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WSLg 做了什么(3)

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WSL2 without systemd

In miniwsl

  1. files
  $ ls -l /mnt/wslg/.X11-unix
  srwxrwxrwx    1 1000     1000             0 Apr 16 11:49 X0

  $ ls -l /mnt/wslg/runtime-dir
  drwx------    3 1000     1000            60 Apr 16 11:49 dbus-1
  drwx------    2 1000     1000            80 Apr 16 11:49 pulse
  srwxrwxrwx    1 1000     1000             0 Apr 16 11:49 wayland-0
  -rw-rw----    1 1000     1000             0 Apr 16 11:49 wayland-0.lock

  $ ls -l /mnt/wslg/runtime-dir/pulse
  srwxrwxrwx    1 1000     1000             0 Apr 16 11:49 native
  -rw-------    1 1000     1000             3 Apr 16 11:49 pid

  $ ls -l /mnt/wslg/PulseServer
  srwxrwxrwx    1 1000     1000             0 Apr 16 11:49 /mnt/wslg/PulseServer
  1. mount
  mount -o bind,ro /mnt/wslg/.X11-unix /tmp/.X11-unix
  1. env vars
  DISPLAY=:0
  XDG_RUNTIME_DIR=/mnt/wslg/runtime-dir
  WAYLAND_DISPLAY=wayland-0
  PULSE_SERVER=unix:/mnt/wslg/PulseServer

WSL2 with systemd

The above files, mounts and env vars without systemd, also exist in the distro like Ubuntu-22.04.

And there are more:

  1. files
  $ ls -l /mnt/wslg/run/user/1000
  drwxr-xr-x 3 user1 user1  60 Apr 16 19:30 dbus-1
  drwxr-xr-x 2 user1 user1  80 Apr 16 19:22 pulse
  lrwxrwxrwx 1 user1 user1  31 Apr 16 19:22 wayland-0 -> /mnt/wslg/runtime-dir/wayland-0
  lrwxrwxrwx 1 user1 user1  36 Apr 16 19:22 wayland-0.lock -> /mnt/wslg/runtime-dir/wayland-0.lock

  $ ls -l /mnt/wslg/run/user/1000/pulse
  lrwxrwxrwx 1 user1 user1 34 Apr 16 19:22 native -> /mnt/wslg/runtime-dir/pulse/native
  lrwxrwxrwx 1 user1 user1 31 Apr 16 19:22 pid -> /mnt/wslg/runtime-dir/pulse/pid
  1. mount
  mount -o bind /mnt/wslg/run/user /run/user
  1. env vars
  XDG_RUNTIME_DIR=/run/user/1000
  1. /tmp and /run/user/1000 are not mounted as tmpfs in Ubuntu-22.04
  $ mountpoint /tmp
  /tmp is not a mountpoint

  $ mountpoint /run/user/1000
  /run/user/1000 is not a mountpoint

We can see why /run/user/1000 is not mounted as tmpfs:

  $ systemctl status user-runtime-dir@1000
  systemd-user-runtime-dir[407]: Will mount /run/user/1000 owned by 1000:1000
  systemd-user-runtime-dir[407]: /run/user/1000 is already a mount point
  systemd[1]: Finished User Runtime Directory /run/user/1000.

It’s a bug in systemd-249 for Ubuntu-22.04 in /lib/systemd/systemd-user-runtime-dir:

  $ sudo mkdir /run/user/33
  $ sudo chgrp www-data /run/user/33
  $ sudo chown www-data /run/user/33

  $ ls -l /run/user
  total 0
  drwxr-xr-x 6 user1     user1     200 Apr 18 19:01 1000
  drwxr-xr-x 2 www-data  www-data   40 Apr 18 19:04 33

  $ sudo SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-user-runtime-dir start 33
  Will mount /run/user/33 owned by 33:33
  /run/user/33 is already a mount point

  $ sudo SYSTEMD_LOG_LEVEL=debug /lib/systemd/systemd-user-runtime-dir start 34
  Will mount /run/user/34 owned by 34:34
  Mounting tmpfs (tmpfs) on /run/user/34 (MS_NOSUID|MS_NODEV "mode=0700,uid=34,gid=34,size=1661825024,nr_inodes=405719")...

  $ ls -l /run/user
  total 0
  drwxr-xr-x 6 user1     user1     200 Apr 18 19:01 1000
  drwxr-xr-x 2 www-data  www-data   40 Apr 18 19:04 33
  drwx------ 2 backup    backup     40 Apr 18 19:09 34

  $ findmnt | grep run/user
  │ └─/mnt/wslg/run/user/34                               tmpfs                   tmpfs         rw,nosuid,nodev,relatime,size=1622876k,nr_inodes=405719,mode=700,uid=34,gid=34
  │ └─/run/user                                           none                    tmpfs         rw,nosuid,nodev,noexec,noatime,mode=755
  │   └─/run/user                                         none[/run/user]         tmpfs         rw,relatime
  │     └─/run/user/34                                    tmpfs                   tmpfs         rw,nosuid,nodev,relatime,size=1622876k,nr_inodes=405719,mode=700,uid=34,gid=34

WSL2 with systemd, but something goes wrong

  1. In arch there is /lib/systemd/system/tmp.mount,
    which do mount -t tmpfs tmpfs /tmp
  $ findmnt /tmp
  TARGET SOURCE FSTYPE OPTIONS
  /tmp   tmpfs  tmpfs  rw,nosuid,nodev,size=8114388k,nr_inodes=1048576

So, no /tmp/.X11-unix/X0, cause Error: Can't open display: :0.

Solutions:
1.1 disable tmp.mount by:

```sh
$ sudo systemctl mask tmp.mount
Created symlink /etc/systemd/system/tmp.mount → /dev/null.
```

1.2 or create links after /tmp mounted.

  1. In arch and Ubuntu-24.04, there are /usr/lib/systemd/system/user-runtime-dir@.service,
    which do mount -t tmpfs tmpfs /run/user/1000
  $ findmnt /run/user/1000
  TARGET         SOURCE FSTYPE OPTIONS
  /run/user/1000 tmpfs  tmpfs  rw,nosuid,nodev,relatime,size=1622876k,nr_inodes=405719,mode=700,uid=1000,gid=1000

So, no /run/user/1000/wayland-0 nor some other, cause Failed to create wl_display.

Solution is creating links after /run/user/1000/ mounted.