What is the Emergency Shell (emergency.target) of the Systemd, and in what case is it used?

Question

While reading some info about Systemd, I saw there was an 'emergency' Runlevel, linked to 'emergency.target'. Any idea what it is, and when they use it? Merci

Answer 1

Bonjour. The best write up comes from Red Hat.

The first step in severe problem resolution is rescue mode initiated with:

~]# systemctl rescue

Broadcast message from root@localhost on pts/0 (Fri 2013-10-25 18:23:15 CEST):

The system is going down to rescue mode NOW!

However there are times where rescue mode doesn't work and you have to enter emergency mode. This mounts foot file system as read-only, doesn't mount any other local file systems and doesn't enable network connections. To enter emergency mode use:

systemctl emergency

This is an abbreviated summary so please read the Red Hat link for more detailed systemd usage.

All-in-all I think we all hope we never have to use rescue target in the first place or emergency target second place.