Re: [HTCondor-users] Incompatibility of HTCondor "condor_ssh_to_job" with Apptainer 1.3.0?

[Dave Dykstra <dwd@xxxxxxxx>]

Nevermind, I was glossing over the deeper debugging you had done in condor, where you found the error being with /dev/ptmx.  According to strace nsenter does nothing with /dev/ptmx.  So I'd still like to know if condor_ssh_to_job works with apptainer-1.3.0 on EL9.

Dave

On Tue, Mar 26, 2024 at 09:26:50AM -0500, Dave Dykstra wrote:
> I have an nsenter script that includes using the "-r" option.  That gets an error on EL7 with apptainer-1.3.0 using fuse-overlayfs:
>     nsenter: cannot open /proc/1978437/root: Permission denied
> 
> If I remove the "-r" option, it works, and it works even with the -r option on EL9 with apptainer-1.3.0 using kernel overlayfs.
> 
> Do you see the same, Oliver?  Perhaps condor_ssh_to_job is using the "-r" option or its equivalent, and the error isn't getting passed along.  It's not clear to me that the option is doing anything useful; I'm not sure why I had it included in my script.
> 
> Dave
> 
> On Tue, Mar 26, 2024 at 09:05:07AM -0500, Dave Dykstra wrote:
> > Hi Oliver,
> > 
> > Does it happen also with an EL8 or EL9 host?  That uses kernel overlayfs instead of fuse-overlayfs.  I wonder if that makes a difference.
> > 
> > Dave
> > 
> > On Mon, Mar 25, 2024 at 10:31:20PM +0100, Oliver Freyermuth wrote:
> > > Dear HTCondor experts (probably Greg â hello from Bonn! ;-) ),
> > > 
> > > I finally came around upgrading a first system to Apptainer 1.3.0, which now uses fuse-overlayfs by default instead of the previous "underlay" approach which is going to be deprecated in a future release.
> > > 
> > > Trying to start an interactive job (or connecting to an existing job) now reveals (note: we run Apptainer unprivilegedly):
> > > ...
> > >   Your condor job is running with pid(s) 34563.
> > >   Can't open master pty Bad file descriptor
> > >   read returned, exiting
> > > ...
> > > 
> > > 
> > > I can pin this down to the following problem:
> > > 
> > > 
> > > 1) Process tree:
> > > 
> > > condor    34472  1.7  0.0  91048  8624 ?        Ss   22:18   0:00      \_ condor_starter -f -local-name slot_type_1 -a slot1_2 exp196.physik.uni-bonn.de
> > > freyermu  34563  2.5  0.0 963708 19548 ?        SNsl 22:18   0:00          \_ Apptainer runtime parent
> > > freyermu  34587  0.0  0.0 888016 17256 ?        SNl  22:18   0:00              \_ appinit
> > > freyermu  34622  0.0  0.0   3800  1376 ?        SN   22:18   0:00              |   \_ /bin/sh -c sleep 180 && while test -d ${_CONDOR_SCRATCH_DIR}/.condor_ssh_to_job_1; do /bin/sleep 3; done
> > > freyermu  34623  0.0  0.0   2376   364 ?        SN   22:18   0:00              |       \_ sleep 180
> > > freyermu  34606  1.5  0.0  16200  3092 ?        SN   22:18   0:00              \_ /usr/libexec/apptainer/bin/fuse-overlayfs -f -o allow_other,lowerdir=/var/lib/apptainer/mnt/session/overlay-lowerdir:/var/lib/apptainer/mnt/session/rootfs...
> > > 
> > > 
> > > 2) Running the following (using any PID "deeper" down, e.g. 34622 or 34623, does the same)
> > >      strace -f condor_nsenter -t 34587 -S <my_id> -G <_my_gid>
> > >     reveals:
> > >      open("/proc/34587/ns/uts", O_RDONLY)    = 3
> > >      setns(3, 0)                             = 0
> > >      close(3)                                = 0
> > >      open("/proc/34587/ns/pid", O_RDONLY)    = 3
> > >      setns(3, 0)                             = 0
> > >      close(3)                                = 0
> > >      open("/proc/34587/ns/mnt", O_RDONLY)    = 3
> > >      setns(3, 0)                             = 0
> > >      close(3)                                = 0
> > >      setgroups(0, NULL)                      = 0
> > >      setgid(513)                             = 0
> > >      setuid(67803)                           = 0
> > >      ioctl(0, TIOCGWINSZ, {ws_row=58, ws_col=236, ws_xpixel=1891, ws_ypixel=988}) = 0
> > >      open("/dev/ptmx", O_RDWR)               = -1 EACCES (Permission denied)
> > >      ioctl(-1, TIOCSPTLCK, [0])              = -1 EBADF (Bad file descriptor)
> > >      write(2, "Can't open master pty Bad file d"..., 42Can't open master pty Bad file descriptor
> > >      ) = 42
> > >      exit_group(1)                           = ?
> > >      +++ exited with 1 +++
> > > 
> > > I'm not sure what exactly makes the difference, but:
> > >   nsenter -t 34587 -U -m -p -S <my_id> -G <_my_gid>
> > > "works" and I can access /dev/ptmx inside.
> > > 
> > > SELinux is not at fault, no denials, and disabling it changes nothing.
> > > 
> > > Any ideas? Do others also see this issue?
> > > 
> > > Disabling fuse-overlayfs usage via the Apptainer configuration and forcing it back to use Underlay seems to fix the problem (enable overlay = no, enable underlay = yes),
> > > but the Apptainer guys want to remove that implementation at some point.
> > > 
> > > Cheers,
> > >         Oliver
> > > 
> > > --
> > > Oliver Freyermuth
> > > UniversitÃt Bonn
> > > Physikalisches Institut, Raum 1.047
> > > NuÃallee 12
> > > 53115 Bonn
> > > --
> > > Tel.: +49 228 73 2367
> > > Fax:  +49 228 73 7869
> > > --
> > 
> > 
> > 
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