Systemd: how to get into rescue mode

[Little Girl]

Hey there,

Tom H wrote:
>On Sat, Jan 11, 2020 at 1:52 AM Little Girl wrote:

>> That command will work from an ordinary terminal (although I prefer
>> the Alt + Shift + SysRq REISUO method so that everything is nice
>> and neat and there are no loose ends).  

>In a default install, REISUB and REISUO will fail because, for
>example, E and I aren't allowed.

Interesting. They work for me right now in Ubuntu MATE and have been
working for years. By that, I mean that they effectively shut down or
reboot my system when I use them; I just tried them again to verify.
Have you tried them?

Also, where did you get that information? Do you have a link for
further information on that? The E and the I are vital for
safeguarding data. Without them, you may as well use any other
shutdown or reboot method.

Perhaps I'm not understanding you correctly. What, exactly, do you
mean by a default install? I've never done the commands on an
installation of an Ubuntu flavor without having done something to
customize it. I have a whole bunch of things I do to my Ubuntu MATE
or Kubuntu installations to "make them mine"  (tweaks and
installations and start-up scripts) and any or all of them might
qualify my set-up as non-default.

>"systemctl poweroff" and all of its systemd-sysv equivalents are just
>as "nice and neat" and have "no loose ends."

I'll take your word for it since I haven't checked. I just know that
REISUB and REISUO are presented as safe methods for rebooting or
shutting down while making sure nothing is left unsaved, which is
vital. I'm also pretty sure (but not positive) that shutdown -r now
doesn't offer the same protection. I just checked the shutdown man
page and didn't see a mention of that.

>> The ones above, however, are for use from within a Systemd
>> target.  
>
>All of these commands are for use within any runlevel / systemd
>target.

I wasn't aware that you could use the shutdown -r now command from
within Systemd. The extent of my knowledge on the topic has consisted
of several ventures onto various sites in the past couple of days out
of curiosity on how to "git 'er done" in Systemd since it seems that
I'll be wanting to have that in my arsenal as well. You never know
when you might need something like that. All the examples I've found
so far have given either Systemd commands or telinit commands, so I
figured that was all you could do. It's nice to know that more can be
done and I'll look into it further by and by. Thanks for chiming in.

-- 
Little Girl

There is no spoon.