mdadm: load default sysfs attributes after assemblation

[thirdparty/mdadm.git] / mdmon.8

diff --git a/mdmon.8 b/mdmon.8
index df9dfbcee7c0a172fd1b842d0414789230c80923..4cbc2ba7ef5f5b40faef77eeb0051d883ef61c4c 100644 (file)
--- a/mdmon.8
+++ b/mdmon.8
@@ -1,11 +1,11 @@
 .\" See file COPYING in distribution for details.
-.TH MDMON 8 "" v3.1.1
+.TH MDMON 8 "" v4.1-rc2
 .SH NAME
 mdmon \- monitor MD external metadata arrays
 
 .SH SYNOPSIS
 
-.BI mdmon " [--all] [--takeover] CONTAINER"
+.BI mdmon " [--all] [--takeover] [--foreground] CONTAINER"
 
 .SH OVERVIEW
 The 2.6.27 kernel brings the ability to support external metadata arrays.
@@ -101,10 +101,10 @@ call is still required.
 External metadata formats, like DDF, differ from the native MD metadata
 formats in that they define a set of disks and a series of sub-arrays
 within those disks.  MD metadata in comparison defines a 1:1
-relationship between a set of block devices and a raid array.  For
-example to create 2 arrays at different raid levels on a single
+relationship between a set of block devices and a RAID array.  For
+example to create 2 arrays at different RAID levels on a single
 set of disks, MD metadata requires the disks be partitioned and then
-each array can created be created with a subset of those partitions.  The
+each array can be created with a subset of those partitions.  The
 supported external formats perform this disk carving internally.
 .P
 Container devices simply hold references to all member disks and allow
@@ -131,6 +131,14 @@ The
 device to monitor.  It can be a full path like /dev/md/container, or a
 simple md device name like md127.
 .TP
+.B \-\-foreground
+Normally,
+.I mdmon
+will fork and continue in the background.  Adding this option will
+skip that step and run
+.I mdmon
+in the foreground.
+.TP
 .B \-\-takeover
 This instructs
 .I mdmon
@@ -157,6 +165,15 @@ This tells mdmon to find any active containers and start monitoring
 each of them if appropriate.  This is normally used with
 .B \-\-takeover
 late in the boot sequence.
+A separate
+.I mdmon
+process is started for each container as the
+.B \-\-all
+argument is over-written with the name of the container.  To allow for
+containers with names longer than 5 characters, this argument can be
+arbitrarily extended, e.g. to
+.BR \-\-all-active-arrays .
+.TP
 
 .PP
 Note that
@@ -164,7 +181,7 @@ Note that
 is automatically started by
 .I mdadm
 when needed and so does not need to be considered when working with
-RAID arrays.  The only times it is run other that by
+RAID arrays.  The only times it is run other than by
 .I  mdadm
 is when the boot scripts need to restart it after mounting the new
 root filesystem.
@@ -178,6 +195,11 @@ mounted there are special considerations when the root filesystem is
 mounted from an
 .I mdmon
 monitored device.
+Note that in general
+.I mdmon
+is needed even if the filesystem is mounted read-only as some
+filesystems can still write to the device in those circumstances, for
+example to replay a journal after an unclean shutdown.
 
 When the array is assembled by the
 .B initramfs
@@ -187,23 +209,20 @@ as required.  This means that
 .I mdmon
 must be installed on the
 .B initramfs
-and there must be a writable filesystem (typically tmpfs) which
+and there must be a writable filesystem (typically tmpfs) in which
 .B mdmon
 can create a
 .B .pid
 and
 .B .sock
-file on.  The particular filesystem to use is given to mdmon at compile
+file.  The particular filesystem to use is given to mdmon at compile
 time and defaults to
-.BR /lib/init/rw .
+.BR /run/mdadm .
 
-This filesystem must persist through to the end of the boot sequence.
+This filesystem must persist through to shutdown time.
 
 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"
@@ -211,31 +230,28 @@ so that the
 .I mdmon
 running from the
 .B initramfs
-can be replaced with one running in the main root.
+can be replaced with one running in the main root, and so the
+memory used by the initramfs can be released.
 
 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.
-
-
+.B /dev
+(by default) it will not be possible to unmount
+.B /dev
+if it is a separate filesystem.
 
 .SH EXAMPLES
 
-.B "  mdmon \-\-all \-\-takeover"
+.B "  mdmon \-\-all-active-arrays \-\-takeover"
 .br
 Any
 .I mdmon
 which is currently running is killed and a new instance is started.
-This should be run late in the boot sequence and particularly after
-.B /var
-is mounted and writable.
+This should be run during in the boot sequence if an initramfs was
+used, so that any mdmon running from the initramfs will not hold
+the initramfs active.
 .SH SEE ALSO
 .IR mdadm (8),
 .IR md (4).