OS Migration Across Local Disks - Oracle Linux 8

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Host has 1 disk with 2 partitions (/boot and / of type xfs).

Adding another disk of same size.

[root@oraclevm ~]# fdisk -l  | grep -i disk  | grep -i dev

Disk /dev/nvme0n1: 20 GiB, 21474836480 bytes, 41943040 sectors

Disk /dev/nvme0n2: 20 GiB, 21474836480 bytes, 41943040 sectors

Disk /dev/mapper/ol-root: 17 GiB, 18249416704 bytes, 35643392 sectors

Disk /dev/mapper/ol-swap: 2 GiB, 2147483648 bytes, 4194304 sectors

[root@oraclevm ~]#

Existing OS:

[root@oraclevm ~]# df -TH | grep -i xfs

/dev/mapper/ol-root xfs        19G  5.6G   13G  31% /

/dev/nvme0n1p1      xfs       1.1G  311M  754M  30% /boot

[root@oraclevm ~]#

Format the new disk in the same layout as 1st disk: /dev/nvme0n1:

[root@oraclevm ~]# fdisk -l /dev/nvme0n1
Disk /dev/nvme0n1: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x1c2f4a7c

Device         Boot   Start      End  Sectors Size Id Type
/dev/nvme0n1p1 *       2048  2099199  2097152   1G 83 Linux
/dev/nvme0n1p2      2099200 41943039 39843840  19G 8e Linux LVM
[root@oraclevm ~]#

[root@oraclevm ~]# fdisk /dev/nvme0n2

Welcome to fdisk (util-linux 2.32.1).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.


Command (m for help): p
Disk /dev/nvme0n2: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x25d7b68c

Device         Boot   Start      End  Sectors Size Id Type
/dev/nvme0n2p1         2048  2099199  2097152   1G 83 Linux
/dev/nvme0n2p2      2099200 41943039 39843840  19G 83 Linux

Command (m for help):

Edit the "boot" flag on /dev/nvme0n2p1:

Command (m for help): a
Partition number (1,2, default 2): 1

The bootable flag on partition 1 is enabled now.

Command (m for help): p
Disk /dev/nvme0n2: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x25d7b68c

Device         Boot   Start      End  Sectors Size Id Type
/dev/nvme0n2p1 *       2048  2099199  2097152   1G 83 Linux
/dev/nvme0n2p2      2099200 41943039 39843840  19G 83 Linux

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

[root@oraclevm ~]#

Lets migrate /boot first to the new disk and boot it.

Existing OS is created based on LVM but I am going to copy it as standard partiton.

/boot migration:

Format the partition as "xfs".

[root@oraclevm ~]# mkfs.xfs /dev/nvme0n2p1

[root@oraclevm ~]# mount /dev/nvme0n2p1 /tmp_boot
[root@oraclevm ~]# df -TH /tmp_boot
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/nvme0n2p1 xfs   1.1G   42M  1.1G   4% /tmp_boot
[root@oraclevm ~]#

I am using xfsdump and xfsrestore for data copy.

[root@oraclevm ~]# xfsdump -f /tmp/boot.img /boot

[root@oraclevm ~]# xfsrestore -f /tmp/boot.img /tmp_boot/

Repeat the same for root (/):

[root@oraclevm default]# mkfs.xfs /dev/nvme0n2p2

[root@oraclevm /]# mkdir /tmp_os
[root@oraclevm /]# mount /dev/nvme0n2p2 /tmp_os

[root@oraclevm /]# df -TH /tmp_os
Filesystem     Type  Size  Used Avail Use% Mounted on
/dev/nvme0n2p2 xfs    21G   12G  9.1G  56% /tmp_os
[root@oraclevm /]#

[root@oraclevm /]#  blkid  | grep -i "/dev/nvme0n2"
/dev/nvme0n2p1: UUID="bb83e8cd-16ad-4aff-a3f4-4a9505d9b5ca" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="25d7b68c-01"
/dev/nvme0n2p2: UUID="35e305ec-c8d4-40f9-a9e8-98dc3b27f565" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="25d7b68c-02"
/dev/nvme0n2: PTUUID="25d7b68c" PTTYPE="dos"
[root@oraclevm /]#

Lets update GRUB_CMDLINE_LINUX and GRUB_ENABLE_BLSCFG=false in /etc/default/grub. This will prevent GRUB from recreating new GRUB configuration during boot.

Old entry: GRUB_CMDLINE_LINUX="resume=/dev/mapper/ol-swap rd.lvm.lv=ol/root rd.lvm.lv=ol/swap rhgb quiet"

[root@oraclevm /]#  blkid  | grep -i "/dev/nvme0n2"
/dev/nvme0n2p1: UUID="bb83e8cd-16ad-4aff-a3f4-4a9505d9b5ca" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="25d7b68c-01"
/dev/nvme0n2p2: UUID="35e305ec-c8d4-40f9-a9e8-98dc3b27f565" BLOCK_SIZE="512" TYPE="xfs" PARTUUID="25d7b68c-02"
/dev/nvme0n2: PTUUID="25d7b68c" PTTYPE="dos"
[root@oraclevm /]#

[root@oraclevm /]# cat /etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=false
[root@oraclevm /]#

Once updated, Re-Create GRUB.

[root@oraclevm /]# grub2-mkconfig -o /boot/grub2/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.4.17-2136.307.3.1.el8uek.x86_64
Found initrd image: /boot/initramfs-5.4.17-2136.307.3.1.el8uek.x86_64.img
Found linux image: /boot/vmlinuz-4.18.0-372.9.1.el8.x86_64
Found initrd image: /boot/initramfs-4.18.0-372.9.1.el8.x86_64.img
Found linux image: /boot/vmlinuz-0-rescue-e9ce9a3dac2048a8bab69e64e6f64d92
Found initrd image: /boot/initramfs-0-rescue-e9ce9a3dac2048a8bab69e64e6f64d92.img
Found Oracle Linux Server 8.6 on /dev/nvme0n2p2
done
[root@oraclevm /]#

Install GRUB on /dev/nvme0n2.

[root@oraclevm /]# grub2-install /dev/nvme0n2
Installing for i386-pc platform.
Installation finished. No error reported.
[root@oraclevm /]#

Edit /boot/grub2/grub.cfg and replace root=/dev/mapper/ol-root with migrated disk UUID (root=UUID=35e305ec-c8d4-40f9-a9e8-98dc3b27f565)

Now mount the new disk.

[root@oraclevm ~]# mount /dev/nvme0n2p1 /tmp_boot/
[root@oraclevm ~]# mount /dev/nvme0n2p2 /tmp_os

Copy the updated /etc/default/grub and /boot/grub2/grub.cfg file to the new disk.

[root@oraclevm ~]# cp /etc/default/grub /tmp_os/etc/default/grub
cp: overwrite '/tmp_os/etc/default/grub'? y
[root@oraclevm ~]# cat /tmp_os/etc/default/grub
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rhgb quiet"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=false
[root@oraclevm ~]#

Updated /boot/grub2/grub.cfg and copy the same to new disk.

[root@oraclevm grub2]# cp grub.cfg /tmp_boot/grub2/grub.cfg
cp: overwrite '/tmp_boot/grub2/grub.cfg'? y
[root@oraclevm grub2]#

Update /etc/fstab and copy the same.

[root@oraclevm /]# cat /etc/fstab | grep -v "^#"
UUID=35e305ec-c8d4-40f9-a9e8-98dc3b27f565     /                       xfs     defaults        0 0
UUID=bb83e8cd-16ad-4aff-a3f4-4a9505d9b5ca /boot                   xfs     defaults        0 0
[root@oraclevm /]#

[root@oraclevm /]# cp /etc/fstab /tmp_os/etc/fstab
cp: overwrite '/tmp_os/etc/fstab'? y
[root@oraclevm /]#


Reboot the server.

[root@oraclevm ~]# uptime
 15:27:10 up 1 min,  1 user,  load average: 0.52, 0.24, 0.09
[root@oraclevm ~]# cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-5.4.17-2136.307.3.1.el8uek.x86_64 root=UUID=35e305ec-c8d4-40f9-a9e8-98dc3b27f565 ro rhgb quiet
[root@oraclevm ~]#

[root@oraclevm ~]# df -TH  | grep -i xfs
/dev/nvme0n2p2 xfs        21G   12G  9.1G  56% /
/dev/nvme0n2p1 xfs       1.1G  311M  754M  30% /boot
[root@oraclevm ~]#

We were successfully able to boot from migrated disk. Lets remove the old disk.

[root@oraclevm ~]# uptime
 15:29:58 up 1 min,  1 user,  load average: 0.79, 0.29, 0.11

[root@oraclevm ~]# fdisk -l
Disk /dev/nvme0n1: 20 GiB, 21474836480 bytes, 41943040 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x25d7b68c

Device         Boot   Start      End  Sectors Size Id Type
/dev/nvme0n1p1 *       2048  2099199  2097152   1G 83 Linux
/dev/nvme0n1p2      2099200 41943039 39843840  19G 83 Linux
[root@oraclevm ~]#

Dont get confuse with the name as /dev/nvme0n1. udev has renamed (/dev/nvme0n2 to /dev/nvme0n1) the disk name post removal of Original disk.





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