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We have a RHEL8 machine in a different city that needs to be rescued. The machine is connected to a serial console, and we can successfully access the BIOS and choose a disk to boot from.

Our problem starts when we choose our existing USB rescue disk - nothing happens on the serial console, we lose serial access.

We need a Linux rescue disk that "just works" out the box with a serial cable. Does such a rescue disk exist?

There are a lot of hits for instructions on how to modify grub after booting, but these presuppose a suitably qualified person at the keyboard, and we do not have that. This is why this question relates to rescue with built in serial support, not serial support that is added in afterwards at the physical keyboard of the machine.

Graham Leggett
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  • Who will be writing the rescue disk to USB – you or the remote person at the keyboard? – u1686_grawity Sep 23 '22 at 11:29
  • I'm surprised it is no more possible (but I didn't use serial console anymore) Possibly any rescue disk before `systemd`. I think on sysvinit it was standard to open console and serial console. – Giacomo Catenazzi Sep 23 '22 at 12:59
  • @user1686 Neither. USB will be written by a remote person at a fully functional different machine running an OS that fits their skillset. – Graham Leggett Sep 23 '22 at 13:31
  • But you can at least provide them with a pre-made image, instead of asking them to download a stock Foobar Linux ISO? – u1686_grawity Sep 23 '22 at 15:23
  • Embedded systems that rely on a serial console typically have the convenience of a designated UART in the SOC for the console or DEBUG port. Since the console is hardwired, the configuration is fixed and the boot programs can be hardcoded to always use this designated port . But on a (modern) PC, serial ports are no longer standard. PC programs will have to be more complicated, and allow HW configuration. Or require a specific HW configuration. – sawdust Sep 23 '22 at 21:04
  • "*Does such a rescue disk exist?*" -- Yes, if you're willing/able to make it yourself. The serial port drivers would have to be built as part of the kernel image, rather than built as loadable modules. The default kernel command line would specify the port as the console. The system init would have to run a getty on that serial terminal for a login. – sawdust Sep 23 '22 at 21:10
  • Eventually worked around issue by using pxelinux to provide a kernel/initrd combo with console over serial. Given serial consoles are standard in hypervisors, and now standard in AWS and Azure instances, it's strange that they don't work out the box. – Graham Leggett Sep 25 '22 at 09:18

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