Fix unreachable Ubuntu Noble Instances following a reboot

The newest Ubuntu 24.04 Noble Numbat Instances may become unreachable after a reboot. This distribution now uses dhcpcd which may encounter longer delays to reapply its DHCP lease after a reboot.

Instances created after June 11th 2024 will not encounter this problem.

Your Instance has not been rebooted

You can avoid this situation by increasing the dhcpcd timeout in its configuration file

sed -i 's/timeout 5/timeout 10/' /etc/dhcpcd.conf
tail /etc/dhcpcd.conf
option rapid_commit
# A ServerID is required by RFC2131.
require dhcp_server_identifier
# Generate SLAAC address using the Hardware Address of the interface
#slaac hwaddr
# OR generate Stable Private IPv6 Addresses based from the DUID
slaac private
timeout 10

Your Instance has rebooted and is no longer reachable

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.

1. Switch the Instance’s boot-type to rescue and reboot your Instance into rescue mode using the CLI:

   scw instance server stop <Instance_ID>
   scw instance server update <Instance_ID> boot-type=rescue
   scw instance server start <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
   

3. Once mounted, use the chroot command to get into your Instance’s root filesystem. You can then change the timeout value for dhcpcd as shown above :

   chroot /mnt
   sed -i 's/timeout 5/timeout 10/' /etc/dhcpcd.conf
   tail /etc/dhcpcd.conf
   option rapid_commit
   # A ServerID is required by RFC2131.
   require dhcp_server_identifier
   # Generate SLAAC address using the Hardware Address of the interface
   #slaac hwaddr
   # OR generate Stable Private IPv6 Addresses based from the DUID
   slaac private
   timeout 10
   exit
   umount /mnt
   

4. Switch back the Instance’s boot_type to local and reboot the Instance:

   scw instance server stop <Instance_ID>
   scw instance server update <Instance_ID> boot-type=local
   scw instance server start <Instance_ID>
   

   Once rebooted, your Instance will be reachable again.