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환경

• Red Hat Enterprise Linux 7
• Red Hat Virtualization if RHEL 7 is used as the virtualization host
• Red Hat Virtualization (RHV) 4.3

문제

• On a RHEL 7 host, using libguestfs utilities such as guestfish, virt-sysprep, or virt-customize to access or modify a RHEL 8 virtual disk image fails if the disk image is using an XFS or ext4 file system.

• For example:

Raw

# /usr/bin/virt-sysprep -a RHEL8.img [' [ 0.0] Examining the guest ... virt-sysprep: warning: mount_options: mount exited with status 32: mount: wrong fs type, bad option, bad superblock on /dev/mapper/rhel-root, missing codepage or helper program, or other error', ' In some cases useful info is found in syslog - try dmesg | tail or so. (ignored)', 'virt-sysprep: warning: mount_options: mount: /boot: mount point is not a directory (ignored) [ 15.5] Performing "abrt-data" ...']

• In RHV 4.3, it is not possible to create a template of RHEL8 guest due to this behavior

해결

There are two possible workarounds:

1. If viable, you can re-create the guest file systems and disable RHEL 8 file-system features that are incompatible with RHEL 7. To do so, use the mkfs utility with one of the following options:

   • For XFS file systems, use the -m reflink=0 option.
   • For ext4 file systems, use the -O ^metadata_csum option.
   • This is documented in this article.
   • Note that on a RHEL 8 host, the affected utilities work as expected.

2. Disclaimer: this workaround is unsupported - use the upstream latest libguestfs appliance.

   1. Download the latest upstream libguestfs appliance on RHEL-7 host:

      Raw

      [RHEL7.6-host]$ pwd /export [RHEL7.6-host]$ wget \ http://download.libguestfs.org/binaries/appliance/appliance-1.38.0.tar.xz

   2. Extract the upstream appliance and enumerate its content, also, make sure that qemu has access to the files:

      Raw

      [RHEL7.6-host]$ tar -Jxf appliance-1.38.0.tar.xz [RHEL7.6-host]$ ls /export/appliance initrd kernel README.fixed root [RHEL7.6-host]$ chmod -R a+rwX /export/applicance

   3. Set the LIBGUESTFS_PATH variable to the above appliance:

      Raw

      [RHEL7.6-host]$ export LIBGUESTFS_PATH=/export/appliance

   4. Validate

      • Read-only mount the RHEL-8 disk image via guestfish, and read the /etc/redhat-release file:

        Raw

        [RHEL7.6-host]$ guestfish --ro -i \ -a rhel-guest-image-8.0-1590.x86_64.qcow2 Welcome to guestfish, the guest filesystem shell for editing virtual machine filesystems and disk images. Type: ‘help’ for help on commands ‘man’ to read the manual ‘quit’ to quit the shell Operating system: Red Hat Enterprise Linux 8.0 Beta (Ootpa) /dev/sda3 mounted on / /dev/sda1 mounted on /boot ><fs> cat /etc/redhat-release Red Hat Enterprise Linux release 8.0 Beta (Ootpa)

      • Or, remove the root password via virt-edit (or reset it via virt-sysprep — refer further below):

        Raw

        [RHEL7.6-host]$ virt-edit \ -a rhel-guest-image-8.0-1590.x86_64.qcow2 \ /etc/passwd -e 's/^root:.*?:/root::/'

      • Or, uninstall the ‘cloud-init’ RPM:

        Raw

        [RHEL7.6-host]$ virt-customize --uninstall cloud-init \ -a rhel-guest-image-8.0-1590.x86_64.qcow2

      • Or just cat a file

        Raw

        [RHEL7.6-host]$ virt-cat -a rhel-guest-image-8.0-1590.x86_64.qcow2 /var/log/cloud-init.log > cloud-init.log

근본 원인

RHEL 7 is not fully compatible with certain features of the XFS and ext4 file systems in RHEL 8, based on RH Private BZ#1667478.
RHV BZ 1671895.