Devuan 4.0 template and tmux - UNprivileged container failure with non-root user

[hvisage]

Good day,

I've been deploying Devuan 4.0 images (pve 7.4) the past 4 months, and had noticed `byobu` strangeness, but only this week it caused me problems that I had to get to the bottom of it.

I've tried all the settings in the GUI panel for UNprivileged containers, and eventually installed a privleged container where byobu-tmux works as a non-root user.

Today I've tried the Debian 11.7, Debian 12.0, and Ubuntu templates, and they all work fine.

The problem seems to be related to some permissions, as the strace shows the last message (whcih doesn't show on the terminal) something like `create window failed: fork failed`

the glaring things that pops up is access permissions on `/dev/ptmx` and
`connect(5, {sa_family=AF_UNIX, sun_path="/tmp/tmux-1000/default"}, 110) = -1 ECONNREFUSED (Connection refused)`

testing with screen & tmux alone, seems to have the same problem, they can't run as non-root users,


Any ideas where to check find the problem?

 

[hvisage]

Okay, seems to find the "culprit":
This is the values that is set inside the Devuan 4.0 container:

/proc/1/task/1/mounts:devpts /dev/pts devpts rw,nosuid,noexec,relatime,mode=600,ptmxmode=000 0 0

And for a Debian container:

devpts /dev/ptmx devpts rw,nosuid,noexec,relatime,gid=100005,mode=620,ptmxmode=666,max=1026 0 0

Seems this is related:
https://www.kernel.org/doc/Documentation/filesystems/devpts.txt

reading https://discuss.linuxcontainers.org/t/dev-ptmx-permission-issue/15509

the fix for Devuab 4.0 template seems to be to add this to /etc/fstabinside the container:

# UNCONFIGURED FSTAB FOR BASE SYSTEM
devpts /dev/pts devpts rw,nosuid,noexec,relatime,mode=620,ptmxmode=666,max=1026 0 0