Systemd: how to get into rescue mode

[Liam Proven]

On Mon, 6 Jan 2020 at 13:30, Volker Wysk <post at volker-wysk.de> wrote:
>
> Again, from that magazine article, I'd expect the rescue.target to
> work, and spawn a shell. And this should be in single-user mode (as far
> as I can tell), although it isn't mentioned.

Yes, I would too. So I do not know why it isn't working. That is what
I was trying to say.

> From what I've read on the web, there is the systemd target "multi-
> user.target", which should do what you have in mind. But I really don't
> know much about systemd.

AFAIK, it must be explicitly configured by the distro vendor, and
again AFAIK, most do not.

> I've been exposed to systemd only a little so far, but I like it.

I did when I first got it: my computer booted substantially quicker.

Then I discovered that the result of dual-booting with Win10 and
automatically mounting my Windows partition when in Linux was that
systemd prevented my machine from booting.

This is a known issue, due to choices by Microsoft, and I've now fixed
it, but it took considerable troubleshooting at the time.

> I
> also like Gnome 3.

Chacun à son goût.

> > [2] Familiarize yourself with booting the kernel and initrd from
> > removable media, but mounting and running root from the hard disk.
> > This is a real life-saver sometimes.
>
> What would be the benefit? It sounds complicated to set up.

It is not difficult at all. It is merely a matter of editing the boot
line in GRUB on your live media.

What it means is that if your system is so screwed up that it won't
boot, you can still boot it from external media but get at *your*
installation.

For instance, while experimenting with different methods to
automatically remove old kernels after updating, I once accidentally
removed _all_ kernels. Leaving me a complete, intact OS that could not
boot.

If you know how to start the PC from USB but load your installed
copy's root filesystem, this is trivial to fix: boot, apt-install the
current kernel, let it update GRUB and it's fixed.

If you can't do that, it's very hard to fix and probably means a reinstall.


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