be deleted, and with it, the Emacs
   daemon's socket.
4. Log back in.
5. Observe that the emacs daemon's process is still there, and that
   its socket is gone.

Working around this problem is difficult because the XDG_RUNTIME_DIR
variable whose use causes this problem is referenced in two places:

1. The "server-socket-dir" variable in Elisp. This is fairly easy to
   change because Emacs can take you right to the definition.
2. The emacsclient binary. Changing the behavior here requires
   editing emacsclient.c, recompiling, and installing the resulting
   binary. Except it's too hard to get Emacs to build on modern
   Linux distros, so I hex-edited the emacsclient binary instead,
   NUL-ing out all strings containing "XDG_RUNTIME_DIR".

In GNU Emacs 28.2 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.37,
cairo version 1.16.0)
 of 2023-05-13, modified by Debian built on x86-ubc-01
Windowing system distributor 'The X.Org Foundation', version 11.0.12101007
System Description: Devuan GNU/Linux 5 (daedalus)

Configured using:
 'configure --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/28.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/28.2/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils
 --with-native-compilation --build x86_64-linux-gnu --prefix=/usr
 --sharedstatedir=/var/lib --libexecdir=/usr/libexec
 --localstatedir=/var/lib --infodir=/usr/share/info
 --mandir=/usr/share/man --with-libsystemd --with-pop=yes
 --enable-locallisppath=/etc/emacs:/usr/local/share/emacs/28.2/site-lisp:/usr/local/share/emacs/site-lisp:/usr/share/emacs/28.2/site-lisp:/usr/share/emacs/site-lisp
 --with-sound=alsa --without-gconf --with-mailutils
 --with-native-compilation --with-cairo --with-x=yes
 --with-x-toolkit=gtk3 --with-toolkit-scroll-bars 'CFLAGS=-g -O2
 -ffile-prefix-map=/build/emacs-mPr7Vr/emacs-28.2+1=. -fstack-protector-strong
 -Wformat -Werror=format-security -Wall' 'CPPFLAGS=-Wdate-time
 -D_FORTIFY_SOURCE=2' LDFLAGS=-Wl,-z,relro'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GPM GSETTINGS HARFBUZZ JPEG
JSON LCMS2 LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 M17N_FLT MODULES
NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG RSVG SECCOMP SOUND THREADS TIFF
TOOLKIT_SCROLL_BARS X11 XDBE XIM XPM GTK3 ZLIB

Important settings:
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  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
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  global-eldoc-mode: t
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  auto-compression-mode: t
  line-number-mode: t
  indent-tabs-mode: t
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Load-path shadows:
/usr/share/emacs/site-lisp/elpa/slime-2.27/slime-tests hides
/usr/share/emacs/site-lisp/elpa-src/slime-2.27/slime-tests
/usr/share/emacs/site-lisp/elpa/slime-2.27/slime hides
/usr/share/emacs/site-lisp/elpa-src/slime-2.27/slime
/usr/share/emacs/site-lisp/elpa/slime-2.27/slime-pkg hides
/usr/share/emacs/site-lisp/elpa-src/slime-2.27/slime-pkg
/usr/share/emacs/site-lisp/elpa/slime-2.27/slime-autoloads hides
/usr/share/emacs/site-lisp/elpa-src/slime-2.27/slime-autoloads
/home/jlp/.emacs.d/elpa/transient-20200107.2156/transient hides
/usr/share/emacs/28.2/lisp/transient

Features:
(shadow sort mail-extr emacsbug message rmc puny dired dired-loaddefs
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org-footnote org-src ob-comint org-pcomplete pcomplete org-list
org-faces org-entities org-version ob-emacs-lisp ob-core ob-eval
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window text-properties overlay sha1 md5 base64 format env code-pages
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native-compile emacs)

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bug#68255: 28.2; Can't connect to emacs daemon after logging out and back in.

[Eli Zaretskii]

> From: Jeremy Phelps <jeremyphelps077@gmail.com>
> Date: Thu, 4 Jan 2024 14:52:17 -0500
> 
> 1. Configure your session manager not to kill leftover user processes
>    after logging out. If you're using elogind, this can be done by
>    editing /etc/elogind/logind.conf and setting KillUserProcesses=no.
>    Same process for systemd-logind, except the file is located
>    at /etc/systemd/logind.conf.
> 2. Log into a new session and run "emacs --daemon".
> 3. Log out of all sessions for that user. This causes the directory
>    named in $XDG_RUNTIME_DIR to be deleted, and with it, the Emacs
>    daemon's socket.
> 4. Log back in.
> 5. Observe that the emacs daemon's process is still there, and that
>    its socket is gone.
> 
> Working around this problem is difficult because the XDG_RUNTIME_DIR
> variable whose use causes this problem is referenced in two places:
> 
> 1. The "server-socket-dir" variable in Elisp. This is fairly easy to
>    change because Emacs can take you right to the definition.
> 2. The emacsclient binary. Changing the behavior here requires
>    editing emacsclient.c, recompiling, and installing the resulting
>    binary. Except it's too hard to get Emacs to build on modern
>    Linux distros, so I hex-edited the emacsclient binary instead,
>    NUL-ing out all strings containing "XDG_RUNTIME_DIR".

I'm not sure I understand why you cannot successfully use the daemon
in the situation you described.  Basically, what your scenario means
is that XDG_RUNTIME_DIR cannot be trusted because it is ephemeral, so
you need to tell Emacs and emacsclient to use a directory for a socket
in a way that doesn't use XDG_RUNTIME_DIR.  Is that correct?

If the above analysis is correct, then you can customize 'server-name'
to be an absolute file name of the directory where you want the socket
to be created, and invoke emacsclient with the --socket-name=NAME
option (or set EMACS_SOCKET_NAME=NAME in the environment), where NAME
is the same directory as in the value of 'server-name' option.  Did
you try that?

bug#68255: 28.2; Can't connect to emacs daemon after logging out and back in.

[Eli Zaretskii]

[Please use Reply All to reply, to keep the bug tracker CC'ed.]

> From: Jeremy Phelps <jeremyphelps077@gmail.com>
> Date: Fri, 5 Jan 2024 15:13:43 -0500
> 
> > If the above analysis is correct, then you can customize 'server-name'
> > to be an absolute file name of the directory where you want the socket
> > to be created, and invoke emacsclient with the --socket-name=NAME
> > option (or set EMACS_SOCKET_NAME=NAME in the environment), where NAME
> > is the same directory as in the value of 'server-name' option.  Did
> > you try that?
> 
> I did not try that, and I wouldn't be able to test it without reinstalling Emacs
> to get rid of my workaround.

Well, I'd encourage you to try this, because if it works, then there
is a solution to this situation, and if it doesn't work, we need to
fix whatever prevents it from working.

> But given that XDG_RUNTIME_DIR is ephemeral, and
> the Emacs daemon assumes it is not, it makes little sense to use it. It would
> make more sense to create a directory under ~/.emacs.d if security is the
> reason for using the XDG directory instead of /tmp.

I hear you, but other people disagree.  Some don't need to leave the
Emacs daemon running when they log off, and some say (AFAIU) that the
XDG directories don't get deleted when they log off.  So we support
both methods, and the XDG support takes precedence because most users
prefer it, AFAIU.

bug#68255: 28.2; Can't connect to emacs daemon after logging out and back in.

[Eli Zaretskii]

> Cc: 68255@debbugs.gnu.org
> Date: Sat, 06 Jan 2024 08:54:24 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
> [Please use Reply All to reply, to keep the bug tracker CC'ed.]
> 
> > From: Jeremy Phelps <jeremyphelps077@gmail.com>
> > Date: Fri, 5 Jan 2024 15:13:43 -0500
> > 
> > > If the above analysis is correct, then you can customize 'server-name'
> > > to be an absolute file name of the directory where you want the socket
> > > to be created, and invoke emacsclient with the --socket-name=NAME
> > > option (or set EMACS_SOCKET_NAME=NAME in the environment), where NAME
> > > is the same directory as in the value of 'server-name' option.  Did
> > > you try that?
> > 
> > I did not try that, and I wouldn't be able to test it without reinstalling Emacs
> > to get rid of my workaround.
> 
> Well, I'd encourage you to try this, because if it works, then there
> is a solution to this situation, and if it doesn't work, we need to
> fix whatever prevents it from working.

Any progress with this?

Thanks.

bug#68255: 28.2; Can't connect to emacs daemon after logging out and back in.

[Eli Zaretskii]

Ping! Could you please try the suggestion below, so we could make some
progress in handling this bug?  TIA.

> Cc: 68255@debbugs.gnu.org
> Date: Sun, 11 Feb 2024 10:50:27 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Cc: 68255@debbugs.gnu.org
> > Date: Sat, 06 Jan 2024 08:54:24 +0200
> > From: Eli Zaretskii <eliz@gnu.org>
> > 
> > [Please use Reply All to reply, to keep the bug tracker CC'ed.]
> > 
> > > From: Jeremy Phelps <jeremyphelps077@gmail.com>
> > > Date: Fri, 5 Jan 2024 15:13:43 -0500
> > > 
> > > > If the above analysis is correct, then you can customize 'server-name'
> > > > to be an absolute file name of the directory where you want the socket
> > > > to be created, and invoke emacsclient with the --socket-name=NAME
> > > > option (or set EMACS_SOCKET_NAME=NAME in the environment), where NAME
> > > > is the same directory as in the value of 'server-name' option.  Did
> > > > you try that?
> > > 
> > > I did not try that, and I wouldn't be able to test it without reinstalling Emacs
> > > to get rid of my workaround.
> > 
> > Well, I'd encourage you to try this, because if it works, then there
> > is a solution to this situation, and if it doesn't work, we need to
> > fix whatever prevents it from working.
> 
> Any progress with this?
> 
> Thanks.
> 
> 
> 
>