[systemd-devel] emergency, rescue and single-user

Jan Synacek jsynacek at redhat.com
Tue Dec 9 22:45:55 PST 2014

Lennart Poettering <lennart at poettering.net> writes:
> On Tue, 09.12.14 13:43, Jan Synáček (jsynacek at redhat.com) wrote:
>> Hello,
>> what is the difference between emergency, rescue and single-user?
>> On F21, systemd-216-12.fc21.x86_64, they all boot into something that
>> presents itself as "Welcome to emergency mode!" and they all require a
>> root password. In case of booting into emergency.target, I can see
>> "Starting Emergency Shell" in the console output. In single-user and
>> rescue.target, I can see "Starting Rescue Shell", but they all look the
>> same. systemd.special(7) doesn't help much.
> "rescue" is simply how we call the old sysv "single user" mode. This
> means all early-boot services are started, but no later boot
> service. File systems are hence checked, udev is started, and so
> on. You get your shell right after sysinit.target but before
> basic.target basically.
> "emergency" maps to the "emergency" mode that sysvinit already knew:
> it just starts a shell, and does nothing else. No early-boot services
> are run. No udev, no file system checks, no nothing.
> Lennart

Thanks for the explanation!

Jan Synacek
Software Engineer, Red Hat
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