curtin raises an error using the bcache storage layout

[Javier Fuentes]

Using bcache as storage layout raises an error during the deployment phase of a(n arm64) machine. Any other storage layout complete the deployment successfully without errors.

This has been observed consistently in 3 different machines, all arm64, deploying Ubuntu 22 and 20. The MAAS installation used is snap for the version 3.2.

The error reported in the machine installation logs ("Installation output" tab) is as follows:

'''
        Running command ['umount', '/tmp/tmptbdyj261/target/dev'] with allowed return codes [0] (capture=False)
        finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/install-grub: FAIL: installing grub to target devices
        finish: cmd-install/stage-curthooks/builtin/cmd-curthooks/configuring-bootloader: FAIL: configuring target system bootloader
        finish: cmd-install/stage-curthooks/builtin/cmd-curthooks: FAIL: curtin command curthooks
        Traceback (most recent call last):
          File "/curtin/curtin/commands/main.py", line 202, in main
            ret = args.func(args)
          File "/curtin/curtin/commands/curthooks.py", line 1886, in curthooks
            builtin_curthooks(cfg, target, state)
          File "/curtin/curtin/commands/curthooks.py", line 1851, in builtin_curthooks
            setup_grub(cfg, target, osfamily=osfamily,
          File "/curtin/curtin/commands/curthooks.py", line 804, in setup_grub
            install_grub(instdevs, target, uefi=uefi_bootable, grubcfg=grubcfg)
          File "/curtin/curtin/commands/install_grub.py", line 401, in install_grub
            in_chroot.subp(cmd, env=env, capture=True)
          File "/curtin/curtin/util.py", line 787, in subp
            return subp(*args, **kwargs)
          File "/curtin/curtin/util.py", line 275, in subp
            return _subp(*args, **kwargs)
          File "/curtin/curtin/util.py", line 139, in _subp
            raise ProcessExecutionError(stdout=out, stderr=err,
        curtin.util.ProcessExecutionError: Unexpected error while running command.
        Command: ['unshare', '--fork', '--pid', '--', 'chroot', '/tmp/tmptbdyj261/target', '/usr/lib/grub/grub-multi-install']
        Exit code: 1
        Reason: -
        Stdout: ''
        Stderr: Installing grub to /boot/efi.
                Installing for arm64-efi platform.
                Installation finished. No error reported.
                Installing grub to /var/lib/grub/esp.
                Installing for arm64-efi platform.
                grub-install: error: /var/lib/grub/esp doesn't look like an EFI partition.
'''

[Javier Fuentes (javier-fs)]

MAAS logs extracted from
  /var/snap/maas/common/log/maas.log
  /var/snap/maas/common/log/rackd.log
  /var/snap/maas/common/log/regiond.log

Other logs
  commissioning_script_c4mxmt.txt -> maas $ADMIN node-script-result download $SYSTEM_ID current-commissioning | tee <file>.txt

Configurations
  /var/snap/maas/32954/preseeds/curtin_userdata

Machine installation logs (downloaded through the "Download" button in the "Installation output" subtab in the "Logs" tab)
  installation output: sqa-lab2-infra-1-arm.maas-installation-output-2024-04-04.log
  curtin-logs: sqa-lab2-infra-1-arm.maas-curtin-2024-04-04.tar
  machine output (xml):sqa-lab2-infra-1-arm.maas-machine-output-2024-04-04.xml
  machine output (yaml): sqa-lab2-infra-1-arm.maas-machine-output-2024-04-04.yaml