Bug#606124: Workaround

[Alex King]

The upstream template seems to be flawed in two ways.

The file name (12-dm-permissions.rules) puts it in the udev rules too 
early to use environment variables (e.g.. ENV{DM_VG_NAME}).

Apparently in RHEL6 these values are set up in files named at 10 and 11 
priority, but in debian they are set up in 
/lib/udev/rules.d/56-lvm.rules and or 
/lib/udev/rules.d/60-persistent-storage-lvm.rules, so to be safe I used 
62-dm-permissions.rules.

Secondly the template file has the following lines:

# "add" event is processed on coldplug only!
ACTION!="add|change", GOTO="dm_end"
ENV{DM_UDEV_RULES_VSN}!="?*", GOTO="dm_end"


at the start, and

LABEL="dm_end"

at the end.

There is already a good template installed at 
/usr/share/doc/dmsetup/examples/udev-dm-permissions.rules including LVM 
examples, but there is no guidance on how to use it.  I found this file 
after having done a lot of work

When I copied it to /etc/udev/rules.d and filled it in with appropriate 
values, it worked for me.

The other problem I initially thought I was encountering was when lvm is 
bought up in the initramfs, (e.g. root file system on lvm,) any user 
entered rules file in /etc/udev/rules.d/ is not copied into the initrd.  
However, for file systems not needed at initramfs time, this does not 
matter, it seems lvm sets them up correctly later in boot.

I suggest a note in /usr/share/doc/lvm2/README.Debian

"To change the permissions or ownership of a LVM device and have it 
persist across reboot, for example for a daemon that works directly with 
disk partitions, you need an appropriate udev rule.  Copy 
/usr/share/doc/dmsetup/examples/udev-dm-permissions.rules to /etc/udev.d 
and modify it to mention the required ownership and permissions."

Cheers,
Alex