Re: [Announce] Checkpoint-restore tool v0.1

Re: [Announce] Checkpoint-restore tool v0.1

[Pavel Emelyanov]

Fixing the bogus containers@ ml and adding cgroups@ one. Sorry :(

== Original message ==

Hi!

I'm glad to announce the first release of the checkpoint-restore tool.


This project is an attempt to implement the checkpoint-restore functionality
for processes and containers without driving too much code into the kernel tree,
but putting there "various oddball helper code" instead.

The tool can already be used for checkpointing and restoring various individual
applications. And the greatest thing about this so far is that most of the below
functionality has the required kernel support in the recently released v3.5!

So, we support now

* x86_64 architecture
* process' linkage
* process groups and sessions (without ttys though :\ )
* memory mappings of any kind (shared, file, etc.)
* threads
* open files (shared between tasks and partially opened-and-unlinked)
* pipes and fifos with data
* unix sockets with packet queues contents
* TCP and UDP sockets (TCP connections support exists, but needs polishing)
* inotifies, eventpoll and eventfd
* tasks' sigactions setup, credentials and itimers
* IPC, mount and PID namespaces

Though namespaces support is in there, we do not yet support an LXC container c/r,
but we're close to it :)


I'd like to thank everyone who took part in new kernel APIs discussions, the
feedback was great! Special thanks goes to Linus for letting the kernel parts
in early, instead of making them sit out of tree till becoming stable enough.


Tarball with the tool sources is at

  http://download.openvz.org/criu/crtools-0.1.tar.bz2

The git repo is at

  http://git.criu.org/

And some sort of docs growing at

  http://criu.org/


There are still things for which we don't have the kernel support merged (SysVIPC
and various anon file descriptors, i.e. inotify, eventpoll, eventfd) yet. We have
the kernel branch with the stuff applied available at

  https://github.com/cyrillos/linux-2.6.git


Thanks,
Pavel

Re: [Announce] Checkpoint-restore tool v0.1

[Serge Hallyn]

Quoting Pavel Emelyanov (xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org):
> Fixing the bogus containers@ ml and adding cgroups@ one. Sorry :(
> 
> == Original message ==
> 
> Hi!
> 
> I'm glad to announce the first release of the checkpoint-restore tool.
> 
> 
> This project is an attempt to implement the checkpoint-restore functionality
> for processes and containers without driving too much code into the kernel tree,
> but putting there "various oddball helper code" instead.
> 
> The tool can already be used for checkpointing and restoring various individual
> applications. And the greatest thing about this so far is that most of the below
> functionality has the required kernel support in the recently released v3.5!
> 
> So, we support now
> 
> * x86_64 architecture
> * process' linkage
> * process groups and sessions (without ttys though :\ )
> * memory mappings of any kind (shared, file, etc.)
> * threads
> * open files (shared between tasks and partially opened-and-unlinked)
> * pipes and fifos with data
> * unix sockets with packet queues contents
> * TCP and UDP sockets (TCP connections support exists, but needs polishing)
> * inotifies, eventpoll and eventfd
> * tasks' sigactions setup, credentials and itimers
> * IPC, mount and PID namespaces
> 
> Though namespaces support is in there, we do not yet support an LXC container c/r,
> but we're close to it :)
> 
> 
> I'd like to thank everyone who took part in new kernel APIs discussions, the
> feedback was great! Special thanks goes to Linus for letting the kernel parts
> in early, instead of making them sit out of tree till becoming stable enough.
> 
> 
> Tarball with the tool sources is at
> 
>   http://download.openvz.org/criu/crtools-0.1.tar.bz2
> 
> The git repo is at
> 
>   http://git.criu.org/
> 
> And some sort of docs growing at
> 
>   http://criu.org/
> 
> 
> There are still things for which we don't have the kernel support merged (SysVIPC
> and various anon file descriptors, i.e. inotify, eventpoll, eventfd) yet. We have
> the kernel branch with the stuff applied available at
> 
>   https://github.com/cyrillos/linux-2.6.git
> 
> 
> Thanks,
> Pavel

Awesome - thanks, Pavel, and congratulations :)  I'll have to give it a
spin as soon as I get a chance.

Re: [Announce] Checkpoint-restore tool v0.1

[richard -rw- weinberger]

On Mon, Jul 23, 2012 at 10:53 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
> This project is an attempt to implement the checkpoint-restore functionality
> for processes and containers without driving too much code into the kernel tree,
> but putting there "various oddball helper code" instead.

Is CRIU able to checkpoint a process tree where one or more processes
are traced using ptrace()?
crtools seem to use ptrace() to execute parasite system calls.
AFAIK this will only work if the target process is currently not
ptraced() by another process.

-- 
Thanks,
//richard

Re: [Announce] Checkpoint-restore tool v0.1

[Pavel Emelyanov]

On 07/30/2012 02:42 PM, richard -rw- weinberger wrote:
> On Mon, Jul 23, 2012 at 10:53 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>> This project is an attempt to implement the checkpoint-restore functionality
>> for processes and containers without driving too much code into the kernel tree,
>> but putting there "various oddball helper code" instead.
> 
> Is CRIU able to checkpoint a process tree where one or more processes
> are traced using ptrace()?

No it's not (currently).

> crtools seem to use ptrace() to execute parasite system calls.
> AFAIK this will only work if the target process is currently not
> ptraced() by another process.
> 

Yup, exactly.

Thanks,
Pavel

Re: [Announce] Checkpoint-restore tool v0.1

[richard -rw- weinberger]

On Tue, Jul 31, 2012 at 10:53 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
> On 07/30/2012 02:42 PM, richard -rw- weinberger wrote:
>> On Mon, Jul 23, 2012 at 10:53 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>>> This project is an attempt to implement the checkpoint-restore functionality
>>> for processes and containers without driving too much code into the kernel tree,
>>> but putting there "various oddball helper code" instead.
>>
>> Is CRIU able to checkpoint a process tree where one or more processes
>> are traced using ptrace()?
>
> No it's not (currently).
>
>> crtools seem to use ptrace() to execute parasite system calls.
>> AFAIK this will only work if the target process is currently not
>> ptraced() by another process.
>>
>
> Yup, exactly.

Dammit, I hoped we can get suspend/resume for UserModeLinux for free
with CRIU. 8-)

-- 
Thanks,
//richard

Re: [Announce] Checkpoint-restore tool v0.1

[Cyrill Gorcunov]

On Tue, Jul 31, 2012 at 10:57:58AM +0200, richard -rw- weinberger wrote:
> >
> >> crtools seem to use ptrace() to execute parasite system calls.
> >> AFAIK this will only work if the target process is currently not
> >> ptraced() by another process.
> >>
> >
> > Yup, exactly.
> 
> Dammit, I hoped we can get suspend/resume for UserModeLinux for free
> with CRIU. 8-)

We have plans to implement seizing on traced tasks but no dates at the moment ;)

	Cyrill

Re: [Announce] Checkpoint-restore tool v0.1

[Pavel Emelyanov]

On 07/31/2012 12:57 PM, richard -rw- weinberger wrote:
> On Tue, Jul 31, 2012 at 10:53 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>> On 07/30/2012 02:42 PM, richard -rw- weinberger wrote:
>>> On Mon, Jul 23, 2012 at 10:53 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>>>> This project is an attempt to implement the checkpoint-restore functionality
>>>> for processes and containers without driving too much code into the kernel tree,
>>>> but putting there "various oddball helper code" instead.
>>>
>>> Is CRIU able to checkpoint a process tree where one or more processes
>>> are traced using ptrace()?
>>
>> No it's not (currently).
>>
>>> crtools seem to use ptrace() to execute parasite system calls.
>>> AFAIK this will only work if the target process is currently not
>>> ptraced() by another process.
>>>
>>
>> Yup, exactly.
> 
> Dammit, I hoped we can get suspend/resume for UserModeLinux for free
> with CRIU. 8-)

Sorry :( However, if you can help with patches on that issue that would be
highly appreciated :)

Thanks,
Pavel

Re: [Announce] Checkpoint-restore tool v0.1

[richard -rw- weinberger]

On Tue, Jul 31, 2012 at 11:07 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
> Sorry :( However, if you can help with patches on that issue that would be
> highly appreciated :)
>

Yeah, but I fear it's not that easy.
We'd have to change crtools to work without ptrace().

-- 
Thanks,
//richard

Re: [Announce] Checkpoint-restore tool v0.1

[Pavel Emelyanov]

On 07/31/2012 01:29 PM, richard -rw- weinberger wrote:
> On Tue, Jul 31, 2012 at 11:07 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>> Sorry :( However, if you can help with patches on that issue that would be
>> highly appreciated :)
>>
> 
> Yeah, but I fear it's not that easy.
> We'd have to change crtools to work without ptrace().

Well, this is hard. Using ptrace saved us from having many special-purpose
APIs for dumping various stuff (there will be an article about it). Thus I
don't know which way is simpler -- stop using ptrace or teach ptrece to allow
several tracers to attach to one task %)

Thanks,
Pavel

Re: [Announce] Checkpoint-restore tool v0.1

[richard -rw- weinberger]

On Tue, Jul 31, 2012 at 11:54 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>> Yeah, but I fear it's not that easy.
>> We'd have to change crtools to work without ptrace().
>
> Well, this is hard. Using ptrace saved us from having many special-purpose
> APIs for dumping various stuff (there will be an article about it). Thus I
> don't know which way is simpler -- stop using ptrace or teach ptrece to allow
> several tracers to attach to one task %)

Allowing multiple tracers in a safe way is IMHO even more harder.

BTW:  While reading prctl_set_mm() I noticed two things.
1.  Why isn't the return value of find_vma() verified?
It looks like one can set an addr which does not belong to any vma.
2. What will happen if addr is not page aligned?

-- 
Thanks,
//richard

Re: [Announce] Checkpoint-restore tool v0.1

[Cyrill Gorcunov]

On Tue, Jul 31, 2012 at 12:08:22PM +0200, richard -rw- weinberger wrote:
> On Tue, Jul 31, 2012 at 11:54 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
> >> Yeah, but I fear it's not that easy.
> >> We'd have to change crtools to work without ptrace().
> >
> > Well, this is hard. Using ptrace saved us from having many special-purpose
> > APIs for dumping various stuff (there will be an article about it). Thus I
> > don't know which way is simpler -- stop using ptrace or teach ptrece to allow
> > several tracers to attach to one task %)
> 
> Allowing multiple tracers in a safe way is IMHO even more harder.
> 
> BTW:  While reading prctl_set_mm() I noticed two things.
> 1.  Why isn't the return value of find_vma() verified?

prctl_set_mm
	vma = find_vma(mm, addr);
	...
	if (!vma) {
		error = -EFAULT;
		goto out;
	}

these values are used in procfs statistics only. So I don't get
which verify you mean here.

> It looks like one can set an addr which does not belong to any vma.
> 2. What will happen if addr is not page aligned?

you'll have a bit weird output in procfs stat (probably I should add
page alignment check here).

	Cyrill

Re: [Announce] Checkpoint-restore tool v0.1

[richard -rw- weinberger]

On Tue, Jul 31, 2012 at 12:16 PM, Cyrill Gorcunov <gorcunov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org> wrote:
> On Tue, Jul 31, 2012 at 12:08:22PM +0200, richard -rw- weinberger wrote:
>> On Tue, Jul 31, 2012 at 11:54 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
>> >> Yeah, but I fear it's not that easy.
>> >> We'd have to change crtools to work without ptrace().
>> >
>> > Well, this is hard. Using ptrace saved us from having many special-purpose
>> > APIs for dumping various stuff (there will be an article about it). Thus I
>> > don't know which way is simpler -- stop using ptrace or teach ptrece to allow
>> > several tracers to attach to one task %)
>>
>> Allowing multiple tracers in a safe way is IMHO even more harder.
>>
>> BTW:  While reading prctl_set_mm() I noticed two things.
>> 1.  Why isn't the return value of find_vma() verified?
>
> prctl_set_mm
>         vma = find_vma(mm, addr);
>         ...
>         if (!vma) {
>                 error = -EFAULT;
>                 goto out;
>         }
>
> these values are used in procfs statistics only. So I don't get
> which verify you mean here.

If I do PR_SET_MM_START_BRK the if(!vma) will never be executed because
there a break in case PR_SET_MM_START_BRK.

-- 
Thanks,
//richard

Re: [Announce] Checkpoint-restore tool v0.1

[Cyrill Gorcunov]

On Tue, Jul 31, 2012 at 12:21:58PM +0200, richard -rw- weinberger wrote:
> On Tue, Jul 31, 2012 at 12:16 PM, Cyrill Gorcunov <gorcunov-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org> wrote:
> > On Tue, Jul 31, 2012 at 12:08:22PM +0200, richard -rw- weinberger wrote:
> >> On Tue, Jul 31, 2012 at 11:54 AM, Pavel Emelyanov <xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org> wrote:
> >> >> Yeah, but I fear it's not that easy.
> >> >> We'd have to change crtools to work without ptrace().
> >> >
> >> > Well, this is hard. Using ptrace saved us from having many special-purpose
> >> > APIs for dumping various stuff (there will be an article about it). Thus I
> >> > don't know which way is simpler -- stop using ptrace or teach ptrece to allow
> >> > several tracers to attach to one task %)
> >>
> >> Allowing multiple tracers in a safe way is IMHO even more harder.
> >>
> >> BTW:  While reading prctl_set_mm() I noticed two things.
> >> 1.  Why isn't the return value of find_vma() verified?
> >
> > prctl_set_mm
> >         vma = find_vma(mm, addr);
> >         ...
> >         if (!vma) {
> >                 error = -EFAULT;
> >                 goto out;
> >         }
> >
> > these values are used in procfs statistics only. So I don't get
> > which verify you mean here.
> 
> If I do PR_SET_MM_START_BRK the if(!vma) will never be executed because
> there a break in case PR_SET_MM_START_BRK.

Yes, and this is done by purpose, since we need to setup _completely_
new memory map on restore procedure.

There is a minimal check for value being sane

	if (addr >= TASK_SIZE || addr < mmap_min_addr)
		return -EINVAL;

and the address belongs to mm::start_data|end_data area. But sure,
better to add checks that at least code/data areas do exist, otherwise
the proc output will not reflect the real state of memory maps.

	Cyrill

[Announce] Checkpoint-restore tool v0.2

[Pavel Emelyanov]

Hi!

I'm happy to announce that the next big step is done by the CRIU project.

The major achievement so far -- the tool can now dump and restore a simple LXC
container. Another notable feature is the initial support for PTYs which is enough
to play with c/r of a container with active ssh sessions from outside, or with
a screen app with some simple stuff running inside.

A HOWTO describing an LXC container dump and restore is at http://criu.org/LXC


The v0.2 can be downloaded from

	http://download.openvz.org/criu/crtools-0.2.tar.bz2


Other project resources are

  documentation and news:             http://criu.org
  mainling list:                      https://openvz.org/mailman/listinfo/criu
  git repo:                           http://git.criu.org/?p=crtools.git
  kernel with not-yet-merged patches: https://github.com/cyrillos/linux-2.6.git

Thanks,
Pavel

Re: [Announce] Checkpoint-restore tool v0.2

[Serge Hallyn]

Congratulations, Pavel and criu team, that's awesome!

Quoting Pavel Emelyanov (xemul-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org):
> Hi!
> 
> I'm happy to announce that the next big step is done by the CRIU project.
> 
> The major achievement so far -- the tool can now dump and restore a simple LXC
> container. Another notable feature is the initial support for PTYs which is enough
> to play with c/r of a container with active ssh sessions from outside, or with
> a screen app with some simple stuff running inside.
> 
> A HOWTO describing an LXC container dump and restore is at http://criu.org/LXC
> 
> 
> The v0.2 can be downloaded from
> 
> 	http://download.openvz.org/criu/crtools-0.2.tar.bz2
> 
> 
> Other project resources are
> 
>   documentation and news:             http://criu.org
>   mainling list:                      https://openvz.org/mailman/listinfo/criu
>   git repo:                           http://git.criu.org/?p=crtools.git
>   kernel with not-yet-merged patches: https://github.com/cyrillos/linux-2.6.git
> 
> Thanks,
> Pavel
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