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Weird

Not really, I pulled it together from a bunch of random posts lol

Maybe I should write one, but in essence you:

• Stop all non-OS essential services

• Create a filesystem in a chunk of RAM

• Pull essential OS files from the installed OS into it recreating needed directories (Though you could probably just use a tiny pre-built distro but meh)

• Pivot root into it

• Reload services (when they restart they’ll be restarted in the context of where you pivot rooted, prior they’re still running under the context of the installed OS)

• Unmount the boot drive

• Then do what ever you need to do

• ???

• Profit

Yeah, I’d love to see a write up on this to follow.Sounds like useful practice in the lab if nothing else.

Well the 1 SSH session bit was for dramatic meme-effect lol, you can actually connect back without issue (at least it did for me) so worst case if you weren’t working in tmux you’d just have to start dd again

Worst worst case, you’d just end up back where you were probably heading before anyways, KVM/IPMI

You could use screen or tmux for a persistent terminal session.

As long as you only copy off the disk, you can just reboot and the whole system in RAM vanishes and the normal system boots again for the second try.

Maybe run ssh on 2 different ports?

I had a server I rented from a provider in a data center and I wanted to image (dd) the drive for archival before I decommissioned it from my infrastructure.

Normally, you can’t really do that with the OS running and you would have to shut down and insert a live USB or something and temporarily boot from that. The server being a faraway rental the only option was to open a ticket so that they could enable an out-of-band management option like KVM or IPMI. Which would allow you to control a machine as if you had a physical monitor, keyboard and mouse in front of you. With that you can attach flash drives, shutdown, restart, see the POST/BIOS/UEFI screens etc remotely .

But, I didn’t want to wait 6-8 hours for them to enable that so instead I put together a process that would “boot” me into another distro “installed” into a RAM disk (kinda like how live CD/USB works) from the currently installed and running OS without rebooting

From there I could unmount the boot disk and do what ever I wanted from there, I could have even wiped the disk entirely and installed a entirely different distro if I wanted

RAM is still memory, so you can put anything in there, like an OS.

With pivot_root, you can change where the root is. So you pivot into your OS in RAM, which becomes the root of the system.

At that point, you can do pretty much anything you would normally do with your OS, like unmount a HDD.

I’ve never personally done it, but that’s a simplified explanation of what OP did.

Really? It seemed to go pretty smooth for me, SSH dropped once I think when I reloaded the services (expected), but after that I was able to connect back fine on the same port no issue

If that happens, they just fall back to the first option of waiting for their provider to set up the IPMI.

Damn lol wish I would have come out sooner lmao Seems a tad more complicated though, I don’t remember having to compile anything at least

Heh, this expertise is built on hundreds of “Why tf won’t X boot from Y!!” and solid research skills lol you’ll get there

Not sure about your hardware, but try to look up if it requires a special kernel, like the RPi 5 (which only runs on raspbian because they ship that kernel)