View source for HowTo Change The LVM Volume Group Name That Includes The Root Partition

__TOC__
= Overview =
This page describes the steps needed to change an '''[http://en.wikipedia.org/wiki/Logical_Volume_Manager_(Linux) LVM (Logical Volume Manager)]''' '''Volume Group''' name which includes the the Root partition ("'''/'''"). The problem is that the Root partition '''[http://en.wikipedia.org/wiki/Device_mapper LVM Device Mapper]''' is referenced in different configuration files and embedded in the '''[http://en.wikipedia.org/wiki/Initramfs Kernel initramfs]'''.

We will demonstrate the LVM Volume Group name change from "'''nst_localhost'''" to "'''nst20'''".

= State Before The LVM Volume Group Name Change =
The '''[http://fedoraproject.org/wiki/Features/SystemStorageManager Fedora System Storage Manager]''' utility: '''ssm''' is used to display the current storage layout on the example system.

 [root@localhost ~]# ssm list
 -------------------------------------------------------------------
 Device        Free      Used      Total  Pool           Mount point  
 -------------------------------------------------------------------
 /dev/sda                       30.00 GB                 PARTITIONED  
 /dev/sda1                     500.00 MB                 /boot        
 /dev/sda2  0.00 KB  29.51 GB   29.51 GB  nst_localhost               
 -------------------------------------------------------------------
 ---------------------------------------------------------
 Pool           Type  Devices     Free      Used     Total  
 ---------------------------------------------------------
 nst_localhost  lvm   1        0.00 KB  29.51 GB  29.51 GB  
 ---------------------------------------------------------
 ----------------------------------------------------------------------------------------------------
 Volume                   Pool           Volume size  FS      FS size       Free  Type    Mount point  
 ----------------------------------------------------------------------------------------------------
 /dev/nst_localhost/root  nst_localhost     27.48 GB  ext4   27.48 GB   19.18 GB  linear  /            
 /dev/nst_localhost/swap  nst_localhost      2.03 GB                              linear               
 /dev/sda1                                 500.00 MB  ext4  500.00 MB  364.40 MB  part    /boot        
 ----------------------------------------------------------------------------------------------------

= Steps To Change The LVM Volume Group Name =
== Step 1: Change Volume Group Name ==
The '''[http://man.cx/vgrename(8) vgrename]''' utility will be used to change LVM Volume Name from "'''nst_localhost'''" to "'''nst20'''":
 [root@localhost ~]# vgrename -v nst_localhost nst20
     Checking for existing volume group "nst_localhost"
     Checking for new volume group "nst20"
     Archiving volume group "nst_localhost" metadata (seqno 5).
     Writing out updated volume group
     Renaming "/dev/nst_localhost" to "/dev/nst20"
     Loading nst_localhost-root table (253:0)
     Suppressed nst_localhost-root (253:0) identical table reload.
     Suspending nst_localhost-root (253:0) with device flush
     Loading nst_localhost-root table (253:0)
     Suppressed nst_localhost-root (253:0) identical table reload.
     Renaming nst_localhost-root (253:0) to nst20-root
     Resuming nst20-root (253:0)
     Loading nst_localhost-swap table (253:1)
     Suppressed nst_localhost-swap (253:1) identical table reload.
     Suspending nst_localhost-swap (253:1) with device flush
     Loading nst_localhost-swap table (253:1)
     Suppressed nst_localhost-swap (253:1) identical table reload.
     Renaming nst_localhost-swap (253:1) to nst20-swap
     Resuming nst20-swap (253:1)
     Creating volume group backup "/etc/lvm/backup/nst20" (seqno 6).
   Volume group "nst_localhost" successfully renamed to "nst20"
     Wiping cache of LVM-capable devices
     Wiping internal VG cache

== Step 2: Update The File System Configuration File: "/etc/fstab" ==
Use an editor (e.g., '''vi''') to change the LVM Volume Group Device Mapper name in the file system configuration file: "'''/etc/fstab'''" to the new "'''nst20'''" name  for the "'''root'''" and "'''swap'''" Logical Volumes.

'''Before:'''
 [root@localhost ~]# cat /etc/fstab
 
 #
 # /etc/fstab
 # Created by anaconda on Mon Dec 30 05:16:54 2013
 #
 # Accessible filesystems, by reference, are maintained under '/dev/disk'
 # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
 #
 /dev/mapper/'''nst_localhost'''-root /                       ext4    defaults        1 1
 UUID=8c72887d-d7db-4a3d-9b09-0d619fc11d9c /boot                   ext4    defaults        1 2
 /dev/mapper/'''nst_localhost'''-swap swap                    swap    defaults        0 0

'''After:'''
 [root@localhost ~]# cat /etc/fstab
 
 #
 # /etc/fstab
 # Created by anaconda on Mon Dec 30 05:16:54 2013
 #
 # Accessible filesystems, by reference, are maintained under '/dev/disk'
 # See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
 #
 /dev/mapper/'''nst20'''-root /                       ext4    defaults        1 1
 UUID=8c72887d-d7db-4a3d-9b09-0d619fc11d9c /boot                   ext4    defaults        1 2
 /dev/mapper/'''nst20'''-swap swap                    swap    defaults        0 0

== Step 3: Update The Grub2 Configuration File: "/boot/grub2/grub.cfg" ==
Use an editor (e.g., '''vi''') to change the LVM Volume Group Device Mapper name in the file system configuration file: "'''/boot/grub2/grub.cfg'''" to the new "'''nst20'''" name  for the "'''root'''" and "'''swap'''" Logical Volumes for all relevant entries.

'''Before''' ('''Note''': Only one Grub2 menu entry is shown for example purposes. All relevant entries need to be changed.):
 .
 .
 .
 menuentry " ---------------------NST 20 (64 Bit) Boot Choices---------------------" {
   true
 }
 
 menuentry 'Console, Kernel: 3.12.5-302.fc20.x86_64' --class nst --class gnu-linux --class gnu --class os {
         savedefault
     load_video
         set gfxpayload=keep
         insmod gzio
         insmod part_msdos
         insmod ext2
         set root='hd0,msdos1'
         if [ x$feature_platform_search_hint = xy ]; then
           search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  8c72887d-d7db-4a3d-9b09-0d619fc11d9c
         else
           search --no-floppy --fs-uuid --set=root 8c72887d-d7db-4a3d-9b09-0d619fc11d9c
         fi
         echo    'Loading Linux 3.12.5-302.fc20.x86_64 ...'
         linux   /vmlinuz-3.12.5-302.fc20.x86_64 root=/dev/mapper/'''nst_localhost'''-root ro rd.lvm.lv='''nst_localhost'''/swap rd.lvm.lv='''nst_localhost'''/root vconsole.font=latarcyrheb-sun16 crashkernel=auto systemd.unit=multi-user.target
         echo    'Loading initial ramdisk ...'
         initrd  /initramfs-3.12.5-302.fc20.x86_64.img
 }
 .
 .
 .

'''After:'''
 .
 .
 .
 menuentry " ---------------------NST 20 (64 Bit) Boot Choices---------------------" {
   true
 }
 
 menuentry 'Console, Kernel: 3.12.5-302.fc20.x86_64' --class nst --class gnu-linux --class gnu --class os {
         savedefault
     load_video
         set gfxpayload=keep
         insmod gzio
         insmod part_msdos
         insmod ext2
         set root='hd0,msdos1'
         if [ x$feature_platform_search_hint = xy ]; then
           search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  8c72887d-d7db-4a3d-9b09-0d619fc11d9c
         else
           search --no-floppy --fs-uuid --set=root 8c72887d-d7db-4a3d-9b09-0d619fc11d9c
         fi
         echo    'Loading Linux 3.12.5-302.fc20.x86_64 ...'
         linux   /vmlinuz-3.12.5-302.fc20.x86_64 root=/dev/mapper/'''nst20'''-root ro rd.lvm.lv='''nst20'''/swap rd.lvm.lv='''nst20'''/root vconsole.font=latarcyrheb-sun16 crashkernel=auto systemd.unit=multi-user.target
         echo    'Loading initial ramdisk ...'
         initrd  /initramfs-3.12.5-302.fc20.x86_64.img
 }
 .
 .
 .

== Step 4: Rebuild The Kernel initramfs File ==
The Kernel '''[http://en.wikipedia.org/wiki/Initramfs initramfs]''' image needs to be rebuild to reflect the LVM Volume Group name change. The '''[http://man7.org/linux/man-pages/man8/mkinitrd.8.html mkinitrd]''' will be used to accomplish this task which uses the "'''[https://dracut.wiki.kernel.org/index.php/Main_Page dracut]'''" tool.

'''Example for Kernel:  3.12.5-302.fc20.x86_64'''
 [root@localhost ~]# ls -al /boot/initramfs-3.12.5-302.fc20.x86_64.img
 -rw------- 1 root root 11435288 Jan  1 11:07 /boot/initramfs-3.12.5-302.fc20.x86_64.img

 [root@localhost ~]# uname -r
 3.12.5-302.fc20.x86_64 

 [root@localhost ~]# mkinitrd -f -v /boot/initramfs-$(uname -r).img $(uname -r)
 Creating: target|kernel|dracut args|basicmodules 
 Executing: /usr/sbin/dracut -v -f /boot/initramfs-3.12.5-302.fc20.x86_64.img 3.12.5-302.fc20.x86_64
 *** Including module: bash ***
 *** Including module: i18n ***
 *** Including module: ifcfg ***
 *** Including module: drm ***
 *** Including module: plymouth ***
 *** Including module: dm ***
 Skipping udev rule: 64-device-mapper.rules
 Skipping udev rule: 60-persistent-storage-dm.rules
 Skipping udev rule: 55-dm.rules
 *** Including module: kernel-modules ***
 *** Including module: lvm ***
 Skipping udev rule: 64-device-mapper.rules
 Skipping udev rule: 56-lvm.rules
 Skipping udev rule: 60-persistent-storage-lvm.rules
 *** Including module: resume ***
 *** Including module: rootfs-block ***
 *** Including module: terminfo ***
 *** Including module: udev-rules ***
 Skipping udev rule: 91-permissions.rules
 *** Including module: biosdevname ***
 *** Including module: systemd ***
 *** Including module: usrmount ***
 *** Including module: base ***
 *** Including module: fs-lib ***
 *** Including module: shutdown ***
 *** Including modules done ***
 *** Installing kernel module dependencies and firmware ***
 *** Installing kernel module dependencies and firmware done ***
 *** Resolving executable dependencies ***
 *** Resolving executable dependencies done***
 *** Pre-linking files ***
 *** Pre-linking files done ***
 *** Hardlinking files ***
 *** Hardlinking files done ***
 *** Stripping files ***
 *** Stripping files done ***
 *** Creating image file ***
 *** Creating image file done ***

 [root@localhost ~]# ls -al /boot/initramfs-3.12.5-302.fc20.x86_64.img
 -rw------- 1 root root 11435512 Jan  1 14:20 /boot/initramfs-3.12.5-302.fc20.x86_64.img

== Step 5: Reboot The System ==
After all the above changes have been made, use the '''[https://wiki.archlinux.org/index.php/systemd systemctl]''' utility to reboot your system:

 [root@localhost ~]# systemctl reboot

= State After The LVM Volume Group Name Change =
The '''[http://fedoraproject.org/wiki/Features/SystemStorageManager Fedora System Storage Manager]''' utility: '''ssm''' is used to display the storage layout on the example system after changing the LVM Volume Group Name and a system reboot has occurred.

 [root@localhost ~]# ssm list
 -----------------------------------------------------------
 Device        Free      Used      Total  Pool   Mount point  
 -----------------------------------------------------------
 /dev/sda                       30.00 GB         PARTITIONED  
 /dev/sda1                     500.00 MB         /boot        
 /dev/sda2  0.00 KB  29.51 GB   29.51 GB  nst20               
 -----------------------------------------------------------
 -------------------------------------------------
 Pool   Type  Devices     Free      Used     Total  
 -------------------------------------------------
 nst20  lvm   1        0.00 KB  29.51 GB  29.51 GB  
 -------------------------------------------------
 ------------------------------------------------------------------------------------
 Volume           Pool   Volume size  FS      FS size       Free  Type    Mount point  
 ------------------------------------------------------------------------------------
 /dev/nst20/root  nst20     27.48 GB  ext4   27.48 GB   19.18 GB  linear  /            
 /dev/nst20/swap  nst20      2.03 GB                              linear               
 /dev/sda1                 500.00 MB  ext4  500.00 MB  364.40 MB  part    /boot        
 ------------------------------------------------------------------------------------