Centos 7.2 Convert single LVM to RAID Mirror Reinstall BootLoader Post: 302971389

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Operating Systems Linux Centos 7.2 Convert single LVM to RAID Mirror Reinstall BootLoader Post 302971389 by Clovis_Sangrail on Tuesday 19th of April 2016 03:58:39 PM

04-19-2016

Registered User

Centos 7.2 Convert single LVM to RAID Mirror Reinstall BootLoader

Hello,
I am trying to convert a single-drive Centos 7.2 installation with LVM into a two-disk mdadm mirror with mrrored LVM. I was able to follow the excellent instructions at:

HTML Code:

http://www.dgoradia.com/creating-a-raid1-mirrored-on-an-existing-centos-on-lvm/

and did create a two-disk mirror of both the original boot partition and the LVM partition. When I boot off a live Centos 7.2 DVD with the mirrored drives installed it does find the mirrors, and I can fsck and mount the boot and LVM filesystems in it.

Code:

[root@new-host-4 ~]# lsblk
NAME              MAJ:MIN RM   SIZE RO TYPE  MOUNTPOINT
sda                 8:0    0 465.8G  0 disk  
├─sda1              8:1    0     1G  0 part  
│ └─md126           9:126  0  1024M  0 raid1 
└─sda2              8:2    0   115G  0 part  
  └─md127           9:127  0   115G  0 raid1 
    ├─centos-root 253:3    0    40G  0 lvm   
    ├─centos-swap 253:4    0     9G  0 lvm   
    ├─centos-home 253:5    0    25G  0 lvm   
    └─centos-var  253:6    0    40G  0 lvm   
sdb                 8:16   0 465.8G  0 disk  
├─sdb1              8:17   0     1G  0 part  
│ └─md126           9:126  0  1024M  0 raid1 
└─sdb2              8:18   0   115G  0 part  
  └─md127           9:127  0   115G  0 raid1 
    ├─centos-root 253:3    0    40G  0 lvm   
    ├─centos-swap 253:4    0     9G  0 lvm   
    ├─centos-home 253:5    0    25G  0 lvm   
    └─centos-var  253:6    0    40G  0 lvm   
sr0                11:0    1   4.4G  0 rom   /run/initramfs/live
loop0               7:0    0    20K  1 loop  
loop1               7:1    0   4.3M  1 loop  
└─live-osimg-min  253:2    0     8G  1 dm    
loop2               7:2    0     1G  1 loop  
loop3               7:3    0     8G  1 loop  
├─live-rw         253:0    0     8G  0 dm    /
├─live-base       253:1    0     8G  1 dm    
└─live-osimg-min  253:2    0     8G  1 dm    
loop4               7:4    0   512M  0 loop  
└─live-rw         253:0    0     8G  0 dm    /
[root@new-host-4 ~]#

However these instructions are specific to Centos 6, and the section for installing a bootloader on the new mirror completely does not apply in Centos 7. In Centos 7.2 there does not seem to be any commandline utility that provides a "grub>" command prompt, ant the grub binary itself is replaced by a bunch of "grub2-*" executables.

Can anyone explain how to reinstall the bootloader on the new mirror? The Centos 6 instructions say it must be installed separately on sda1 and sdb1.

Last edited by Clovis_Sangrail; 04-19-2016 at 07:34 PM..

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LEARN ABOUT XFREE86

pvck

PVCK(8) 						      System Manager's Manual							   PVCK(8)

NAME

       pvck - check physical volume metadata

SYNOPSIS

       pvck [-d|--debug] [-h|--help] [-v|--verbose] [--labelsector] PhysicalVolume [PhysicalVolume...]

DESCRIPTION

       pvck checks physical volume LVM metadata for consistency.

OPTIONS

       See lvm for common options.

       --labelsector sector
	      By  default, 4 sectors of PhysicalVolume are scanned for an LVM label, starting at sector 0.  This parameter allows you to specify a
	      different starting sector for the scan and is useful for recovery situations.  For example, suppose the partition table is corrupted
	      or  lost	on  /dev/sda, but you suspect there was an LVM partition at approximately 100 MB.  This area of the disk may be scanned by
	      using the --labelsector parameter with a value of 204800 (100 * 1024 * 1024 / 512 = 204800):

	      pvck --labelsector 204800 /dev/sda

	      Note that a script can be used with --labelsector to automate the process of finding LVM labels.

SEE ALSO

       lvm(8), pvcreate(8), pvscan(8) vgck(8)

Sistina Software UK					 LVM TOOLS 2.02.95(2) (2012-03-06)						   PVCK(8)

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