From: Lennart Poettering Date: Fri, 21 Dec 2018 23:51:13 +0000 (+0100) Subject: man: document new systemd.volatile=overlay kernel command line option X-Git-Tag: v242-rc1~217^2 X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=13070a70ef8c8a790024698a3b84cb7323a0d0ca;p=thirdparty%2Fsystemd.git man: document new systemd.volatile=overlay kernel command line option --- diff --git a/man/kernel-command-line.xml b/man/kernel-command-line.xml index e39f108d8f4..6e791192b2b 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 ab706420c5d..7897ce50e94 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.