Context

Today I upgraded my host system (it's an Arch Linux on ARM64 RPi3), it upgraded the kernel (to 5.5.6) and other stuff, this generally has not been an issue at all, but today after that I couldn't start the docker-mailserver anymore, it exits with this error:

❯ sudo docker logs mail -f
Traceback (most recent call last):
  File "/usr/bin/supervisord", line 11, in <module>
    load_entry_point('supervisor==3.3.1', 'console_scripts', 'supervisord')()
  File "/usr/lib/python2.7/dist-packages/supervisor/supervisord.py", line 365, in main
    go(options)
  File "/usr/lib/python2.7/dist-packages/supervisor/supervisord.py", line 375, in go
    d.main()
  File "/usr/lib/python2.7/dist-packages/supervisor/supervisord.py", line 70, in main
    rlimit_messages = self.options.set_rlimits()
  File "/usr/lib/python2.7/dist-packages/supervisor/options.py", line 1372, in set_rlimits
    soft, hard = resource.getrlimit(res)
resource.error: (1, 'Operation not permitted')

I tried to add - ALL, - SYS_RESOURCE, etc to cap_add in docker-compose.yml, to check whether it was due to any new capability I needed to list, but it didn't help.

Expected Behavior

The container to start.

Actual Behavior

Container doesn't start due to permission error with getrlimit for RLIMIT_NOFILE.

Steps to Reproduce

1. Have host system as Arch Linux on ARM
2. Upgrade
3. Run docker-mailserver built from master

Your Environment

• Amount of RAM available: 1GB
• Mailserver version used: built from master
• Docker version used: 1:19.03.6-1
• Environment settings relevant to the config:
• Any relevant stack traces ("Full trace" preferred):