Hi Zdenek, Thanks for explaining. That means we should tell the user, you should not edit this option (dir = "/dev") in the lvm.conf, right? Thanks Gang > -----Original Message----- > From: Zdenek Kabelac [mailto:zkabelac@xxxxxxxxxx] > Sent: 2019年10月14日 18:40 > To: LVM general discussion and development <linux-lvm@xxxxxxxxxx>; Gang > He <GHe@xxxxxxxx> > Subject: Re: devices/dir configuration option in /etc/lvm/lvm.conf can be > edited? > > 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 > > _______________________________________________ linux-lvm mailing list linux-lvm@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
