diff --git a/man/kernel-command-line.xml b/man/kernel-command-line.xml
index e39f108d8f..6e791192b2 100644
--- a/man/kernel-command-line.xml
+++ b/man/kernel-command-line.xml
@@ -137,10 +137,13 @@
enables fully state-less boots were the vendor-supplied OS is used as shipped, with only default
configuration and no stored state in effect, as /etc and /var (as
well as all other resources shipped in the root file system) are reset at boot and lost on shutdown. If this
- setting is set to state the root file system is mounted as usual, however
+ setting is set to state the root file system is mounted read-only, however
/var is mounted as a volatile memory file system (tmpfs), so that the
- system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. For details,
- see
+ system boots up with the normal configuration applied, but all state reset at boot and lost at shutdown. If
+ this setting is set to overlay the root file system is set up as
+ overlayfs mount combining the read-only root directory with a writable
+ tmpfs, so that no modifications are made to disk, but the file system may be modified
+ nonetheless with all changes being lost at reboot. For details, see
systemd-volatile-root.service8
and
systemd-fstab-generator8.
diff --git a/man/systemd-fstab-generator.xml b/man/systemd-fstab-generator.xml
index ab706420c5..7897ce50e9 100644
--- a/man/systemd-fstab-generator.xml
+++ b/man/systemd-fstab-generator.xml
@@ -175,19 +175,25 @@
lost at shutdown, as /etc and /var will be served from the (initially
unpopulated) volatile memory file system.
- If set to the generator will leave the root
- directory mount point unaltered, however will mount a tmpfs file system to
- /var. In this mode the normal system configuration (i.e. the contents of
- /etc) is in effect (and may be modified during system runtime), however the system state
- (i.e. the contents of /var) is reset at boot and lost at shutdown.
+ If set to the generator will leave the root directory mount point unaltered,
+ however will mount a tmpfs file system to /var. In this mode the normal
+ system configuration (i.e. the contents of /etc) is in effect (and may be modified during
+ system runtime), however the system state (i.e. the contents of /var) is reset at boot and
+ lost at shutdown.
+
+ If this setting is set to overlay the root file system is set up as
+ overlayfs mount combining the read-only root directory with a writable
+ tmpfs, so that no modifications are made to disk, but the file system may be modified
+ nonetheless with all changes being lost at reboot.Note that in none of these modes the root directory, /etc, /var
or any other resources stored in the root file system are physically removed. It's thus safe to boot a system
that is normally operated in non-volatile mode temporarily into volatile mode, without losing data.
- Note that enabling this setting will only work correctly on operating systems that can boot up with only
- /usr mounted, and are able to automatically populate /etc, and also
- /var in case of systemd.volatile=yes.
+ Note that with the exception of overlay mode, enabling this setting will only work
+ correctly on operating systems that can boot up with only /usr mounted, and are able to
+ automatically populate /etc, and also /var in case of
+ systemd.volatile=yes.