Linux Rescue System

Rescue is a Debian live system that boots from the network into RAM. It does not use your disks until you mount them or run installimage. Use it when the OS will not boot, when you forgot root, or when you want a clean install.

What Rescue is

Hetzner starts Rescue with PXE (network boot). Your NVMe or SATA drives sit idle. That is why Rescue can repair a broken system without writing to it. The environment is Debian-based. You can install extra tools with apt while Rescue is running.

Important note

Rescue is valid for one boot, and only for about 60 minutes after you click Activate. If you do not reboot in time, the next boot uses the installed OS again. Activate Rescue every time you need it.

Activate and boot

Open Robot → Servers → your server → Rescue.
Choose Linux, 64-bit. Add an SSH key if you have one. Activate.
Copy the temporary root password Robot shows you.
Reboot. If you still have SSH: reboot. If not: Robot → Reset → hardware reset.
Wait a minute, then SSH:

Log into Rescue

you@laptop ~ % ssh root@YOUR.SERVER.IP# oryou@laptop ~ % ssh -p 222 root@YOUR.SERVER.IP

You should see a banner like “Welcome to the Hetzner Rescue System”. The prompt looks like root@rescue, not your hostname.

Look before you touch disks

See disks, RAID, and LVM

root@rescue ~ # lsblkroot@rescue ~ # cat /proc/mdstatroot@rescue ~ # ls /dev/mapper/

If lsblk shows TYPE values like raid1 and names like md0, you have software RAID. If you only see sda / nvme0n1 partitions, there is no software RAID.

You see	Meaning	Usual root device
`md0`, `md1`, `md2`	Software RAID	Often `/dev/md2`
`vg0-root`	LVM on top of a disk or RAID	`/dev/mapper/vg0-root`
`sda3` only	Plain partitions	Often the last big partition

Mount the installed system

Mounting is “plug this filesystem into a folder”. Rescue uses /mnt as that folder.

Software RAID root

root@rescue ~ # mount /dev/md2 /mnt

LVM root

root@rescue ~ # mount /dev/mapper/vg0-root /mnt

Plain disk root

root@rescue ~ # mount /dev/sda3 /mnt

For a full chroot you also need boot, EFI, and pseudo filesystems. Hetzner Rescue includes a helper:

Enter the installed OS from Rescue

root@rescue ~ # chroot-prepare /mntroot@rescue ~ # chroot /mntroot@rescue ~ # passwdroot@rescue ~ # exit

Tip

passwd inside the chroot changes the installed system’s root password, not the Rescue password.

Install or reinstall an OS

From Rescue, run Hetzner’s installer. It wipes the drives you select:

Start the installer menu

root@rescue ~ # installimage

Pick Ubuntu or Debian, edit the config in Midnight Commander, save with F10 (or Esc then 0 if F10 prints garbage). Details and example configs are on the Ubuntu & Debian page.

Destructive

If an OS is already on software RAID, stop the arrays and wipe signatures before a new install, or the new system may not boot.

Clear old RAID and partition signatures

root@rescue ~ # mdadm --stop /dev/md*root@rescue ~ # wipefs -fa /dev/sd*root@rescue ~ # wipefs -fa /dev/nvme*n1

Hardware RAID first

If Robot or lspci shows a hardware RAID card, build the virtual disk in the controller BIOS / Hetzner tools before installimage. Software RAID (mdadm) is more common on auction servers with two plain NVMe or SATA drives.