Forcing a different user and group in docker-compose results in tmp permission error on startup

[Undeadllama]

By default medaziz11/uptimekuma_restapi appears to run under uid 100.
This results in permissions errors on startup unless uid 100 has access to the /db volume.
sqlite3.OperationalError: unable to open database file

Giving the volume full 777 permissions allows for the sqlite db to be created, but under ownership of uid 100, which on my system is the default 'systemd-timesync' user:

dockeradmin@dockerhost:/dockershared/uptimekuma$ grep "x:100:" /etc/passwd
systemd-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/usr/sbin/nologin

dockeradmin@dockerhost:/dockershared/uptimekuma$ ll apidb
total 24
drwxrwxrwx 2 dockeradmin      docker           4096 Nov 30 22:07 ./
drwxr-xr-x 4 dockeradmin      docker           4096 Nov 30 22:08 ../
-rw-r--r-- 1 systemd-timesync systemd-journal 16384 Nov 30 22:07 db.sqlite3

This is not ideal so I attempted to force use of a different user by adding the following line to my docker-compose file:
user: 1000:1000

Which resulted in the following errors accessing /tmp when attempting to start up the container:

[2023-11-30 22:09:16 +0000] [1] [INFO] Unhandled exception in main loop
Traceback (most recent call last):
  File "/app/venv/lib/python3.9/site-packages/gunicorn/arbiter.py", line 202, in run
    self.manage_workers()
  File "/app/venv/lib/python3.9/site-packages/gunicorn/arbiter.py", line 551, in manage_workers
    self.spawn_workers()
  File "/app/venv/lib/python3.9/site-packages/gunicorn/arbiter.py", line 622, in spawn_workers
    self.spawn_worker()
  File "/app/venv/lib/python3.9/site-packages/gunicorn/arbiter.py", line 569, in spawn_worker
    worker = self.worker_class(self.worker_age, self.pid, self.LISTENERS,
  File "/app/venv/lib/python3.9/site-packages/uvicorn/workers.py", line 23, in __init__
    super(UvicornWorker, self).__init__(*args, **kwargs)
  File "/app/venv/lib/python3.9/site-packages/gunicorn/workers/base.py", line 64, in __init__
    self.tmp = WorkerTmp(cfg)
  File "/app/venv/lib/python3.9/site-packages/gunicorn/workers/workertmp.py", line 29, in __init__
    util.chown(name, cfg.uid, cfg.gid)
  File "/app/venv/lib/python3.9/site-packages/gunicorn/util.py", line 153, in chown
    os.chown(path, uid, gid)
PermissionError: [Errno 1] Operation not permitted: '/tmp/wgunicorn-nyytxa4w'

What is the correct method to change what user the container is running as if I want to avoid uid 100?

[hillout]

@Undeadllama I stumbled across the same problem. I think the best way to do it now is to rebuild the image with user you want.