[CRIU] two runc related questions (-d and read-only)

[Andrei Vagin]

On Mon, Sep 12, 2016 at 07:41:29PM +0200, Adrian Reber wrote:
> I was trying to checkpoint and restore a runc container and so far I had
> two smaller problems. My runc container has
> 
> 	"terminal": false
> 
> and I am starting it detached '-d'. Checkpointing this container fails
> if I run 'runc checkpoint --shell-job test' or without '--shell-job'
> with following error:
> 
> (00.003008) 29213 fdinfo 0: pos: 0x               0 flags: 102002/0
> (00.003022) tty: Dumping tty 8 with id 0x7
> (00.003026) Error (files-reg.c:1141): Can't lookup mount=22 for fd=0 path=/dev/pts/2
> (00.003029) ----------------------------------------
> (00.003071) Error (cr-dump.c:1296): Dump files (pid: 29213) failed with -1
> 
> I get the same error using criu-2.4 and latest master. If I start the
> container without '-d' I can checkpoint it without any problem.

Could you try to run ./runc ... &> /dev/null  < /dev/null? Will it help?

Could you show lsof -p for an init process of a container?

> 
> Another problem I have seen is using runc with
> 
> 	"readonly": true
> 
> this gives me following error:
> 
> (00.079785) Dumping task cwd id 0xb root id 0xb
> (00.079931) mnt: Dumping mountpoints
> (00.079934) mnt: 	213: 2b:/null @ ./proc/sched_debug
> (00.079934) mnt: Something is mounted on top of ./dev
> (00.080004) Error (criu/mount.c:1044): mnt: Can't create a temporary directory: Read-only file system

It's known issue. Yesterday I started to rework mount.c to support this
case. I will try to prepare draft patches before Friday.

Thanks,
Andrei

> 
> Starting the container with a read-write filesystem works.
> 
> I am curious why it fails for the detached and the read-only case. Is
> this something that can be fixed?
> 
> 		Adrian
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