Add --offroot argument to mdadm

When --offroot is specified, mdadm will change the first character of
argv[0] to '@'. This is used to signal to systemd that mdadm was
launched from initramfs and should not be shut down before returning
to the initramfs.

Acked-by: Doug Ledford <dledford@redhat.com>
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.de>

ReadMe.c

@@ -111,6 +111,7 @@ struct option long_options[] = {
     {"kill-subarray", 1, 0, KillSubarray},
     {"update-subarray", 1, 0, UpdateSubarray},
     {"udev-rules", 2, 0, UdevRules},
+    {"offroot", 0, 0, OffRootOpt},
 
     /* synonyms */
     {"monitor",   0, 0, 'F'},
@@ -268,6 +269,10 @@ char OptionHelp[] =
 "  --query       -Q   : Display general information about how a\n"
 "                       device relates to the md driver\n"
 "  --auto-detect      : Start arrays auto-detected by the kernel\n"
+"  --offroot          : Set first character of argv[0] to @ to indicate the\n"
+"                       application was launched from initrd/initramfs and\n"
+"                       should not be shutdown by systemd as part of the\n"
+"                       regular shutdown process.\n"
 ;
 /*
 "\n"

mdadm.8.in

@@ -254,6 +254,18 @@ Avoid printing purely informative messages.  With this,
 .I mdadm
 will be silent unless there is something really important to report.
 
+.TP
+.BR \-\-offroot
+Set first character of argv[0] to @ to indicate mdadm was launched
+from initrd/initramfs and should not be shutdown by systemd as part of
+the regular shutdown process. This option is normally only used by
+the system's initscripts. Please see here for more details on how
+systemd handled argv[0]:
+.IP
+.B http://www.freedesktop.org/wiki/Software/systemd/RootStorageDaemons
+.PP
+
+
 .TP
 .BR \-f ", " \-\-force
 Be more forceful about certain operations.  See the various modes for

mdadm.c

@@ -174,6 +174,15 @@ int main(int argc, char *argv[])
 				homehost = optarg;
 			continue;
 
+		/*
+		 * --offroot sets first char of argv[0] to @. This is used
+		 * by systemd to signal that the tast was launched from
+		 * initrd/initramfs and should be preserved during shutdown
+		 */
+		case OffRootOpt:
+			argv[0][0] = '@';
+			continue;
+
 		case ':':
 		case '?':
 			fputs(Usage, stderr);

mdadm.h

@@ -321,6 +321,7 @@ enum special_options {
 	UdevRules,
 	FreezeReshape,
 	Continue,
+	OffRootOpt,
 };
 
 /* structures read from config file */