[dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[lixiaokeng]

When we enable multipathd.service with systemctl and reboot,
multipathd doesn't start and log "failed to create pidfile".

The reason is following:

The RUN is /var/run in multipath-tools. When we start linux, we
mount a disk to /var. So if multipathd.service start before mount,
it will fail to activate.(If mount firstly, multipathd will start
successfully)

The RUN is defined in Makefile.inc:

ifndef RUN
        ifeq ($(shell test -L /var/run -o ! -d /var/run && echo 1),1)
                RUN=run
        else
                RUN=var/run
        endif
endif

Can it always be defined as run?

Regards,
Lixiaokeng

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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[Benjamin Marzinski]

On Thu, Jul 22, 2021 at 10:51:22AM +0800, lixiaokeng wrote:
> When we enable multipathd.service with systemctl and reboot,
> multipathd doesn't start and log "failed to create pidfile".
> 
> The reason is following:
> 
> The RUN is /var/run in multipath-tools. When we start linux, we
> mount a disk to /var. So if multipathd.service start before mount,
> it will fail to activate.(If mount firstly, multipathd will start
> successfully)
> 
> The RUN is defined in Makefile.inc:
> 
> ifndef RUN
>         ifeq ($(shell test -L /var/run -o ! -d /var/run && echo 1),1)
>                 RUN=run
>         else
>                 RUN=var/run
>         endif
> endif
> 
> Can it always be defined as run?

I believe all modern distributions make /var/run a symlink to /run.
However, if that's the case, then I don't understand why you are running
into this issue at all, since multipath should be using /run. What
multipath packages are you using?

-Ben

> 
> Regards,
> Lixiaokeng

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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[lixiaokeng]

On 2021/7/23 5:42, Benjamin Marzinski wrote:
> On Thu, Jul 22, 2021 at 10:51:22AM +0800, lixiaokeng wrote:
>> When we enable multipathd.service with systemctl and reboot,
>> multipathd doesn't start and log "failed to create pidfile".
>>
>> The reason is following:
>>
>> The RUN is /var/run in multipath-tools. When we start linux, we
>> mount a disk to /var. So if multipathd.service start before mount,
>> it will fail to activate.(If mount firstly, multipathd will start
>> successfully)
>>
>> The RUN is defined in Makefile.inc:
>>
>> ifndef RUN
>>         ifeq ($(shell test -L /var/run -o ! -d /var/run && echo 1),1)
>>                 RUN=run
>>         else
>>                 RUN=var/run
>>         endif
>> endif
>>
>> Can it always be defined as run?
> 
> I believe all modern distributions make /var/run a symlink to /run.
> However, if that's the case, then I don't understand why you are running
> into this issue at all, since multipath should be using /run. What
> multipath packages are you using?
Yes, there is a symlink to /run in /var. But it is in the disk (such as
sdb) mounted on /var actually. When reboot, systemd start multipathd
service firstly then mount sdb to /var. In this way, the multipath
service will not start.

After sdb mounted to /var, we can start multipathd service successfully.

> 
> -Ben
> 
>>
>> Regards,
>> Lixiaokeng
> 
> .
> 

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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[Benjamin Marzinski]

On Fri, Jul 23, 2021 at 02:27:58PM +0800, lixiaokeng wrote:
> 
> 
> On 2021/7/23 5:42, Benjamin Marzinski wrote:
> > On Thu, Jul 22, 2021 at 10:51:22AM +0800, lixiaokeng wrote:
> >> When we enable multipathd.service with systemctl and reboot,
> >> multipathd doesn't start and log "failed to create pidfile".
> >>
> >> The reason is following:
> >>
> >> The RUN is /var/run in multipath-tools. When we start linux, we
> >> mount a disk to /var. So if multipathd.service start before mount,
> >> it will fail to activate.(If mount firstly, multipathd will start
> >> successfully)
> >>
> >> The RUN is defined in Makefile.inc:
> >>
> >> ifndef RUN
> >>         ifeq ($(shell test -L /var/run -o ! -d /var/run && echo 1),1)
> >>                 RUN=run
> >>         else
> >>                 RUN=var/run
> >>         endif
> >> endif
> >>
> >> Can it always be defined as run?
> > 
> > I believe all modern distributions make /var/run a symlink to /run.
> > However, if that's the case, then I don't understand why you are running
> > into this issue at all, since multipath should be using /run. What
> > multipath packages are you using?
> Yes, there is a symlink to /run in /var. But it is in the disk (such as
> sdb) mounted on /var actually. When reboot, systemd start multipathd
> service firstly then mount sdb to /var. In this way, the multipath
> service will not start.
> 
> After sdb mounted to /var, we can start multipathd service successfully.

But when the binaries were compiled, if /var/run existed and was a
symlink in your build environment, then RUN should equal "run", and
multipath should should be using /run instead of /var/run, right?

This is why I asked what multipath packages are you using.

-Ben
 
> > 
> > -Ben
> > 
> >>
> >> Regards,
> >> Lixiaokeng
> > 
> > .
> > 

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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[lixiaokeng]

>> After sdb mounted to /var, we can start multipathd service successfully.
> 
> But when the binaries were compiled, if /var/run existed and was a
> symlink in your build environment, then RUN should equal "run", and
> multipath should should be using /run instead of /var/run, right?
> 
> This is why I asked what multipath packages are you using.
> 
This problem is found in 0.7.7.

Regards,
Lixiaokeng

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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[Benjamin Marzinski]

On Mon, Jul 26, 2021 at 08:22:49PM +0800, lixiaokeng wrote:
> 
> >> After sdb mounted to /var, we can start multipathd service successfully.
> > 
> > But when the binaries were compiled, if /var/run existed and was a
> > symlink in your build environment, then RUN should equal "run", and
> > multipath should should be using /run instead of /var/run, right?
> > 
> > This is why I asked what multipath packages are you using.
> > 
> This problem is found in 0.7.7.

Sorry. I wasn't very clear with what I was asking for.  Unless I'm
missing something here, if multipathd is trying to use /var/run, that
means that when the multipathd binary was compiled, it was compiled on a
machine where /var/run was not a symlink. 

So, I'm wondering where your multipathd binary got compiled. Are you
using a packaged version from a distribution like RHEL, SLES, Fedora,
Ubuntu, etc? Did you compile it yourself?

When I run multipathd under strace, I can see:

openat(AT_FDCWD, "/run/multipathd.pid", O_WRONLY|O_CREAT, 0644) = 3

The multipathd binary I'm using was compiled on a machine where /var/run
is a symlink to /run, so multipathd directly uses /run, instead of using
/var/run. I'm assuming that whatever machine your multipathd binary was
compiled on, /var/run was a directory. Do you know if that's possible?

-Ben

> 
> Regards, Lixiaokeng

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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[Martin Wilck]

On Mo, 2021-07-26 at 11:28 -0500, Benjamin Marzinski wrote:
> On Mon, Jul 26, 2021 at 08:22:49PM +0800, lixiaokeng wrote:
> > 
> > > > After sdb mounted to /var, we can start multipathd service
> > > > successfully.
> > > 
> > > But when the binaries were compiled, if /var/run existed and was
> > > a
> > > symlink in your build environment, then RUN should equal "run",
> > > and
> > > multipath should should be using /run instead of /var/run, right?
> > > 
> > > This is why I asked what multipath packages are you using.
> > > 
> > This problem is found in 0.7.7.
> 
> Sorry. I wasn't very clear with what I was asking for.  Unless I'm
> missing something here, if multipathd is trying to use /var/run, that
> means that when the multipathd binary was compiled, it was compiled
> on a
> machine where /var/run was not a symlink. 
> 
> So, I'm wondering where your multipathd binary got compiled. Are you
> using a packaged version from a distribution like RHEL, SLES, Fedora,
> Ubuntu, etc? Did you compile it yourself?
> 
> When I run multipathd under strace, I can see:
> 
> openat(AT_FDCWD, "/run/multipathd.pid", O_WRONLY|O_CREAT, 0644) = 3
> 
> The multipathd binary I'm using was compiled on a machine where
> /var/run
> is a symlink to /run, so multipathd directly uses /run, instead of
> using
> /var/run. I'm assuming that whatever machine your multipathd binary
> was
> compiled on, /var/run was a directory. Do you know if that's
> possible?

Ack. Lixiaokeng, can you answer Ben's question?

Regards,
Martin



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Re: [dm-devel] [Question] multipathd.service start failed when /var/run isn't mount

[lixiaokeng]

On 2021/8/12 19:09, Martin Wilck wrote:
> On Mo, 2021-07-26 at 11:28 -0500, Benjamin Marzinski wrote:
>> On Mon, Jul 26, 2021 at 08:22:49PM +0800, lixiaokeng wrote:
>>>
>>>>> After sdb mounted to /var, we can start multipathd service
>>>>> successfully.
>>>>
>>>> But when the binaries were compiled, if /var/run existed and was
>>>> a
>>>> symlink in your build environment, then RUN should equal "run",
>>>> and
>>>> multipath should should be using /run instead of /var/run, right?
>>>>
>>>> This is why I asked what multipath packages are you using.
>>>>
>>> This problem is found in 0.7.7.
>>
>> Sorry. I wasn't very clear with what I was asking for.  Unless I'm
>> missing something here, if multipathd is trying to use /var/run, that
>> means that when the multipathd binary was compiled, it was compiled
>> on a
>> machine where /var/run was not a symlink. 
>>
>> So, I'm wondering where your multipathd binary got compiled. Are you
>> using a packaged version from a distribution like RHEL, SLES, Fedora,
>> Ubuntu, etc? Did you compile it yourself?
>>
>> When I run multipathd under strace, I can see:
>>
>> openat(AT_FDCWD, "/run/multipathd.pid", O_WRONLY|O_CREAT, 0644) = 3
>>
>> The multipathd binary I'm using was compiled on a machine where
>> /var/run
>> is a symlink to /run, so multipathd directly uses /run, instead of
>> using
>> /var/run. I'm assuming that whatever machine your multipathd binary
>> was
>> compiled on, /var/run was a directory. Do you know if that's
>> possible?
> 
> Ack. Lixiaokeng, can you answer Ben's question?
> 
> Regards,
> Martin
> 

Hi Martin, Ben:
I'm sorry for missing reply. The situation is the same as ben said.
The /var/run in compile machine is a directory, but it is a symlink
in using machine.

Thanks Ben's help again.

Regards,
Lixiaokeng


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