Dne 14. 10. 19 v 10:00 Gang He napsal(a):
Hello List,
By default, devices/dir configuration option in /etc/lvm/lvm.conf is "=/dev".
But, if I edit this configuration option, e.g. dir = "/dev/lvm", then lvcreate command will fail.
sles12sp4-node:/dev # lvcreate -L2G -ay -n testlv vgdata
/dev/lvm/vgdata/testlv: not found: device not cleared
Aborting. Failed to wipe start of new LV.
I am using lvm 2.02.183(or 180), this option can be edit individually?
or any other option will affect this option, then lead to lvcreate failure.
Hi
The option is not so easy to explain:
In the first place on a today's system you shall never ever need to change
this setting - as majority of systems runs 'udev' or something similar in a
fixed position /dev.
So symlinks & devices appears at this directory (and without 'lvm2' direct
work) only as a consequence of configured udev rules.
So now surely comes the obvious question - why the 'setting' even exists when
you should always use '/dev' anyway right ;) ?
And here the answer is longer - lvm2 is very 'oldish' project from 'dark' era
before udev took control over devices - and in this old era you could have
configured different device directory for devices created by lvm2 - since it's
been lvm2 physically creating these devices.
The usability for normal users is relatively questionable since almost every
user wants his devices in /dev dir anyway, but couple wanted to maintain
separate dir for lvm2 devices.
The 'other' use-case is for testing - where i.e. lvm2 test suite is/(or was)
able to run its tests in completely isolated device directory.
But to be able to use this 'capability' - one has to enable other lvm.conf
setting: 'activation/verify_udev_operations=1' - when enabled lvm2 will
ensure devices are in give directory.
But !!!! (and it's BIG BUT) this shall never be enabled on a system with
running udevd and /dev dir set - as basically nothing else then udevd is
supposed to be creating anything in /dev dir.
So hopefully this explains most of the question you may have about this setting.
Regards
Zdenek
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