[CRIU] PID mismatch problem

[Pavel Emelyanov]

On 12/22/2015 01:37 PM, Federico Reghenzani wrote:
> Ok, I'm trying to restore in a new namespace (I would prefer this solution to start the
> orted directly in a dedicated namespace), but I can't do it with C API.

Well, yes, the C API is not yet up to this.

You can try to call unshare() glibc function by hands before fork()-ing and 
exec()-ing criu. This would be good approximation of what my --unshare patchset
does. Or pick one up and add respective calls to lib/criu.c, this contribution
will be accepted with gratitude :)

> From command line via ssh:
> 
> ssh root at 10.10.1.2 <mailto:root at 10.10.1.2> unshare -p --fork criu restore -D /tmp/ckpt_B2BLJ
> 
> it works (even if it provides some error messages), but using orted-restore in C API:
> 
>     unshare(CLONE_NEWPID);
>     if (pid != 0) {
>          ...
>     }
>     // getpid == 1 now
>     dir = ...
>     criu_init_opts();
>     criu_set_images_dir_fd(dir);
>     criu_set_log_file("criu_restore.log");
>     criu_set_log_level(4);
>     int status = criu_restore_child();
> //or int status = criu_restore();
> 
> I obtain:
> 
>     Error (image.c:405): Can't open dir /proc/1/fd/11: No such device or address

That's because you only spawned new pid namespace, but the /proc remained the same
showing pids from wrong (previous) namespace. If you use -m and --mount-proc that
would help.

>     Error (cr-service.c:254): Can't open images directory: No such device or address
> 
> I've never used unshare, so I probably missed something ;-)
> 
> ----
> 
> P.S. the tty problem happens only when I open an ssh session and then execute the command (sshd: root at pts/0), no problem if I call criu restore directly from ssh command (sshd: root at notty).
> 
> Cheers,
> Federico
> __
> Federico Reghenzani
> M.Eng. Student @ Politecnico di Milano
> Computer Science and Engineering

-- Pavel