How to activate rescue mode on a Public Cloud instance

Objective

Your Public Cloud instance may become inaccessible due to a lost SSH key or configuration errors.

In such circumstances, you can use the rescue mode to reconfigure your instance or to recover your data.

This guide explains how to restart your OVHcloud Public Cloud instance into rescue mode and access your files.

Requirements

• A Public Cloud instance in your OVHcloud account
• Access to the OVHcloud Control Panel

Instructions

Step 1: Activating rescue mode

Log in to the OVHcloud Control Panel, go to the Public Cloud section and select the Public Cloud project concerned. Then click on Instances in the left-hand menu.

Click on ... in the row of the instance concerned and select Reboot in rescue mode.

You will now see the Reboot in rescue mode dialog box. Click the drop-down list to select the distribution you would like to use in rescue mode and then click the Restart button.

Once your instance has been rebooted in rescue mode, an information box will display the available ways of access.

Your temporary rescue mode password will only be shown in the VNC console. Click on your instance in the table, then switch to the tab VNC console to retrieve it.

Step 2: Accessing your data

When rescue mode has been activated, your instance's data will be attached as an additional disk. You will now need to mount it, by taking the following steps.

Establish an SSH connection to your instance. Once you are connected, verify the available disks with this command:

lsblk

The result will look similar to the following example output:

NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTS
sda       8:0    0  2.9G  0 disk
└─sda1    8:1    0  2.9G  0 part /
sdb       8:16   0   25G  0 disk
├─sdb1    8:17   0   24G  0 part
├─sdb14   8:30   0    4M  0 part
├─sdb15   8:31   0  106M  0 part
└─sdb16 259:0    0  913M  0 part

In rescue mode, sda is the rescue mode disk and sda1 is the primary rescue partition mounted on /.

In this example, the primary disk is sdb and the system partition is sdb1 (indicated by the size).

Mount this partition with the following command:

mount /dev/sdb1 /mnt/

Your data will now be accessible from the /mnt folder.

Step 3: Deactivating rescue mode

Once you have completed your tasks, you can deactivate rescue mode by rebooting your instance from the Control Panel interface. To execute this, click on ... and select Exit rescue mode.

Activating rescue mode using the OpenStack API

You can also activate rescue mode via the OpenStack API using the following command:

nova rescue INSTANCE_ID

To exit rescue mode, use the following command:

nova unrescue INSTANCE_ID

Go further

How to replace an SSH key pair on an instance

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