SlackBuildsOrg/system/early-ssh

early-ssh is a simple initramfs hook, which installs Dropbear SSH server
into your initramfs, and starts it at boottime, so you will be able to
do a lot of things remotely over SSH, before your root partition gets
mounted, for example:

* unlocking LUKS encrypted crypto devices - even your root can be an
  encrypted filesystem
* assembling/altering RAID arrays (mdadm)
* checking the root filesystem in read-write mode, taking action in case
  of errors
* and so on...