[blfs-dev] [lfs-dev] Glibc-2.18, pt_chown and terminal emulators

Bryan Kadzban bryan at kadzban.is-a-geek.net
Mon Aug 19 19:42:39 PDT 2013


Ragnar Thomsen wrote:
> In glibc 2.18, the pt_chown binary no longer gets installed by
> default due to security reasons. This resulted for me in konsole not
> working. I tracked the issue down to the missing pt_chown binary.

You shouldn't need pt_chown; devpts just needs to be mounted correctly.

> Instead I found that changing the gid of group tty to 5 fixed konsole
> (the tty group had a gid of 4 on my system).

That's old, see below.  On the other hand, I have gid=N in my fstab,
with N an integer, not a name.  On the other other hand, my fstab is
about four years old...

> It appears the gid of tty needs to be the same as the devpts
> filesystem is mounted with (which is 5 in LFS). This issue may also
> affect other terminal emulators.

The book assigns gid 5 to tty:

http://www.linuxfromscratch.org/lfs/view/development/chapter06/createfiles.html

...per Bruce's comment that "we changed that to 5 quite a while ago"
in the discussion of changing the chapter-6 devpts mount
(http://www.linuxfromscratch.org/lfs/view/development/chapter06/kernfs.html)
to provide -o gid=5 to get the glibc testsuite to work.  (I'd point to
the archives, but it seems they're 404, probably due to the server move.
I'm pretty sure it was less than a week ago though.)

See also:

http://www.linuxfromscratch.org/lfs/view/development/chapter08/fstab.html

where it's numeric, and 5.

> I suggest we add the tty group with gid 5 to the "About System Users 
> and Groups" in BLFS and maybe also add a note to the konsole page.

Not going to be just konsole; it'll affect any program that tries to
grantpt() as part of the PTY allocation handshake.  xterm, aterm, sshd,
expect, you name it.

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