Re: [PATCH RFC] util: pick a better runtime directory when XDG_RUNTIME_DIR isn't set

On Tue, Feb 18, 2025 at 09:33:43AM -0500, Laine Stump wrote: > On 2/18/25 4:26 AM, Daniel P. Berrangé wrote: > > On Mon, Feb 17, 2025 at 03:11:56PM -0500, Laine Stump wrote: > > > On 2/17/25 5:28 AM, Daniel P. Berrangé wrote: > > > > On Mon, Feb 17, 2025 at 02:14:49AM -0500, Laine Stump wrote: > > > > > But sometimes XDG_RUNTIME_DIR isn't set in the user's environment. > > > > > > > > Do you have examples of scenarios in which this happens, and > > > > yet the /run/user/NNNN directory is still being created, as > > > > that rather sounds like something is broken outside of libvirt. > > > > > > After seeing the bug report, I replicated the situation by ssh'ing in as a > > > user that hadn't previously logged in, and then unsetting XDG_RUNTIME_DIR. I > > > hadn't thought there might be some other case where the user could be logged > > > in but XDG_RUNTIME_DIR had never been set. > > > > > > But after seeing your question I tried running > > > > > > sudo $someuser virsh list > > > > NB, that is the classic sudo usage trapdoor, because they didn't > > make "-i" (aka --login) the default, so your environment is not > > populated correctly. > > > > I'd hope that when passing sudo -i ... it will do the right > > thing > > It seems not. If I login as $someuser, start a guest, then in a separate > terminal window from root run: > > sudo -u $someuser -i virsh list > > It returns an empty list (the same as if I omit the -i). By running the same > command without "virsh list", I'm given a shell instance, and within that > shell I can see that $UID, $USER, and $EUID are all set, but > $XDG_RUNTIME_DIR is not. Hmm, this appears to be caused by systemd_pam When using "su -" (similar seen with sudo) su[5870]: pam_systemd(su-l:session): pam-systemd initializing su[5870]: pam_systemd(su-l:session): New sd-bus connection (system-bus-pam-systemd-5870) opened. su[5870]: pam_systemd(su-l:session): Asking logind to create session: uid=1001 pid=5870 service=su-l type=tty class=user desktop= seat= vtnr=0 tty=pts/3 display= remote=no remote_user=root remote_host= su[5870]: pam_systemd(su-l:session): Session limits: memory_max=n/a tasks_max=n/a cpu_weight=n/a io_weight=n/a runtime_max_sec=n/a su[5870]: pam_systemd(su-l:session): Not creating session: Already running in a session or user slice su[5870]: pam_systemd(su-l:session): pam-systemd shutting down vs used with ssh: sshd-session[5937]: pam_systemd(sshd:session): pam-systemd initializing sshd-session[5937]: pam_systemd(sshd:session): New sd-bus connection (system-bus-pam-systemd-5937) opened. sshd-session[5937]: pam_systemd(sshd:session): Asking logind to create session: uid=0 pid=5937 service=sshd type=tty class=user desktop= seat= vtnr=0 tty= display= remote=yes remote_user= remote_host=10.42.28.158 sshd-session[5937]: pam_systemd(sshd:session): Session limits: memory_max=n/a tasks_max=n/a cpu_weight=n/a io_weight=n/a runtime_max_sec=n/a sshd-session[5937]: pam_systemd(sshd:session): Reply from logind: id=12 object_path=/org/freedesktop/login1/session/_312 runtime_path=/run/user/0 session_fd=9 seat= vtnr=0 original_uid=0 So if the current user is already in a login sesssion, it'll refuse to start a new session. I struggle to understand the rationale for this behaviour. It seems guaranteed to break stuff...