Document an edge-case with resume and mounting (#4581)

When trying to read keyfiles from an encrypted partition to unlock the swap,
a cyclic dependency is generated because systemd can not mount the
filesystem before it has checked if there is a swap to resume from.

Closes #3940

diff --git a/man/bootup.xml b/man/bootup.xml
index 9869963..b92c60f 100644 (file)
--- a/man/bootup.xml
+++ b/man/bootup.xml
@@ -179,6 +179,13 @@
     identical to the system manager bootup (see above) until it
     reaches <filename>basic.target</filename>. From there, systemd
     approaches the special target <filename>initrd.target</filename>.
+
+    Before any file systems are mounted, it must be determined whether
+    the system will resume from hibernation or proceed with normal boot.
+    This is accomplished by <filename>systemd-hibernate-resume@.service</filename>
+    which must be finished before <filename>local-fs-pre.target</filename>,
+    so no filesystems can be mounted before the check is complete.
+
     When the root device becomes available,
     <filename>initd-root-device.target</filename> is reached.
     If the root device can be mounted at