--- title: "How to activate and use rescue mode" description: "Learn how to reboot and use a server in rescue mode." url: https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/rescue-mode lang: en --- > For AI agents: the complete documentation index is available at https://docs.us.ovhcloud.com/en/llms.txt, the full documentation bundle is available at https://docs.us.ovhcloud.com/en/llms-full.txt. # How to activate and use rescue mode **Learn how to reboot and use a server in rescue mode.** Rescue mode is a tool provided by OVHcloud that allows you to boot into a temporary operating system to diagnose and resolve issues on your server. Usual tasks the rescue mode is appropriate for include: - Resetting your user password - Diagnosing network problems - Repairing a broken operating system - Fixing a software firewall misconfiguration - Testing disk performance - Testing CPU and RAM   ## Requirements - A [dedicated server](https://us.ovhcloud.com/bare-metal/) in your OVHcloud account - Access to the [OVHcloud Control Panel](https://manager.us.ovhcloud.com/)   ## Topics - [Activating rescue mode](#activating-rescue-mode) - [Accessing your server in rescue mode via SSH](#accessing-your-server-in-rescue-mode-via-ssh) - [Mounting partitions to access your files](#mounting-partitions-to-access-your-files) - [Link Aggregation configuration in rescue mode](#link-aggregation-configuration-in-rescue-mode) - [Exiting rescue mode](#exiting-rescue-mode) - [How to add a default authentication key for rescue mode](#how-to-add-a-default-authentication-key-for-rescue-mode) - [Legacy Windows rescue system (WinPE rescue mode)](#legacy-windows-rescue-system-winpe-rescue-mode) - [How to test Additional IP and vRack functionality in rescue mode](#how-to-test-additional-ip-and-vrack-functionality-in-rescue-mode)   ## Instructions To use rescue mode, you must edit the server's **Netboot** setting. Then the server has to be restarted.   ### Activating rescue mode Log in to your [OVHcloud Control Panel](https://manager.us.ovhcloud.com/), open the `Bare Metal Cloud` section, then `Dedicated servers`, and select your server from the list. In the **General information** box, click the _more options_ `...` button next **Boot** and select `Edit`.   #### 1: Rescue mode options On the page **Change the netboot**, select `Boot in rescue mode`. The available options for rescue mode depend on the server type and the **operating system** installed. - Customer rescue system (always available) - Rescue system for Windows (available for Windows servers) - [iPXE](https://ipxe.org/) / ipxe-shell (external open-source tool, always available) - [Legacy Windows rescue system](#legacy-windows-rescue-system-winpe-rescue-mode) (deprecated WinPE system, only relevant if your server does not meet the requirements for the current rescue system for Windows) **Note:** The instructions below will only cover the **customer rescue system**, the most commonly used option. Please refer to our [dedicated guide for a detailed explanation on using the rescue system for Windows](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/rescue-customer-windows.md). Select `Customer rescue system` in the drop-down menu.   #### 2: Authentication options The next choice determines the method of authentication for the SSH connection to the rescue mode system. This is mainly a matter of convenience since each rescue mode session is meant to be transitory and will be discarded once you reboot the server from its disk. - **Password authentication**: You will be sent login credentials via email. - **Key authentication**: You can use a public authentication key of your choice (compatible formats: `RSA`, `ECDSA`, `ED25519`). Click on the relevant tab for your connection method: ##### Password authentication Click `Password authentication`. The rescue mode notification email including its login details will be sent to the contact email address of your OVHcloud account. To use a different email address, enter it in the field `Send new login details to the following email address`. Click `Next`. ##### Key authentication Click `Authentication via SSH key`. You have two options: - Select a key from the drop-down menu. You need to have at least one [public key stored in the OVHcloud Control Panel](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/import-keys.md) already. - Manually copy the public key string and paste it into the field `Your Public SSH key`. To find out more about this topic, consult our [How to create and use keys for SSH authentication](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/create-use-authentication-keys-ssh-connections-ovhcloud-server.md) guide. **Tip:** You can add a default public key for the customer rescue system to a server via the OVHcloud API. See the [Go further section below](#go-further) for details. Click `Next`.   #### 3: Final steps to activate rescue mode In the **Summary** step, click `Confirm`. You should now have a notification regarding the **Netboot** setting in the `General information` tab. The final step is to restart the server. Click the _more options_ `...` button next to "Status" in the **Service status** box, then select `Restart`. Click `Confirm` in the pop-up window. This "hard reboot" will take a few minutes to complete. You can check the current status in the tab named `Tasks`. **Note:** After you have finished your actions in rescue mode, remember to change the **Netboot** setting back to `Boot from the hard disk` before restarting the server.   ### Accessing your server in rescue mode via SSH Once you have received the email informing you that rescue mode is enabled, you can log on to the rescue mode system and access your server. **Note:** Your SSH client will normally block the connection at first due to a mismatch of the ECDSA fingerprint. This is normal because the rescue mode uses its own temporary SSH server. To resolve this, you need to edit the file `known_hosts` of your local `.ssh` folder.\ You have two options: - **Delete the fingerprint from the file.** Your SSH client will then add a new fingerprint entry for the server when you are no longer using rescue mode. For a detailed explanation, refer to our [SSH introduction guide](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/ssh-introduction.md). - **Temporarily disable the fingerprint.** Open the file `known_hosts` with a text editor and identify the fingerprint string of your server by its IP address. Add the character `#` at the start of the line. As a result, this line is now a "comment" and will be ignored by applications reading the file. Remember to revert this change before switching the `Netboot` back to the "normal" mode. Click on the relevant tab for your selected connection method: #### Password authentication Open the command line application on your local device and enter the following command: ```bash ssh root@SERVER_IP ``` Example: ```bash ssh root@203.0.113.100 ``` Enter the temporary rescue mode password when prompted. ``` root@ns9356771.ip-203-0-113.us's password: root@rescue-customer-us (ns9356771.ip-203-0-113.us) ~ # ``` Find more information about SSH connections in our [SSH introduction guide](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/ssh-introduction.md). #### Key authentication Open the command line application on your local device and enter the following command: ```bash ssh -i USER_FOLDER/.ssh/KEY_FILE_NAME root@SERVER_IP ``` Example: ```bash ssh -i ~/.ssh/MyAuthKey root@203.0.113.100 ``` If prompted, enter your password to decrypt the private key file. To learn more about this topic, consult our [How to create and use keys for SSH authentication](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/create-use-authentication-keys-ssh-connections-ovhcloud-server.md) guide.   ### Mounting partitions to access your files Unless you intend to configure the server's disks in a way that requires them to be detached (unmounted), you need to first **mount the system partition** in order to access your data from rescue mode. Firstly, list all partitions to retrieve the name of the partition you need to mount: ```bash lsblk ``` Output examples: ``` NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sda 8:0 0 1.8T 0 disk ├─sda1 8:1 0 511M 0 part ├─sda2 8:2 0 1.8T 0 part │ └─md127 9:127 0 1.8T 0 raid1 ├─sda3 8:3 0 512M 0 part └─sda4 8:4 0 2M 0 part sdb 8:16 0 1.8T 0 disk ├─sdb1 8:17 0 511M 0 part ├─sdb2 8:18 0 1.8T 0 part │ └─md127 9:127 0 1.8T 0 raid1 └─sdb3 8:19 0 512M 0 part ``` ``` NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT nvme1n1 259:0 0 894.3G 0 disk ├─nvme1n1p1 259:2 0 511M 0 part ├─nvme1n1p2 259:3 0 1G 0 part │ └─md2 9:2 0 1022M 0 raid1 ├─nvme1n1p3 259:4 0 892.3G 0 part │ └─md3 9:3 0 892.1G 0 raid1 └─nvme1n1p4 259:5 0 512M 0 part nvme0n1 259:1 0 894.3G 0 disk ├─nvme0n1p1 259:6 0 511M 0 part ├─nvme0n1p2 259:7 0 1G 0 part │ └─md2 9:2 0 1022M 0 raid1 ├─nvme0n1p3 259:8 0 892.3G 0 part │ └─md3 9:3 0 892.1G 0 raid1 ├─nvme0n1p4 259:9 0 512M 0 part └─nvme0n1p5 259:10 0 2M 0 part ``` Then mount the pertinent partition accordingly: ```bash mount /dev/PARTITION_NAME /MOUNT_POINT/ ``` The partition to mount should be easily identifiable by the **SIZE** indicated in the table (`sda2` in the first example, `nvme1n1p3` in the second). Using the folder name `mnt` as mount point, for the first example the `mount` command would therefore be as follows: ```bash mount /dev/md127 /mnt/ ``` Command to enter for the second example: ```bash mount /dev/md3 /mnt/ ``` **Warning:** **NOTE:** The examples above illustrate the necessary steps based on a typical server configuration. The information in the output table depends on your server's hardware and its partition scheme. When in doubt, consult the documentation of your operating system. If you require professional assistance with server administration, consider the details in the [Go further](#go-further) section of this guide. To see more technical information about the server's disks and partitions, enter: ```bash fdisk -l ``` Some tasks may require that disks or partitions be detached. To do this, use the unmount command: ```bash umount /mnt ``` **Warning:** **NOTE:** For password reset instructions, see the guides below: - [For Windows](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/reset-administrator-password-windows-server.md) - [For Linux](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/replacing-user-password.md)   #### VMware - Mounting a datastore You can mount a VMware datastore in a similar way as described in the previous segment. ##### Click here for the full instructions. List your partitions in order to retrieve the name of the datastore partition: ```bash lsblk ``` ```bash fdisk -l ``` Mount the partition with the following command, replacing `sdbX` with the value identified in the previous step: ```bash vmfs-fuse /dev/sdbX /mnt ``` If you have `VMFS 6` datastores, access the `sbin` folder and create the mount folder: ```bash cd /usr/local/sbin/ mkdir /mnt/datastore ``` List your partitions to retrieve the name of the datastore partition: ```bash lsblk ``` ```bash fdisk -l ``` Mount the partition with the following command, replacing `sdbX` with the value identified in the previous step: ```bash vmfs6-fuse /dev/sdbX /mnt/datastore/ ``` Once the mounting operation is done, you can access your files and carry out troubleshooting tasks inside the folder you have defined as mount point. Example: ```bash cd /mnt ``` Certain operations on the file system (such as configuring user accounts) will require an additional step. Create a temporary `chroot` environment at the mount point with this command: ```bash chroot /mnt/ ``` You should now be able now apply all necessary changes to your system.   ### Link Aggregation configuration in rescue mode Link Aggregation (LACP) is highly beneficial, as it increases your server's total bandwidth while providing network redundancy in case a network interface fails. Although rescue mode is based on the Debian 12 operating system, its network configuration relies on the `ifupdown` utility, instead of `Netplan`. If you have a server that supports link aggregation and you wish to configure it in rescue mode, please refer to [this guide](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/configure-ovhcloud-link-aggregation-dedicated-server-debian.md).   ### Exiting rescue mode If relevant, return to the rescue mode login shell by entering: ```bash exit ``` In your [OVHcloud Control Panel](https://manager.us.ovhcloud.com/), [change the boot mode](#1-rescue-mode-options) back to `Boot from the hard disk` and confirm. You can now restart the server from the rescue mode shell: ```bash reboot ``` Alternatively, use the `Restart` function in the OVHcloud Control Panel.   ### How to add a default authentication key for rescue mode To speed up the process, you can add a public key as default for rescue mode SSH access to your server. This is only possible via the [OVHcloud API](https://docs.us.ovhcloud.com/en/manage-and-operate/api/first-steps.md). #### Click here for the full instructions. To do this in the API web console, open the following API endpoint: [PUT /dedicated/server/{serviceName}](https://api.us.ovhcloud.com/console/?section=/dedicated/server&branch=v1#put-/dedicated/server/-serviceName-) Enter the internal name of your server (`ns1111111.ip-203-0-113.us`) in the appropriate field. Then edit the text field below as follows: ```bash { "rescueSshKey": "string" } ``` Replace `string` with your full public key string. The result should look as shown in the following example: When you have entered your values correctly, click the button `EXECUTE`. The field `Your Public SSH key:` will now be filled automatically with this key string when [changing the Netboot mode](#1-rescue-mode-options).   ### Legacy Windows rescue system (WinPE rescue mode) Once you have received the email informing you that rescue mode is enabled, you can log on to the rescue mode system and access your server. #### Click here for the full instructions. To use the Windows PE rescue mode GUI, you will need to download and install a VNC console or use the [IPMI module](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/use-ipmi-console.md) (not available on all server models). The following tools are already installed in this mode: | Tool | Description | | ----------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | Mozilla ULight | A web browser. | | Memory Diagnostics Tool | A Windows tool to test the RAM. | | Explorer\_Q-Dir | An alternative file explorer. | | GSmartControl | A tool to check HDDs and SSDs. | | PhotoRec | A tool to recover possibly lost files from a disk. | | SilverSHielD | A SSH2 and SFTP server. | | System Recovery | The built-in Windows system restore and troubleshooting tool. | | TestDisk | A powerful data recovery application. You can use it to recover and modify corrupted partitions, find lost partitions, repair a boot sector and even rebuild a defective MBR. | | FileZilla | An open-source FTP client. It supports SSH and SSL protocols, and has a clear and intuitive drag-and-drop interface. You can use it to transfer your data to an FTP server, like the FTP backup service included with most OVHcloud server models. | | 7-Zip | A utility for compressing and archiving files, which reads the following formats: ARJ, CAB, CHM, CPIO, CramFS, DEB, DMG, FAT, HFS, ISO, LZH, LZMA, MBR, MSI, NSIS, NTFS, RAR, RPM, SquashFS, UDF, VHD, WIM, XAR and Z. You can also use it to create your own archives in the following formats: BZIP2, GZIP, TAR, WIM, XZ, Z and ZIP. |   #### How to test Additional IP and vRack functionality in rescue mode **Testing Additional IPs** ##### Configured as an alias (without vMAC) To begin, put your server into rescue mode as described above. Once you are in rescue mode, use the following command to identify your NIC. ``` ip a ``` To find the correct NIC in your output, find the NIC that has your server's public IP address attached. In this article, we use the example interface `eth0`. We will add our additional IP to the interface using the following command. Be sure to replace our example values with yours. ``` ip addr add 203.0.113.1/32 dev eth0 ``` To test that your additional IP is functioning properly, ping it from a separate machine. If you are concerned that you are having routing issues, you can perform an mtr (My traceroute) test. In our example, we use an OpenDNS server. Be sure to replace our example values with yours. ``` mtr -rbwz 208.67.222.222 -a 203.0.113.1 ``` If you determine that you have routing issues, send the outputs of the following tests to OVHcloud US Support. ``` ip a ip r mtr -rbwz 208.67.222.222 -a 203.0.113.1 ``` ##### Bridge configuration (with vMAC) For a bridge configuration, the above steps will work with one modification. To add our additional IP to the interface, we will use the following four commands instead of the `ip addr add` command used above. In our example, we name our test link "testrescue." Be sure to replace our example values with yours. If you need help finding your Virtual MAC, check out the following article: [How to Assign a Virtual MAC to an Additional IP](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/network-virtual-mac.md) ``` ip link add name testrescue link eth0 type macvlan ip link set dev testrescue address 00:53:00:00:00:00 ip link set testrescue up ip addr add 203.0.113.1 dev testrescue ```   **Testing vRack** **Warning:** **NOTE:** Before testing your vRack connection, make sure both of the servers you use are on the same vRack. To begin testing that your vRack connection works, put two servers into rescue mode. Once you have gained access to rescue mode, we will configure both servers. We will use the same configuration on both servers, but with different private IP addresses. First, find your private interface using the following command: ``` ip a ``` Next, we will set our network configuration. To do so, open the interface file using the following command. ``` vim /etc/network/interfaces ``` Below is a sample configuration for this file. Make sure the private IPs you use on both servers are on the same subnet. ``` interfaces(5) file used by ifup(8) and ifdown(8) Include files from /etc/network/interfaces.d: source-directory /etc/network/interfaces.d auto eth1 iface eth1 inet static address 192.168.70.5 netmask 255.255.255.0 gateway 192.168.70.254 ``` Once you have configured both servers, ping one server from the other. If it works, you know you have a working vRack. If it does not, contact OVHcloud US support and send them the configuration files and results of your failed ping test.   ## Go further [How to activate and use Windows rescue mode](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/rescue-customer-windows.md) [How to recover server access if your user password is lost](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/replacing-user-password.md) [How to replace your authentication keys for SSH access if a key is lost](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/replacing-lost-ssh-key-pair.md) [How to diagnose server hardware issues](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/hardware-diagnostics-dedicated-server.md) [How to use the IPMI console with a dedicated server](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/use-ipmi-console.md) Browse all the [Dedicated Servers guides](https://docs.us.ovhcloud.com/en/bare-metal-cloud/dedicated-servers/landing-page-dedicated-servers.md). Browse the rest of the [OVHcloud US documentation](https://docs.us.ovhcloud.com/en/index.md) for guides on our other products and services. Learn more about [Dedicated Servers](https://us.ovhcloud.com/bare-metal/) on the OVHcloud US website.