How to run a GUI application as a different user?

run-gui-apps-from-a-different-user.md

How to run a GUI application as a different user:

Suppose you are logged into your Linux box as user1 using some X window system already (with GNOME/Unity/..). Now you want to run some gui app as another user, user2.

Run:

1. xhost + - Run as the user1. This enables access to user1's X window system from other users. You should see following output: 'access control disabled, clients can connect from any host'
2. sudo su - user2 - Using your favorite terminal, log-in to second user.
3. export DISPLAY=:0.0 - optional for some apps.
4. # sudo mount --bind /home/user1 /home/user2 - optional. This mounts the /home/user1 dir into /home/user2. This is useful if you want to reuse user1's application configs. This can break some other apps sometimes, so only do this if this is really necessary. You can unmount at the end via sudo umount /home/user2.
5. execute the gui command:

firefox

I wrote ego (Alter Ego) for this use case, it automatically handles xhost and Wayland and PulseAudio socket sharing: https://github.com/intgr/ego

So you just run ego firefox or ego -u user2 firefox

If you run into problems, please open an issue on GitHub. I may be the only user of it, so it hasn't gotten much testing yet.

hey this works for some apps but for example FL Studio through Lutris doesnt work, ALSA throws errors

ALSA lib confmisc.c:855:(parse_card) cannot find card '0'
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_card_inum returned error: No such file or directory
ALSA lib confmisc.c:422:(snd_func_concat) error evaluating strings
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1334:(snd_func_refer) error evaluating name
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5701:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM sysdefault
ALSA lib confmisc.c:855:(parse_card) cannot find card '0'
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_card_inum returned error: No such file or directory
ALSA lib confmisc.c:422:(snd_func_concat) error evaluating strings
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1334:(snd_func_refer) error evaluating name
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5701:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM sysdefault
ALSA lib seq_hw.c:466:(snd_seq_hw_open) open /dev/snd/seq failed: Permission denied

do you know how to fix this? @kasunbg

Hey, thanks for this. Instead of xhost +, which disables access control (clients can connect from any host), I would recommend using xhost +SI:localuser:user2. And personally, instead of sudo su - user2, I prefer using plain su user2, which asks for user2's password instead of my own one.

But I'm happy that it works!

hey this works for some apps but for example FL Studio through Lutris doesnt work, ALSA throws errors

ALSA lib confmisc.c:855:(parse_card) cannot find card '0'
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_card_inum returned error: No such file or directory
ALSA lib confmisc.c:422:(snd_func_concat) error evaluating strings
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1334:(snd_func_refer) error evaluating name
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5701:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM sysdefault
ALSA lib confmisc.c:855:(parse_card) cannot find card '0'
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_card_inum returned error: No such file or directory
ALSA lib confmisc.c:422:(snd_func_concat) error evaluating strings
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_concat returned error: No such file or directory
ALSA lib confmisc.c:1334:(snd_func_refer) error evaluating name
ALSA lib conf.c:5178:(_snd_config_evaluate) function snd_func_refer returned error: No such file or directory
ALSA lib conf.c:5701:(snd_config_expand) Evaluate error: No such file or directory
ALSA lib pcm.c:2664:(snd_pcm_open_noupdate) Unknown PCM sysdefault
ALSA lib seq_hw.c:466:(snd_seq_hw_open) open /dev/snd/seq failed: Permission denied

do you know how to fix this? @kasunbg

Tried this with Spotify:

Be sure to add your user to the audio group before using su
sudo usermod -G audio -a user2

su user2

Then, as the substituted user,

• unset XDG_RUNTIME_DIR would be smart, to prevent writing to the wrong home directories, as some GUI apps will use this variable.
• Run an app that uses audio

Let me know if it works for you