Hello,
I’ve run into a problem with /dev/ptmx file in a privileged Alt Linux container.
/dev/ptmx has 000 permissions and because of it, user processes can’t create ptys:
c--------- 1 root root 5, 2 Oct 31 14:15 /dev/ptmx
The problem goes away if I change permissions to 666 manually but it’s 000 again on the next container’s start.
Here’re the permissions and mounts inside the container:
[root@container ~]# ls -l /dev/pts/ptmx /dev/ptmx
c--------- 1 root root 5, 2 Oct 31 14:18 /dev/ptmx
c--------- 1 root root 5, 2 Oct 31 14:18 /dev/pts/ptmx
[root@container ~]# mount|grep pts
devpts on /dev/lxc/console type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/console type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/ptmx type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/lxc/tty1 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/lxc/tty2 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/lxc/tty3 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/lxc/tty4 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
Same on the host:
[root@host ~]# ls -l /dev/pts/ptmx /dev/ptmx
crw-rw-rw- 1 root tty 5, 2 окт 31 14:20 /dev/ptmx
c--------- 1 root root 5, 2 окт 31 13:41 /dev/pts/ptmx
[root@host ~]# mount|grep pts
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
I also checked permissions in Ubuntu 20.04 container where everything works fine:
mva@ubuntu:~$ ls -l /dev/pts/ptmx /dev/ptmx
crw-rw-rw- 1 root root 5, 2 окт 31 14:21 /dev/ptmx
crw-rw-rw- 1 root root 5, 2 окт 31 14:21 /dev/pts/ptmx
mva@ubuntu:~$ mount|grep pts
devpts on /dev/lxc/console type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/console type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666,max=1024)
devpts on /dev/ptmx type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666,max=1024)
devpts on /dev/lxc/tty1 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666,max=1024)
devpts on /dev/lxc/tty2 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666,max=1024)
devpts on /dev/lxc/tty3 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666,max=1024)
devpts on /dev/lxc/tty4 type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=666,max=1024)
It seems the problem is in ptmxmode option? How can I fix it?