Hi,
I know that LXC is not officially supported, but I still would like a to point out a change that causes problems on it.

I updated today (dockerized setup; ./update.sh), enabled Ipv6 and got this error when the stack was starting (this is a specific attempt, but the error was the same):

# docker-compose up -d redis-mailcow
Creating mailcow_redis-mailcow_1 ... error

ERROR: for mailcow_redis-mailcow_1  Cannot start service redis-mailcow: OCI runtime create failed: container_linux.go:380: starting container process caused: process_linux.go:545: container init caused: write sysctl key net.core.somaxconn: open /proc/sys/net/core/somaxconn: no such file or directory: unknown

ERROR: for redis-mailcow  Cannot start service redis-mailcow: OCI runtime create failed: container_linux.go:380: starting container process caused: process_linux.go:545: container init caused: write sysctl key net.core.somaxconn: open /proc/sys/net/core/somaxconn: no such file or directory: unknown
ERROR: Encountered errors while bringing up the project.

At first I thought that this is a fault of enabling ipv6 (it’s experimental BUT recommended?!?). After a lot of digging I found the culprit: The docker-compose now contains a setting for a sysctl:

    redis-mailcow:
      image: redis:6-alpine
      volumes:
        - redis-vol-1:/data/:Z
      restart: always
      ports:
        - "${REDIS_PORT:-127.0.0.1:7654}:6379"
      environment:
        - TZ=${TZ}
+      sysctls:
+        - net.core.somaxconn=4096
      networks:
        mailcow-network:
          ipv4_address: ${IPV4_NETWORK:-172.22.1}.249
          aliases:
            - redis

The problem is, that my host is running in an lxd container and this file isn’t available from within (the whole /proc/sys/net/core folder is actually empty). I had to comment this out for the time being.

The host has this already set to 4096 (but the lxd container can’t see that).

I’m running mailcow for about 1,5 years now (the server was even migrated 3 times and is now running almost a year in an lxc instance). So even if LXC/LXD isn’t officially supported. I’m happy to now start editing the docker-compose.yml after each update, but I just wanted to note that this change probably breaks some setups.