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Troubleshooting issues with faulty kernel installations

Rescue mode allows you to boot your Instance into a temporary operating system, running from the Instance's RAM. Rescue mode is often used to diagnose and resolve issues such as faulty kernel configurations, networking issues, firewall configurations, and more.

Before you start

To complete the actions presented below, you must have:

  • A Scaleway account logged into the console
  • An Instance
  • Installed and configured the Scaleway CLI on your local computer
  1. Switch the Instance's boot-type to rescue and reboot your Instance into rescue mode using the CLI-Tools: 
    scw instance server update {Instance_ID} boot-type=rescue
scw instance server reboot {Instance_ID}
    Note

    Replace {Instance_ID} with the unique ID of your Instance, e.g. 0500ebd2-d70d-49af-a969-3ac09b6f7fff.

  2. Once the Instance is rebooted, log into your Instance using SSH and set up the environment to be able to chroot into it: 
    cat /proc/partitions
major minor #blocks name

8 0 9765625 sda
8 1 9634536 sda1
8 14 3072 sda14
8 15 126976 sda15
    Then mount the partitions: 
    mount /dev/sda1 /mnt
mount /dev/sda15 /mnt/boot/efi
mount -o bind /sys /mnt/sys
mount -o bind /proc /mnt/proc
mount -o bind /dev /mnt/dev
  3. Once mounted, use the chroot command to get into your Instances' root file system. You can then change the GRUB_DEFAULT value to boot using the previous kernel: 
    chroot /mnt
nano /etc/default/grub
    Tip

    In the example above, we use nano as text editor. Feel free to use your favorite text editor to edit the file.

    Change the value of GRUB_DEFAULT to `"1 > 2": 
    # head /etc/default/grub
# If you change this file, run 'update-grub' afterward to update
# /boot/grub/grub.cfg.
# For full documentation of the options in this file, see:
#   info -f grub -n 'Simple configuration'

GRUB_DEFAULT="1>2"
GRUB_TIMEOUT=5
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT=""
GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,115200 earlyprintk=ttyS0,115200 consoleblank=0"
    Save the file and exit the text editor.
  4. Update the grub boatloader` to apply the kernel's update: 
    # update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-6.0.0-0.deb11.2-cloud-amd64
Found initrd image: /boot/initrd.img-6.0.0-0.deb11.2-cloud-amd64
Found linux image: /boot/vmlinuz-5.19.0-0.deb11.2-cloud-amd64
Found initrd image: /boot/initrd.img-5.19.0-0.deb11.2-cloud-amd64
Found linux image: /boot/vmlinuz-5.10.0-19-cloud-amd64
Found initrd image: /boot/initrd.img-5.10.0-19-cloud-amd64
done
  5. Switch back the Instance's boot_type to local and reboot the Instance: 
    scw instance server update {Instance_ID} boot-type=local
scw instance server reboot {Instance_ID}
    Your Instance reboots on the previously installed kernel.

Examples of failed boots

  • In the following example, the Instance may only boot with the root file system in read-only mode: 
    [  OK  ] Finished Remove Stale Onli…ext4 Metadata Check Snapshots.
[    4.219158] cloud-init[542]: Traceback (most recent call last):
[    4.220328] cloud-init[542]:   File "/usr/bin/cloud-init", line 33, in <module>
[    4.221518] cloud-init[542]:     sys.exit(load_entry_point('cloud-init==20.4.1', 'console_scripts', 'cloud-init')())
[    4.223064] cloud-init[542]:   File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 891, in main
[    4.224435] cloud-init[542]:     retval = util.log_time(
[    4.225251] cloud-init[542]:   File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 2348, in log_time
[    4.226838] cloud-init[542]:     ret = func(*args, **kwargs)
[    4.227743] cloud-init[542]:   File "/usr/lib/python3/dist-packages/cloudinit/cmd/main.py", line 600, in status_wrapper
[    4.229478] cloud-init[542]:     util.ensure_dirs((data_d, link_d,))
[    4.230501] cloud-init[542]:   File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1534, in ensure_dirs
[    4.232014] cloud-init[542]:     ensure_dir(d, mode)
[    4.232540] cloud-init[542]:   File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1591, in ensure_dir
[    4.233980] cloud-init[542]:     chmod(path, mode)
[    4.234756] cloud-init[542]:   File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1830, in chmod
[    4.235672] cloud-init[542]:     os.chmod(path, real_mode)
[    4.236227] cloud-init[542]: OSError: [Errno 30] Read-only file system: '/var/lib/cloud/data'
[FAILED] Failed to start Apply the …ngs specified in cloud-config.
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