[linux-lvm] problem with lvcreate and redirection

Lentes, Bernd bernd.lentes at helmholtz-muenchen.de
Sat Feb 20 13:25:51 UTC 2016

----- Am 19. Feb 2016 um 21:31 schrieb Zdenek Kabelac zdenek.kabelac at gmail.com:

> Dne 19.2.2016 v 19:40 Lentes, Bernd napsal(a):
>> Hi,
>> i have a script in which i invoke lvremove and lvcreate. With lvremove i don't
>> have proplems but with lvcreate.
>> I'm redirecting stdout and stderr to a file because the script is executed by
>> cron and i'd like to have a look afterwards if everything went fine.
>> The command is: lvcreate -v -L 25G -n lv_root_snapshot -s vg1/lv_root >
>> lvcreate_with_redirection.log 2>&1. Shell does not accept further commands
>> afterwards, but host still responds to ping. You can have a look on
>> lvcreate_with_redirection.log here:
>> https://hmgubox.helmholtz-muenchen.de:8001/d/b4c7025bac/ .
>> System seems to stop while suspending.
>> last lines of the log:
>> ======================================================
>> ...
>>      Creating vg1-lv_root_snapshot-cow
>>      Loading vg1-lv_root_snapshot-cow table (252:3)
>>      Resuming vg1-lv_root_snapshot-cow (252:3)
>>      Loading vg1-lv_root_snapshot table (252:1)
>>      Suspending vg1-lv_root (252:0) with filesystem sync with device flush
>> ======================================================
> Unfortunately you can't do that if you log to the SAME volume you are
> suspending - i.e. you run your command from your root volume
> which is also suspended.
> We could likely 'buffer' the output while in suspend mode,
> and throw out the output later - but as this is seen as 'debug' help it's
> assume user takes care and user place for logging which doesn't block.
> So if you want to see logs - use something tmpfs location for it.
> Regards
> Zdenek

Hi Zdenek,

thanks for your answer. I redirected the output already to another partition, but system still stopped. Maybe because the partition is on the same disk as the lv ? Whole disk is suspended ? It's not possible to suspend just a partition ? I will try with tmpfs or something else.
But does that mean that redirection is generally not possible when suspending a lv ? Or just in my case because i invoke lvcreate ? What is about other programs having redirections during the suspend ? And why does it work when i just rediredt stdout ? When i redirect stdout and stderr system stops.

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