Introduction
># systemctl list-units --type target --all
UNIT
emergency.target
rescue.target
...
# systemctl get-default
multi-user.target
Boot in emergency.target
When the boot-loader menu appears, press any key to interrupt the countdown, except Enter.
Use the cursor keys to highlight the default boot-loader entry.
Press e to edit the current entry.
Use the cursor keys to navigate the line that starts with linux text.
Press Ctrl+e to move the cursor to the end of the line.
Append the systemd.unit=emergency.target text to the end of the line.
Press Ctrl+x to boot using the modified configuration.
># mount -o remount,rw /
# mount -a
# vim /etc/fstab
# systemctl daemon-reload
# mount -a
# systemctl reboot