From cd9a8b5cb4c2a402dbc2bf0ce314cd87285bcf4d Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 8 Feb 2010 14:43:51 +1100 Subject: mdmon: Document startup/shutdown requirements in man page. Signed-off-by: NeilBrown --- mdmon.8 | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 58 insertions(+), 1 deletion(-) diff --git a/mdmon.8 b/mdmon.8 index 2720b45..df9dfbc 100644 --- a/mdmon.8 +++ b/mdmon.8 @@ -21,7 +21,7 @@ To service metadata update requests a daemon, is introduced. .I Mdmon is tasked with polling the sysfs namespace looking for changes in -.BR array_state , +.BR array_state , .BR sync_action , and per disk .BR state @@ -169,6 +169,63 @@ RAID arrays. The only times it is run other that by is when the boot scripts need to restart it after mounting the new root filesystem. +.SH START UP AND SHUTDOWN + +As +.I mdmon +needs to be running whenever any filesystem on the monitored device is +mounted there are special considerations when the root filesystem is +mounted from an +.I mdmon +monitored device. + +When the array is assembled by the +.B initramfs +code, mdadm will automatically start +.I mdmon +as required. This means that +.I mdmon +must be installed on the +.B initramfs +and there must be a writable filesystem (typically tmpfs) which +.B mdmon +can create a +.B .pid +and +.B .sock +file on. The particular filesystem to use is given to mdmon at compile +time and defaults to +.BR /lib/init/rw . + +This filesystem must persist through to the end of the boot sequence. + +After the final root filesystem has be instantiated (usually with +.BR pivot_root ) +and after +.B /var +is mounted writable, +.I mdmon +should be run with +.I "\-\-all \-\-takeover" +so that the +.I mdmon +running from the +.B initramfs +can be replaced with one running in the main root. + +At shutdown time, +.I mdmon +should not be killed along with other processes. Also as it holds a +file (socket actually) open in +.B /var +it will not be possible to unmount +.B /var +if it is a separate filesystem. Rather the +.B /var +filesystem, like the root filesystem, should be remounted read-only. + + + .SH EXAMPLES .B " mdmon \-\-all \-\-takeover" -- cgit v1.2.1