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Debian installer rescue mode

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Some notes on having access to Debian installer in rescue mode in physical servers of WMF infrastructure.

Accessing the rescue mode can help in restoring a bad grub configuration, getting into a given offile file-system, running fsck or other disk maintenance tasks.

Option 1: interrupting autointall

This option consist on interrupting the standard debian installer autoinstall mechanism (with preseed) and then escaping the install process by means of the debian installer menu, and then operating the underlying operating system.

Option 2: pxe-bootable rescue image

This option is under development. See phab:T78135.

After https://gerrit.wikimedia.org/r/c/operations/puppet/+/654192 it is now possible to use the rescue image during PXE boot. A typical workflow could be:

  1. Powercycle the host.
  2. Force PXE (via F12 for example on Dells).
  3. When the "boot: " prompt pops up, type "rescue" and hit enter.