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Chroot environment in a Linux rescue VM

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Applies to: ✔️ Linux VMs

Note

CentOS referenced in this article is a Linux distribution and will reach End Of Life (EOL). Consider your use and plan accordingly. For more information, see CentOS End Of Life guidance.

This article describes how to troubleshoot the chroot environment in the rescue virtual machine (VM) in Linux.

Ubuntu 16.x && Ubuntu 18.x && Ubuntu 20.04

  1. Stop or deallocate the affected VM.

  2. Create a rescue VM of the same generation, same OS version, in same resource group and location using managed disk.

  3. Use the Azure portal to take a snapshot of the affected virtual machine's OS disk.

  4. Create a disk out of the snapshot of the OS disk, and attach it to the rescue VM.

  5. Once the disk has been created, troubleshoot the chroot environment in the rescue VM.

    1. Access your VM as the root user by using the following command:

      sudo su -

    2. Find the disk using dmesg (the method you use to discover your new disk may vary). The following example uses dmesg to filter on Small Computer Systems Interface (SCSI) disks:

      dmesg | grep SCSI

      The command output is similar to the following example. In this example, the /dev/sdc disk is what you want:

      [    0.294784] SCSI subsystem initialized
[    0.573458] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
[    7.110271] sd 2:0:0:0: [sda] Attached SCSI disk
[    8.079653] sd 3:0:1:0: [sdb] Attached SCSI disk
[ 1828.162306] sd 5:0:0:0: [sdc] Attached SCSI disk

    3. Use the following commands to access the chroot environment:

      mkdir /rescue
mount /dev/sdc1 /rescue
mount /dev/sdc15 /rescue/boot/efi

mount -t proc /proc /rescue/proc
mount -t sysfs /sys /rescue/sys
mount -o bind /dev /rescue/dev
mount -o bind /dev/pts /rescue/dev/pts
mount -o bind /run /rescue/run
chroot /rescue

    4. Troubleshoot the chroot environment.

    5. Use the following commands to exit the chroot environment:

      exit

umount /rescue/proc/
umount /rescue/sys/
umount /rescue/dev/pts
umount /rescue/dev/
umount /rescue/run
cd /
umount /rescue/boot/efi
umount /rescue

      Note

      If you receive the error message "unable to unmount /rescue," add the -l option to the umount command, for example, umount -l /rescue.

  6. Detach the disk from the rescue VM and perform a disk swap with the original VM.

  7. Start the original VM and check its connectivity.

RHEL/Centos/Oracle 6.x && Oracle 8.x && RHEL/Centos 7.x with RAW Partitions

  1. Stop or deallocate the affected VM.

  2. Create a rescue VM image of the same OS version in the same resource group (RSG) and location using a managed disk.

  3. Use the Azure portal to take a snapshot of the affected virtual machine's OS disk.

  4. Create a disk out of the snapshot of the OS disk, and attach it to the rescue VM.

  5. Once the disk has been created, troubleshoot the chroot environment in the rescue VM.

    1. Access your VM as the root user by using the following command:

      sudo su -

    2. Find the disk using dmesg (the method you use to discover your new disk may vary). The following example uses dmesg to filter on SCSI disks:

      dmesg | grep SCSI

      The command output is similar to the following example. In this example, the /dev/sdc disk is what you want:

      [    0.294784] SCSI subsystem initialized
[    0.573458] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
[    7.110271] sd 2:0:0:0: [sda] Attached SCSI disk
[    8.079653] sd 3:0:1:0: [sdb] Attached SCSI disk
[ 1828.162306] sd 5:0:0:0: [sdc] Attached SCSI disk

    3. Use the following commands to access the chroot environment:

      mkdir /rescue
mount -o nouuid /dev/sdc2 /rescue
mount -o nouuid /dev/sdc1 /rescue/boot/

mount -t proc /proc /rescue/proc
mount -t sysfs /sys /rescue/sys
mount -o bind /dev /rescue/dev
mount -o bind /dev/pts /rescue/dev/pts
mount -o bind /run /rescue/run
chroot /rescue

    4. Troubleshoot the chroot environment.

    5. Use the following commands to exit the chroot environment:

      exit

umount /rescue/proc/
umount /rescue/sys/
umount /rescue/dev/pts
umount /rescue/dev/
umount /rescue/run
cd /
umount /rescue/boot/
umount /rescue

      Note

      If you receive the error message "unable to unmount /rescue," add the -l option to the umount command, for example, umount -l /rescue.

  6. Detach the disk from the rescue VM and perform a disk swap with the original VM.

  7. Start the original VM and check its connectivity.

RHEL/Centos 7.x & 8.X with LVM

Note

If your original VM includes Logical Volume Manager (LVM) on the OS Disk, create the rescue VM by using the image with raw partitions on the OS Disk.

  1. Stop or deallocate the affected VM.

  2. Create a rescue VM image of the same OS version in the same resource group (RSG) and location using a managed disk.

  3. Use the Azure portal to take a snapshot of the affected virtual machine's OS disk.

  4. Create a disk out of the snapshot of the OS disk, and attach it to the rescue VM.

  5. Once the disk has been created, troubleshoot the chroot environment in the rescue VM.

    1. Access your VM as the root user by using the following command:

      sudo su -

    2. Find the disk using dmesg (the method you use to discover your new disk may vary). The following example uses dmesg to filter on SCSI disks:

      dmesg | grep SCSI

      The command output is similar to the following example. In this example, the /dev/sdc disk is what you want:

      [    0.294784] SCSI subsystem initialized
[    0.573458] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
[    7.110271] sd 2:0:0:0: [sda] Attached SCSI disk
[    8.079653] sd 3:0:1:0: [sdb] Attached SCSI disk
[ 1828.162306] sd 5:0:0:0: [sdc] Attached SCSI disk

    3. Use the following commands to activate the logical volume group:

      vgscan --mknodes
vgchange -ay
lvscan

    4. Use the lsblk command to retrieve the LVM names:

      lsblk

      NAME              MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                 8:0    0   64G  0 disk
├─sda1              8:1    0  500M  0 part /boot
├─sda2              8:2    0   63G  0 part /
sdb                 8:16   0    4G  0 disk
└─sdb1              8:17   0    4G  0 part /mnt/resource
sdc                 8:0    0   64G  0 disk
├─sdc1              8:1    0  500M  0 part
├─sdc2              8:2    0   63G  0 part
├─sdc3              8:3    0    2M  0 part
├─sdc4              8:4    0   63G  0 part
  ├─rootvg-tmplv  253:0    0    2G  0 lvm  
  ├─rootvg-usrlv  253:1    0   10G  0 lvm  
  ├─rootvg-optlv  253:2    0    2G  0 lvm  
  ├─rootvg-homelv 253:3    0    1G  0 lvm  
  ├─rootvg-varlv  253:4    0    8G  0 lvm  
  └─rootvg-rootlv 253:5    0    2G  0 lvm

    5. Use the following commands to prepare the chroot dir:

      mkdir /rescue
mount /dev/mapper/rootvg-rootlv /rescue
mount /dev/mapper/rootvg-varlv /rescue/var
mount /dev/mapper/rootvg-homelv /rescue/home
mount /dev/mapper/rootvg-usrlv /rescue/usr
mount /dev/mapper/rootvg-tmplv /rescue/tmp
mount /dev/mapper/rootvg-optlv /rescue/opt
mount /dev/sdc2 /rescue/boot/
mount /dev/sdc1 /rescue/boot/efi

      The /rescue/boot/ and /rescue/boot/efi partitions may not always be located on /dev/sdc2 or /dev/sdc1. If you encounter an error while trying to mount these partitions, check the /rescue/etc/fstab file to determine the correct devices for the /boot and /boot/efi partitions from the broken OS disk. Then, run the blkid command and compare the Universal Unique Identifier (UUID) from the /rescue/etc/fstab file with the output of the blkid command to determine the correct device for mounting /rescue/boot/ and /rescue/boot/efi in the repair VM.

      The mount /dev/mapper/rootvg-optlv /rescue/opt command may fail if the rootvg-optlv volume group doesn't exist. In this case, you can bypass this command.

    6. Access the chroot environment by using the following commands:

      mount -t proc /proc /rescue/proc
mount -t sysfs /sys /rescue/sys
mount -o bind /dev /rescue/dev
mount -o bind /dev/pts /rescue/dev/pts
mount -o bind /run /rescue/run
chroot /rescue

    7. Troubleshoot the chroot environment.

    8. Use the following commands to exit the chroot environment:

      exit

umount /rescue/proc/
umount /rescue/sys/
umount /rescue/dev/pts
umount /rescue/dev/
umount /rescue/run
cd /
umount /rescue/boot/efi
umount /rescue/boot
umount /rescue/home
umount /rescue/var
umount /rescue/usr
umount /rescue/tmp
umount /rescue/opt
umount /rescue

      Note

      If you receive the error message "unable to unmount /rescue," add the -l option to the umount command, for example, umount -l /rescue.

  6. Detach the disk from the rescue VM and perform a disk swap with the original VM.

  7. Start the original VM and check its connectivity.

Using the same LVM image

Note

If you need to deploy the rescue VM by using the same LVM image, you need to modify some aspects of the rescue VM with LVM.

The following commands are to be executed on the recovery/rescue VM that's temporarily created for the recovery operation.

  1. Use the following command to check the status of the disks prior to attaching the disk you want to rescue:

    sudo lsblk -f

    NAME              FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1            vfat              93DA-8C20                              /boot/efi
├─sda2            xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sda3
└─sda4            LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─rootvg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─rootvg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─rootvg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─rootvg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─rootvg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─rootvg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /
sdb
└─sdb1            ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8   /mnt

  2. Attach the disk you want to rescue as a data drive.

  3. Check the disks again by using the following command:

    sudo lsblk -f

    NAME              FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1            vfat              93DA-8C20                              /boot/efi
├─sda2            xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sda3
└─sda4            LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─rootvg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─rootvg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─rootvg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─rootvg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─rootvg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─rootvg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /
sdb
└─sdb1            ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8   /mnt
sdc
├─sdc1            vfat              93DA-8C20
├─sdc2            xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d
├─sdc3
└─sdc4            LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU

    The command output doesn't show the LVM structures right away.

  4. View physical LVM partitions by using the following command:

    sudo pvs

    This output shows warnings about duplicated physical volumes (PVs):

    WARNING: Not using lvmetad because duplicate PVs were found.
WARNING: Use multipath or vgimportclone to resolve duplicate PVs?
WARNING: After duplicates are resolved, run "pvscan --cache" to enable lvmetad.
WARNING: Not using device /dev/sdc4 for PV pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU.
WARNING: PV pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU prefers device /dev/sda4 because device is used by LV.
PV         VG     Fmt  Attr PSize   PFree
/dev/sda4  rootvg lvm2 a--  <63.02g <38.02g

  5. Use the vmimportclone command to import the rootvg from the data drive by using another name.

    This command changes the UUID of the PV and and also activates it:

    sudo vgimportclone -n rescuemevg /dev/sdc4

    WARNING: Not using device /dev/sdc4 for PV <PV>.
WARNING: PV pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU prefers device /dev/sda4 because device is used by LV.

    sudo vgchange -a y rescuemevg 

    6 logical volume(s) in volume group "rescuemevg" now active

  6. Verify the name change by using the following command:

    sudo lsblk -f

    NAME                  FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1                vfat              93DA-8C20                              /boot/efi
├─sda2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sda3
└─sda4                LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─rootvg-tmplv      xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─rootvg-usrlv      xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─rootvg-optlv      xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─rootvg-homelv     xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─rootvg-varlv      xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─rootvg-rootlv     xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /
sdb
└─sdb1                ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8   /mnt
sdc
├─sdc1                vfat              93DA-8C20
├─sdc2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d
├─sdc3
└─sdc4                LVM2_member       BbZsAT-5oOK-nITn-bHFW-IVyS-y0O3-93oDes
├─rescuemevg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207
├─rescuemevg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d
├─rescuemevg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3
├─rescuemevg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0
├─rescuemevg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86
└─rescuemevg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809

  7. Rename the rootvg of the rescue VM by using the following command:

    sudo vgrename rootvg oldvg

    Volume group "rootvg" successfully renamed to "oldvg"

  8. Check the disks by using the following command:

    sudo lsblk -f

    NAME                  FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1                vfat              93DA-8C20                              /boot/efi
├─sda2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sda3
└─sda4                LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─oldvg-tmplv       xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─oldvg-usrlv       xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─oldvg-optlv       xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─oldvg-homelv      xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─oldvg-varlv       xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─oldvg-rootlv      xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /
sdb
└─sdb1                ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8   /mnt
sdc
├─sdc1                vfat              93DA-8C20
├─sdc2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d
├─sdc3
└─sdc4                LVM2_member       BbZsAT-5oOK-nITn-bHFW-IVyS-y0O3-93oDes
├─rescuemevg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207
├─rescuemevg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d
├─rescuemevg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3
├─rescuemevg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0
├─rescuemevg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86
└─rescuemevg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809

  9. Mount the file system that comes from the data drive.

    When using xfs, specify the -o nouuid option to avoid conflicts with the UUIDs and mount the needed file systems to perform a chroot. This option isn't available in ext4 file systems, so you need to remove it from the commands in such a scenario:

    sudo mkdir /rescue
sudo mount -o nouuid /dev/mapper/rescuemevg-rootlv /rescue
sudo mount -o nouuid  /dev/mapper/rescuemevg-homelv /rescue/home
sudo mount -o nouuid  /dev/mapper/rescuemevg-optlv /rescue/opt 
sudo mount -o nouuid  /dev/mapper/rescuemevg-tmplv /rescue/tmp 
sudo mount -o nouuid  /dev/mapper/rescuemevg-usrlv /rescue/usr 
sudo mount -o nouuid  /dev/mapper/rescuemevg-varlv /rescue/var 
sudo mount -o nouuid  /dev/sdc2 /rescue/boot
sudo mount /dev/sdc1 /rescue/boot/efi

sudo mount -t proc /proc /rescue/proc 
sudo mount -t sysfs /sys /rescue/sys
sudo mount -o bind /dev /rescue/dev 
sudo mount -o bind /dev/pts /rescue/dev/pts
sudo mount -o bind /run /rescue/run

    The /rescue/boot/ and /rescue/boot/efi partitions may not always be located on /dev/sdc2 or /dev/sdc1. If you encounter an error while trying to mount these partitions, check the /rescue/etc/fstab file to determine the correct devices for the /boot and /boot/efi partitions from the broken OS disk. Then, run the blkid command and compare the UUID from the /rescue/etc/fstab file with the output of the blkid command to determine the correct device for mounting /rescue/boot/ and /rescue/boot/efi in the repair VM. Duplicated UUIDs may appear in the output. In this scenario, mount the partition that matches the device letter from step 5. In the example of this section, the correct partition you should mount is /dev/sdc. The dev/sda represents the operating system currently in use and should be ignored.

  10. Verify the mounts by using the following command:

    sudo lsblk -f

    NAME                  FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1                vfat              93DA-8C20                              /boot/efi
├─sda2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sda3
└─sda4                LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─oldvg-tmplv       xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─oldvg-usrlv       xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─oldvg-optlv       xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─oldvg-homelv      xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─oldvg-varlv       xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─oldvg-rootlv      xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /
sdb
└─sdb1                ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8   /mnt
sdc
├─sdc1                vfat              93DA-8C20                              /rescue/boot/efi
├─sdc2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /rescue/boot
├─sdc3
└─sdc4                LVM2_member       BbZsAT-5oOK-nITn-bHFW-IVyS-y0O3-93oDes
├─rescuemevg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207   /rescue/tmp
├─rescuemevg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /rescue/usr
├─rescuemevg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /rescue/opt
├─rescuemevg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /rescue/home
├─rescuemevg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /rescue/var
└─rescuemevg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /rescue

  11. Use chroot by using the following command:

    sudo chroot /rescue/

  12. Verify the mounts "inside" the chroot environment by using the following command:

    sudo lsblk -f

    NAME                  FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1                vfat              93DA-8C20
├─sda2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d
├─sda3
└─sda4                LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─oldvg-tmplv       xfs               9098eb05-0176-4997-8132-9152a7bef207
├─oldvg-usrlv       xfs               2f9ff36c-742d-4914-b463-d4152801b95d
├─oldvg-optlv       xfs               aeacea8e-3663-4569-af25-c52357f8a0a3
├─oldvg-homelv      xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0
├─oldvg-varlv       xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86
└─oldvg-rootlv      xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809
sdb
└─sdb1                ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8
sdc
├─sdc1                vfat              93DA-8C20                              /boot/efi
├─sdc2                xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sdc3
└─sdc4                LVM2_member       BbZsAT-5oOK-nITn-bHFW-IVyS-y0O3-93oDes
├─rescuemevg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─rescuemevg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─rescuemevg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─rescuemevg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─rescuemevg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─rescuemevg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /

    Now, rescuemevg-rootlv is the one mounted on /.

  13. Rename the Volume Group (VG) to keep it consistent by using the following command. Renaming the VG keeps you from facing issues when regenerating the initrd and booting the disk again on the original VM.

    sudo vgrename rescuemevg rootvg

    Volume group "rescuemevg" successfully renamed to "rootvg"

  14. Verify the change by using the following command:

    sudo lsblk -f

    NAME              FSTYPE      LABEL UUID                                   MOUNTPOINT
sda
├─sda1            vfat              93DA-8C20
├─sda2            xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d
├─sda3
└─sda4            LVM2_member       pdSI2Q-ZEzV-oT6P-R2JG-ZW3h-cmnf-iRN6pU
├─oldvg-tmplv   xfs               9098eb05-0176-4997-8132-9152a7bef207
├─oldvg-usrlv   xfs               2f9ff36c-742d-4914-b463-d4152801b95d
├─oldvg-optlv   xfs               aeacea8e-3663-4569-af25-c52357f8a0a3
├─oldvg-homelv  xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0
├─oldvg-varlv   xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86
└─oldvg-rootlv  xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809
sdb
└─sdb1            ext4              e72e7c2c-db27-4a73-a97e-01d63d21ccf8
sdc
├─sdc1            vfat              93DA-8C20                              /boot/efi
├─sdc2            xfs               d5da486e-fdfe-4ad8-bc01-aa72b91fd47d   /boot
├─sdc3
└─sdc4            LVM2_member       BbZsAT-5oOK-nITn-bHFW-IVyS-y0O3-93oDes
├─rootvg-tmplv  xfs               9098eb05-0176-4997-8132-9152a7bef207   /tmp
├─rootvg-usrlv  xfs               2f9ff36c-742d-4914-b463-d4152801b95d   /usr
├─rootvg-optlv  xfs               aeacea8e-3663-4569-af25-c52357f8a0a3   /opt
├─rootvg-homelv xfs               a79e43dc-7adc-41b4-b6e1-4e6b033b15c0   /home
├─rootvg-varlv  xfs               c7cb68e9-7865-4187-b3bd-e9a869779d86   /var
└─rootvg-rootlv xfs               d8dc4d62-ada5-4952-a0d9-1bce6cb6f809   /

  15. Proceed with the required activities to rescue the OS. These activities may include regenerating initramfs or the GRUB configuration.

  16. Exit the chroot environment by using the following command:

    sudo exit

  17. Unmount and detach the data disk from the rescue VM and perform a disk swap with the original VM by using the following commands:

    umount /rescue/run/
umount /rescue/dev/pts/
umount /rescue/dev/ 
umount /rescue/sys/
umount /rescue/proc
umount /rescue/boot/efi
umount /rescue/boot
umount /rescue/var
umount /rescue/usr
umount /rescue/tmp
umount /rescue/opt
umount /rescue/home
umount /rescue

  18. Start the original VM and verify its functionality.

Oracle 7.x

  1. Stop or deallocate the affected VM.

  2. Create a rescue VM image of the same OS version, in the same resource group (RSG) and location using a managed disk.

  3. Use the Azure portal to take a snapshot of the affected virtual machine's OS disk.

  4. Create a disk out of the snapshot of the OS disk, and attach it to the rescue VM.

  5. Once the disk has been created, troubleshoot the chroot environment in the rescue VM.

    1. Access your VM as the root user by using the following command:

      sudo su -

    2. Find the disk by using dmesg (the method you use to discover your new disk may vary). The following example uses dmesg to filter on SCSI disks:

      dmesg | grep SCSI

      The command output is similar to the following example. In this example, the /dev/sdc disk is what you want:

      [    0.294784] SCSI subsystem initialized
[    0.573458] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
[    7.110271] sd 2:0:0:0: [sda] Attached SCSI disk
[    8.079653] sd 3:0:1:0: [sdb] Attached SCSI disk
[ 1828.162306] sd 5:0:0:0: [sdc] Attached SCSI disk

    3. Use the following commands to access the chroot environment:

      mkdir /rescue
mount -o nouuid /dev/sdc2 /rescue
mount -o nouuid /dev/sdc1 /rescue/boot/
mount /dev/sdc15 /rescue/boot/efi

mount -t proc /proc /rescue/proc
mount -t sysfs /sys /rescue/sys
mount -o bind /dev /rescue/dev
mount -o bind /dev/pts /rescue/dev/pts
mount -o bind /run /rescue/run
chroot /rescue

    4. Troubleshoot the chroot environment.

    5. Use the following commands to exit the chroot environment:

      exit

umount /rescue/proc/
umount /rescue/sys/
umount /rescue/dev/pts
umount /rescue/dev/
umount /rescue/run
umount /rescue/boot/efi
umount /rescue/boot
umount /rescue

      Note

      If you receive the error message "unable to unmount /rescue," add the -l option to the umount command, for example, umount -l /rescue.

  6. Detach the disk from the rescue VM and perform a disk swap with the original VM.

  7. Start the original VM and check its connectivity.

SUSE-SLES 12 SP4, SUSE-SLES 12 SP4 For SAP && ## SUSE-SLES 15 SP1, SUSE-SLES 15 SP1 For SAP

  1. Stop or deallocate the affected VM.

  2. Create a rescue VM image of the same OS version, in the same resource group (RSG) and location using a managed disk.

  3. Use the Azure portal to take a snapshot of the affected virtual machine's OS disk.

  4. Create a disk out of the snapshot of the OS disk, and attach it to the rescue VM.

  5. Once the disk has been created, troubleshoot the chroot environment in the rescue VM.

    1. Access your VM as the root user using the following command:

      sudo su -

    2. Find the disk using dmesg (the method you use to discover your new disk may vary). The following example uses dmesg to filter on SCSI disks:

      dmesg | grep SCSI

      The command output is similar to the following example. In this example, the /dev/sdc disk is what you want:

      [    0.294784] SCSI subsystem initialized
[    0.573458] Block layer SCSI generic (bsg) driver version 0.4 loaded (major 252)
[    7.110271] sd 2:0:0:0: [sda] Attached SCSI disk
[    8.079653] sd 3:0:1:0: [sdb] Attached SCSI disk
[ 1828.162306] sd 5:0:0:0: [sdc] Attached SCSI disk

    3. Use the following commands to access the chroot environment:

      mkdir /rescue
mount -o nouuid /dev/sdc4 /rescue
mount -o nouuid /dev/sdc3 /rescue/boot/
mount /dev/sdc2 /rescue/boot/efi

mount -t proc /proc /rescue/proc
mount -t sysfs /sys /rescue/sys
mount -o bind /dev /rescue/dev
mount -o bind /dev/pts /rescue/dev/pts
mount -o bind /run /rescue/run
chroot /rescue

    4. Troubleshoot the chroot environment.

    5. Use the following commands to exit the chroot environment:

      exit

umount /rescue/proc/
umount /rescue/sys/
umount /rescue/dev/pts
umount /rescue/dev/
umount /rescue/run
umount /rescue/boot/efi
umount /rescue/boot
umount /rescue

      Note

      If you receive the error message "unable to unmount /rescue," add the -l option to the umount command, for example, umount -l /rescue.

  6. Detach the disk from the rescue VM and perform a disk swap with the original VM.

  7. Start the original VM and check its connectivity.

Next Steps

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