Here are the steps I followed to disable systemd and switch back to init in a debian unstable/i386 system.
Step 1: Comment out all fstab entries for external hds, nfs.
Step 2: Run:
# apt-get update
# apt-get install sysvinit sysvinit-core systemd-shim
Step2 should automatically remove systemd-sysv if not:
# apt-get remove systemd-sysv
For the record, systemd was accidentally installed after a dist-upgrade as a libpam dependency and caused many problems (eg. no kernel modules could be loaded, some fstab entries caused a deadlock etc).
Thanks to #debian-next/@OFTC for the support. :)
+An interesting website: