Linux @lemmy.ml talkingpumpkin @lemmy.world 2mo ago

Do you know if it's possible to run a second session in a window?

I'm not much hoepful, but... just in case :)

I would like to be able to start a second session in a window of my current one (I mean a second session where I log in as a different user, similar to what happens with the various ctrl+alt+Fx, but starting a graphical session rather than a console one).

Do you know of some software that lets me do it?

Can I somehow run a KVM using my host disk as a the disk for the guest VM (and without breaking stuff)?

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32 comments

Totally possible. It'll work best with Wayland thanks to nested compositor support, whereas on Xorg you'd need to use Xephyr which doesn't do hardware acceleration.

# Give the other user access to your Wayland socket setfacl -m u:otheruser:rx $XDG_RUNTIME_DIR setfacl -m u:otheruser:rwx $XDG_RUNTIME_DIR/wayland-0 # Open a session as the other user (note the trailing @, it's there to login in to the local machine) sudo machinectl login otheruser@ # Start your DE! WAYLAND_DISPLAY=/run/user/$(id -u yourmainuser)/wayland-0 startplasma-wayland

And tada!
- Nice
- You can also nest rootful Xwayland in there too!
  
  From the user's shell,
  
  WAYLAND_DISPLAY=/run/user/1000/wayland-0 Xwayland :1 & export DISPLAY=:1 WAYLAND_DISPLAY= i3 & xterm & konsole &
  
  Of course you that means you can also run Plasma X11 that way for example:
- Wow, that's so neat!
  
  On my machine it opens a fullscreen plasma spash and then it shows the new session intermixed/overlayed with my current one instead of in a new window... basically, it's a mess :D
  
  If I may abuse your patience:
  
  what distro/plasma version are you running? (here it's opensuse slowroll w/ plasma 6.1.4)
  
  what happens if you just run startplasma-wayland from a terminal as your user? (I see the plasma splash screen and then I'm back to my old session)
  
  Make sure to use machinectl and not sudo or anything else. That's about the symptoms I'd expect from an incomplete session setup. The use of machinectl there was very deliberate, as it goes through all the PAM, logind, systemd and D-Bus stuff as any normal login. It gets you a clean and properly registered session, and also gets rid of anything tied to your regular user:
  
  max-p@desktop ~> loginctl list-sessions SESSION UID USER SEAT LEADER CLASS TTY IDLE SINCE 2 1000 max-p seat0 3088 user tty2 no - 3 1000 max-p - 3112 manager - no - 8 1001 tv - 589069 user pts/4 no - 9 1001 tv - 589073 manager - no -
  
  It basically gets you to a state of having properly logged into the system, as if you logged in from SDDM or in a virtual console. From there, if you actually had just logged in a tty as that user, you could run startplasma-wayland and end up in just as if you had logged in with SDDM, that's what SDDM eventually launches after logging you in, as per the session file:
  
  max-p@desktop ~> cat /usr/share/wayland-sessions/plasma.desktop [Desktop Entry] Exec=/usr/lib/plasma-dbus-run-session-if-needed /usr/bin/startplasma-wayland TryExec=/usr/bin/startplasma-wayland DesktopNames=KDE Name=Plasma (Wayland) # ... and translations in every languages
  
  From there we need one last trick, it's to get KWin to start nested. That's what the additional WAYLAND_DISPLAY=/run/user/1000/wayland-0 before is supposed to do. Make sure that this one is ran within the machinectl shell, as that shell and only that shell is the session leader.
  
  The possible gotcha I see with this, is if startplasma-wayland doesn't replace that WAYLAND_DISPLAY environment variable with KWin's, so all the applications from that session ends up using the main user. You can confirm this particular edge case by logging in with the secondary user on a tty, and running the same command including the WAYLAND_DISPLAY part of it. If it starts and all the windows pop up on your primary user's session, that's the problem. If it doesn't, then you have incorrect session setup and stuff from your primary user bled in.
  
  Like, that part is really important, by using machinectl the process tree for the secondary user starts from PID 1:
  
  max-p@desktop ~> pstree systemd─┬─auditd───{auditd} ├─bash─┬─(sd-pam) # <--- This is the process machinectl spawned │ └─fish───zsh───fish───zsh # <-- Here I launched a bunch of shells to verify it's my machinectl shell ├─systemd─┬─(sd-pam) # <-- And that's my regular user │ ├─Discord─┬─Discord───Discord───46*[{Discord}] │ ├─DiscoverNotifie───9*[{DiscoverNotifie}] │ ├─cool-retro-term─┬─fish───btop───{btop} │ ├─dbus-broker-lau───dbus-broker │ ├─dconf-service───3*[{dconf-service}] │ ├─easyeffects───11*[{easyeffects}] │ ├─firefox─┬─3*[Isolated Web Co───30*[{Isolated Web Co}]]
  
  Super weird stuff happens otherwise that I can't explain other than some systemd PAM voodoo happens. There's a lot of things that happens when you log in, for example giving your user access to keyboard, mouse and GPU, and the type of session depends on the point of entry. Obviously if you log in over SSH you don't get the keyboard assigned to you. When you switch TTY, systemd-logind also moves access to peripherals such that user A can't keylog user B while A's session is in the background. Make sure the machinectl session is also the only session opened for the secondary user, as it being assigned to a TTY session could also potentially interfere.
  
  what distro/plasma version are you running? (here it's opensuse slowroll w/ plasma 6.1.4)
  
  Arch, Plasma 6.1.5.
  
  what happens if you just run startplasma-wayland from a terminal as your user? (I see the plasma splash screen and then I'm back to my old session)
  
  You mean a tty or a terminal emulator like Konsole?
  
  In a tty
  
  if I'm already logged in it should switch to the current session as multi-instance is not supported
  
  if it's my only graphical session, it should start Plasma normally with the only exception being KWallet not unlocking automatically.
  
  In a terminal within my graphical session: nothing at all.
  
  Screenshot of said mess? Purley for entertainment 😄
  
  I fear it was nothing that entertaining: it was just my "normal" dark panel at the top of the screen and a second "default" white one at the bottom (this last one partially covered the windows I had open). I didn't try triggering notifications or otherwise causing some kind of mayhem.
- This looks so neat, I screenshot for future reference if I wanted to recreate this, thanks :)
  
  You can also bookmark comments on Lemmy, and copy the comment URL and store that in (synced) browser bookmarks!
  
  Oh, copy the comment text and save it in a text- or markdown-file on your devices, in case it gets taken down! You can even for the text in case you forgot where you kept it!
- Start your DE!
  
  WAYLAND_DISPLAY=/run/user/$(id -u yourmainuser)/wayland-0 startplasma-wayland
  
  This is cool

32 comments