From mboxrd@z Thu Jan 1 00:00:00 1970 References: From: Zdenek Kabelac Message-ID: <5b456c7b-13bf-b7fc-9347-eb54ccb6cc72@redhat.com> Date: Mon, 14 Oct 2019 12:39:45 +0200 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US Content-Transfer-Encoding: 7bit Subject: Re: [linux-lvm] devices/dir configuration option in /etc/lvm/lvm.conf can be edited? Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: LVM general discussion and development , Gang He 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