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Why we need the group file while we creating the VG

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bchinnat
Frequent Advisor

Why we need the group file while we creating the VG

While we creating the VG, we are creating the group file by mknod command with minor number. And also anyone explain why we need and all the options in it like c 64 ....

Thanks In Advance...

4 REPLIES
Suraj K Sankari
Honored Contributor
Solution

Re: Why we need the group file while we creating the VG

HI,
The group special file, or control file, provides the means by which LVM kernel and LVM
commands communicate within the volume group you create.

Create the control file named group in the directory /dev/vgnn. Use the mknod(1M)
command. The group file is a character device file. The major number is always 64. The
minor number is hexadecimal, always ends in 0000, and has the following form:
0xhh0000
where hh is the hexadecimal representation of the volume group number.
For example, to create a group file for a volume group 01, you would type:

# mknod /dev/vg01/group c 64 0x010000
# chown -R root:sys /dev/vg01
# chmod 640 /dev/vg01/group

Be sure to verify the permissions on the new group file after executing the mknod command.
The group file should be owned by root, with rw-r----- permissions; otherwise,
unauthorized users may be able to access or change data stored in your logical volumes.

Suraj
Jeeshan
Honored Contributor

Re: Why we need the group file while we creating the VG

As Suraj said, yeah the mknod command represent the kernel driver association.
a warrior never quits
Sunny123_1
Esteemed Contributor

Re: Why we need the group file while we creating the VG

While creating new Volume group we have to crate the group special file with mknod command.The mknod command represent the kernel driver association.

Regards
Sunny
VK2COT
Honored Contributor

Re: Why we need the group file while we creating the VG

Hello,

And also note that mknod is not needed with
recent HP-UX 11.31 releases.

vgcreate(1M) does it automatically.
And by the way, while on the same topics,
HP-UX 11.31 has new type of
LVM VGs (L2), so this is possible too:

mknod /dev/vgXX/group c 128 ...

Admins used to memorise "c 64" but that
is not the only option any more.

And also, there is a new command for HP-UX 11.31 - vgversion(1M) which helps in
converting LVM L1 to L2.

Cheers,

VK2COT
VK2COT - Dusan Baljevic