[systemd-devel] Mounting /dev/pts

Lennart Poettering lennart at poettering.net
Mon Jan 3 15:38:39 PST 2011

On Tue, 04.01.11 00:24, Wulf C. Krueger (philantrop at exherbo.org) wrote:

> Hello,
> currently, /dev/pts is mounted without the usual options by systemd.
> If /dev/pts is not mounted with the GID of the tty group, glibc (it assumes 
> tty as the group name, too) runs pt_chown which is generally undesirable since 
> it needs to be setuid (and is owned by root) and according to grantpt(3) "With 
> Linux devpts no such helper binary is required".
> Furthermore, having glibc run pt_chown effectively prevents strace -f'ing any 
> program that creates a pty (assuming it checks for errors properly), e. g. 
> strace -f urxvt.
> Setting mode=0620 should be done as well as it makes "mesg y" the default on 
> newly created PTYs (cf. mount(8)) which allows using write(1p).
> Both options are, to the best of my knowledge, commonly used among Linux 
> distros when mounting /dev/pts.
> I have tried to come up with a patch myself but failed disgracefully, I'm 
> afraid.

Normally, additional parameters listed in /etc/fstab should be applied
on boot with remount-api-vfs.service unit. However, there seems to be a
bug right now and this is not done properly.


Lennart Poettering - Red Hat, Inc.

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