Hi, I am using lvm2 2.01.09 on Gentoo Linux. My kernel version is 2.6.15 and I'm using udev 079. I hope the @redhat.com suffix doesn't mean this is a Red Hat-only list, but if it does I'll gladly take my question elsewhere (I have not received an answer on the Gentoo forums). I am trying to set up an LVM2 VG using a loop device. My problem is that device nodes are never created for my VG. However, my VG shows up in scans (vgscan) and displays (vgdisplay). Even vgscan --mknodes does not make the nodes. Because I never get a node for my VG, I can't figure out how I am supposed to create LV's in it. I have the modules loop, dm-mod and dm-snapshot loaded. Therefore, I do have /dev/mapper/control. Here is what I have done so far: o Create file and set up to use with loop device # dd if=/dev/zero of=/local/snapshot bs=1M count=512 # losetup /dev/loop0 /local/snapshot o Set up the PV # pvcreate /dev/loop0 o Create the VG # vgcreate snapshot /dev/loop0 At this point commands like this fail: # lvcreate -L512 -s -n backup snapshot Path required for Logical Volume "snapshot" The origin name should include the volume group. # lvcreate -L512 -s -n backup /dev/snapshot "/dev/snapshot": Invalid path for Logical Volume The origin name should include the volume group. I have read in the docs that "vgscan" is run automatically now and that I should expect to see my VG in /dev. This does not happen so I do the following: o Try to activate the VG # vgchange -a y snapshot 0 logical volume(s) in volume group "snapshot" now active o Try running vgscan manually # vgscan Reading all physical volumes. This may take a while... Found volume group "snapshot" using metadata type lvm2 # vgscan --mknodes Reading all physical volumes. This may take a while... Found volume group "snapshot" using metadata type lvm2 o No results in /dev, try vgdisplay # vgdisplay --- Volume group --- VG Name snapshot System ID Format lvm2 Metadata Areas 1 Metadata Sequence No 1 VG Access read/write VG Status resizable MAX LV 0 Cur LV 0 Open LV 0 Max PV 0 Cur PV 1 Act PV 1 VG Size 508.00 MB PE Size 4.00 MB Total PE 127 Alloc PE / Size 0 / 0 Free PE / Size 127 / 508.00 MB VG UUID RG5GM3-WrEZ-PmCM-Fl0A-wjAy-Udqo-xLASVj It looks like my VG is there, but it still isn't showing up in /dev. I read something about how if udev isn't configured properly, you will get devices like /dev/dm-# where # is 0-9, instead of named VG nodes. I don't have those either, but I follow the instructions which are to uncomment a line in my udev rules: KERNEL=="dm-[0-9]*", PROGRAM="/sbin/devmap_name %M %m", NAME="%k", SYMLINK+="%c" I learn that devmap_name is included with multipath-tools, so I install those, version 0.4.6. I reload my udev rules and repeat the steps above, but there is no change. Then I wonder if this has anything to do with the multipath target in the kernel configuration for the device mapper. I enable it, reboot for good measure, and load the multipath module. I repeat the steps above, but there is still no change. At this point I wonder if udev has some problem outside the scope of my imagination, so I try to see if I can use vgscan to create nodes outside of /dev by editing lvm.conf. When I run vgscan --mknodes, however, it still only creates mapper/control. I guess I shouldn't have really expected that to work, but it's still weird. Please CC me on replies as I am not subscribed to the list. --Geoff Mishkin <gmishkin@bu.edu>
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