Ubuntu
casper package

live-media=<device> is no more supported in casper

Bug #653633 reported by phl on 2010-10-02

This bug affects 4 people

Affects		Status	Importance	Assigned to	Milestone
	casper (Ubuntu)	Won't Fix	Undecided	Unassigned

Bug Description

Binary package hint: casper

From Changelog:

casper (1.77+debian-1) unstable; urgency=low
+
+ ......
+ * Added boot parameter "live-media=<device>" to force trying to boot from
+ a specified device.

From man casper (casper_1.246_i386.deb)

{live-media|bootfrom}=DEVICE
If you specify one of this two equivalent forms, casper will first try to find this device for the "/casper" directory where the read-only root filesystem should reside. If it did not find something usable, the normal scan for block devices is performed.

But from some time ago, this feature has disappeared.

In /usr/share/initramfs-tools/scripts/casper, in the function

parse_cmdline ()
{
    PRESEEDS=
    # looking for casper specifics options as kernel parameters
    for x in $(cat /proc/cmdline); do
        case $x in

these two lines are no more here

bootfrom=*|live-media=*)
export LIVEMEDIA=${x#*=} ;;

But it seems that support for this feature still exists partially:

find_livefs() {
    timeout="${1}"
    # first look at the one specified in the command line
    if [ ! -z "${LIVEMEDIA}" ]; then
        if check_dev "null" "${LIVEMEDIA}" "skip_uuid_check"; then
            return 0
        fi
    fi
    # don't start autodetection before timeout has expired
    if [ -n "${LIVEMEDIA_TIMEOUT}" ]; then

Actually, more often, this interesting feature never worked well because the misplaced timeout make the only one try to use ${LIVEMEDIA} too early, before USB are ready, so few people noticed its disappearance.

I suggest restoring parse_cmdline () and moving check_dev "null" "${LIVEMEDIA}" after time-out

Ph.L.

Revision history for this message

tarski (guy-laffitte) wrote on 2010-11-26:

I have a couple of remarks to formulate about this bug.

1. I have been unable to find where variable LIVEMEDIA_TIMEOUT is set. If is is never set, it is useless. There are thus two solutions : either remove it, or add boot parameter ( for example "live-media-timeout=xx" ) to set it.

2. A user who specifies "live_media" boot parameter ( generally ) does not want to boot on another device. The use of this parameter did not work well because the script fell back in normal scan when the attempt with LIVEMEDIA failed. The race condition is generally not in favour of USB devices faced to other ones, due to latency.
I prefer not to waste time in case of boot failure if there is a mistake in live-media parameter rather than a successful boot on a wrong device. So, I propose to make scan of LIVEMEDIA and normal scan mutually exclusive. In "find_livefs" the code could be something like this ( letting drop LIVEMEDIA_TIMEOUT ) :

  if [ ! -z "${LIVEMEDIA}" ]; then
    # scan with LIVEMEDIA
  else
    # normal scan
  fi

Revision history for this message

Brian Murray (brian-murray) wrote on 2011-10-21:

The code for this is significantly different in Oneiric and it seems that it is supported now just with a different name.

            live-media-path=*)
                LIVE_MEDIA_PATH="${x#live-media-path=}"
                export LIVE_MEDIA_PATH
                echo "export LIVE_MEDIA_PATH=\"$LIVE_MEDIA_PATH\"" >> /etc/casper.conf ;;

As such I'm setting this to Won't Fix.

Changed in casper (Ubuntu):
status:	New → Won't Fix

Revision history for this message

phl (ubuntu-leledy) wrote on 2011-10-23:

I think you arre speaking about uuid= , don't you ?
Could you remove reference to live-media-path in man casper. It's a lot of waste time trying this feature which will never work ?
Thanks.

By the way, because of this bug I had to use my own method, more general that the new uuid= because any udev property may be selected, and I rely only on udev for discovering live-media. Casper just waits udev discover the right disk.

Ph.L

Revision history for this message

phl (ubuntu-leledy) wrote on 2011-10-24:

Download full text (6.7 KiB)

Here is my udev based live-device recognition system. Diff from 10.10 release

--1----------------------------------------------------------------------------------------------------
EXTLINUX config :
kernel ../casper/vmlinuz1
append initrd=../casper/initramfs-USB-UDEV boot=casper livecasper-dev=udev=UUID=fc0e5af3-e635-4ef9-831d-0ea4f4e70a60 livehome-dev=udev=UUID=695d19b0-78d9-4dc3-ab3f-6f0cf2f315b4
------------------
/etc/udev/rules.d/61-casper-usb.rules:
# Used to make casper event driven instead of repeatedly scan all block devices
# With this rule finding live-media device is mainly udev's job

# Does not work when named 60-xxx.rules but does work whan named 61-xxx.rules

ENV{ID_USB_DRIVER}!="usb-storage", GOTO="end_usb-casper.rules"
ACTION!="add|change", GOTO="end_usb-casper.rules"

--2---------------------------------------------------------------------------------------------------
--- casper_1.248_i386.deb.d/usr/share/initramfs-tools/scripts/casper 2010-09-16 01:34:18.000000000 +0200
+++ ~/usr/share/initramfs-tools/scripts/casper 2010-11-11 18:52:50.000000000 +0100
@@ -1,5 +1,10 @@
#!/bin/sh

+# make udev does most of the search
+# -1- livecasper-dev=udev=UUID
+# a) ln -s xxx /dev/.livecasper
+# b) ln -s yyy /dev/.livehome
+# -2- suppress snapshots
# set -e

export PATH=/usr/bin:/usr/sbin:/bin:/sbin
@@ -31,7 +36,7 @@

parse_cmdline() {
     for x in $(cat /proc/cmdline); do
- case $x in
+ case $x in
             showmounts|show-cow)
                 export SHOWMOUNTS='Yes' ;;
             persistent)
@@ -50,6 +55,28 @@
                 export STATICIP ;;
             ignore_uuid)
                 IGNORE_UUID="Yes" ;;
+ livecasper-dev=*)
+ LIVE_CASPER_DEV="${x#livecasper-dev=}"
+ export LIVE_CASPER_DEV
+ echo "export LIVE_CASPER_DEV=\"$LIVE_CASPER_DEV\"" >> /etc/casper.conf
+ case ${LIVE_CASPER_DEV} in
+ udev=UUID=*)
+ LIVE_CASPER_UDEV_UUID="${LIVE_CASPER_DEV#udev=UUID=}"
+ export LIVE_CASPER_UDEV_UUID
+ echo "export LIVE_CASPER_UDEV_UUID=\"$LIVE_CASPER_UDEV_UUID\"" >> /etc/casper.conf ;;
+ esac
+ ;;
+ livehome-dev=*)
+ LIVE_HOME_DEV="${x#livehome-dev=}"
+ export LIVE_HOME_DEV
+ echo "export LIVE_HOME_DEV=\"$LIVE_HOME_DEV\"" >> /etc/casper.conf
+ case ${LIVE_HOME_DEV} in
+ udev=UUID=*)
+ LIVE_HOME_UDEV_UUID="${LIVE_HOME_DEV#udev=UUID=}"
+ export LIVE_HOME_UDEV_UUID
+ echo "export LIVE_HOME_UDEV_UUID=\"$LIVE_HOME_UDEV_UUID\"" >> /etc/casper.conf ;;
+ esac
+ ;;
             live-media-path=*)
                 LIVE_MEDIA_PATH...

Here is my udev based live-device recognition system.  Diff from 10.10 release

--1----------------------------------------------------------------------------------------------------
EXTLINUX config : 
kernel ../casper/vmlinuz1
	append initrd=../casper/initramfs-USB-UDEV boot=casper livecasper-dev=udev=UUID=fc0e5af3-e635-4ef9-831d-0ea4f4e70a60 livehome-dev=udev=UUID=695d19b0-78d9-4dc3-ab3f-6f0cf2f315b4
------------------
/etc/udev/rules.d/61-casper-usb.rules:
# Used to make casper event driven instead of repeatedly scan all block devices
# With this rule finding live-media device is mainly udev's job
 
# Does not work when named 60-xxx.rules but does work whan named 61-xxx.rules

ENV{ID_USB_DRIVER}!="usb-storage", GOTO="end_usb-casper.rules"
ACTION!="add|change", GOTO="end_usb-casper.rules"

IMPORT{cmdline}="livecasper-dev=udev=UUID"
ENV{ID_FS_UUID}!="",\ 
  PROGRAM=="/bin/sh -c 'test $env{livecasper-dev=udev=UUID}=$env{ID_FS_UUID}'",SYMLINK+=".livecasper"
IMPORT{cmdline}="livehome-dev=udev=UUID"
ENV{ID_FS_UUID}!="", \
  PROGRAM=="/bin/sh -c 'test $env{livehome-dev=udev=UUID} = $env{ID_FS_UUID}'",SYMLINK+=".livehome"
 
--2---------------------------------------------------------------------------------------------------
--- casper_1.248_i386.deb.d/usr/share/initramfs-tools/scripts/casper	2010-09-16 01:34:18.000000000 +0200
+++ ~/usr/share/initramfs-tools/scripts/casper	2010-11-11 18:52:50.000000000 +0100
@@ -1,5 +1,10 @@
 #!/bin/sh
 
+# make udev does most of the search
+# -1- livecasper-dev=udev=UUID
+#     a) ln -s xxx /dev/.livecasper
+#      b) ln -s yyy /dev/.livehome
+# -2- suppress snapshots
 # set -e
 
 export PATH=/usr/bin:/usr/sbin:/bin:/sbin
@@ -31,7 +36,7 @@
 
 parse_cmdline() {
     for x in $(cat /proc/cmdline); do
-        case $x in
+        case $x in           
             showmounts|show-cow)
                 export SHOWMOUNTS='Yes' ;;
             persistent)
@@ -50,6 +55,28 @@
                 export STATICIP ;;
             ignore_uuid)
                 IGNORE_UUID="Yes" ;;
+            livecasper-dev=*)
+                LIVE_CASPER_DEV="${x#livecasper-dev=}"
+                export LIVE_CASPER_DEV
+                echo "export LIVE_CASPER_DEV=\"$LIVE_CASPER_DEV\"" >> /etc/casper.conf 
+                case ${LIVE_CASPER_DEV} in
+                  udev=UUID=*)
+                  LIVE_CASPER_UDEV_UUID="${LIVE_CASPER_DEV#udev=UUID=}"
+                  export LIVE_CASPER_UDEV_UUID
+                  echo "export LIVE_CASPER_UDEV_UUID=\"$LIVE_CASPER_UDEV_UUID\"" >> /etc/casper.conf ;;
+                  esac 
+                ;;
+            livehome-dev=*)
+                LIVE_HOME_DEV="${x#livehome-dev=}"
+                export LIVE_HOME_DEV
+                echo "export LIVE_HOME_DEV=\"$LIVE_HOME_DEV\"" >> /etc/casper.conf 
+                case ${LIVE_HOME_DEV} in
+                  udev=UUID=*)
+                  LIVE_HOME_UDEV_UUID="${LIVE_HOME_DEV#udev=UUID=}"
+                  export LIVE_HOME_UDEV_UUID
+                  echo "export LIVE_HOME_UDEV_UUID=\"$LIVE_HOME_UDEV_UUID\"" >> /etc/casper.conf ;;
+                  esac 
+                ;;
             live-media-path=*)
                 LIVE_MEDIA_PATH="${x#live-media-path=}"
                 export LIVE_MEDIA_PATH
@@ -295,7 +322,7 @@
 }
 
 try_snap ()
-{
+{   return 1
     # Look for $snap_label.* in block devices and copy the contents to $snap_mount
     #   and remember the device and filename for resync on exit in casper.init
 
@@ -463,7 +490,7 @@
     if [ -n "${SHOWMOUNTS}" ]; then
         for d in ${rofslist}; do
             mkdir -p "${rootmnt}/${LIVE_MEDIA_PATH}/${d##*/}"
-            case d in
+            case $d in
                 *.dir) # do nothing # mount -o bind "${d}" "${rootmnt}/${LIVE_MEDIA_PATH}/${d##*/}"
                     ;;
                 *)
@@ -541,6 +568,12 @@
 find_livefs() {
     timeout="${1}"
     # first look at the one specified in the command line
+    if [ ! -z "${LIVE_CASPER_UDEV_UUID}" ] ; then
+      livecasper_FROM_UDEV=$( readLinkWait .livecasper )
+        if check_dev "null" /dev/"${livecasper_FROM_UDEV}" "skip_uuid_check"; then
+            return 0
+        fi
+    fi         
     if [ ! -z "${LIVEMEDIA}" ]; then
         if check_dev "null" "${LIVEMEDIA}" "skip_uuid_check"; then
             return 0
--3----------------------------------------------------------------------------------------------------------------------
--- casper_1.248_i386.deb.d/usr/share/initramfs-tools/scripts/casper-helpers	2010-09-16 01:34:18.000000000 +0200
+++ ~/usr/share/initramfs-tools/scripts/casper-helpers	2010-11-11 20:46:32.000000000 +0100
@@ -1,5 +1,22 @@
 ## Casper helper functions, used by casper on boot and by casper-snapshot
 
+# readLinkWait
+# suppress ntfs 
+
+# first, a short wait, just in case link is made by udev after first readlink but before first inotifywait 
+
+readLinkWait() {
+	local link=/dev/$1
+	readlink $link || { 
+		touch $link 
+		inotifywait -qq -e ATTRIB --timeout 1 $link 
+		readlink $link 
+	} || {
+        inotifywait -qq -e ATTRIB --timeout 10 $link 
+        readlink $link
+        } 
+}
+
 if [ "${BUILD_SYSTEM}" = "Debian" ] || [ "${BUILD_SYSTEM}" = "Ubuntu" ]; then
     MP_QUIET="-q"
 else
@@ -182,6 +199,14 @@
 
 find_cow_device() {
     pers_label="${1}"
+    [ ${pers_label} = casper-rw ] && return 1
+
+    if [ ! -z "${LIVE_HOME_UDEV_UUID}" ] ; then
+      livehome_FROM_UDEV=$(readLinkWait .livehome) 		
+      echo  /dev/"${livehome_FROM_UDEV}"
+      return
+    fi
+
     cow_backing="/${pers_label}-backing"
 
     if [ -z "${PERSISTENT_PATH}" ]; then
@@ -190,7 +215,7 @@
         pers_fpath=${cow_backing}/${PERSISTENT_PATH}/${pers_label}
     fi
 
-    for sysblock in $(echo /sys/block/* | tr ' ' '\n' | grep -v loop); do
+    for sysblock in $(echo /sys/block/* | tr ' ' '\n' | egrep -v '/(loop|ram|sr|fd)'); do
         for dev in $(subdevices "${sysblock}"); do
             devname=$(sys2dev "${dev}")
             if [ "$(/sbin/blkid -s LABEL -o value $devname 2>/dev/null)" = "${pers_label}" ]; then
---4 ---------------------------------------------------------------------------------------------------
--- casper_1.248_i386.deb.d/usr/share/initramfs-tools/hooks/casper	2010-09-16 01:34:18.000000000 +0200
+++ ~/usr/share/initramfs-tools/hooks/casper	2010-10-15 17:16:04.000000000 +0200
@@ -72,8 +74,8 @@
 # integrity check
 copy_exec /usr/lib/casper/casper-md5check /bin
 
-cp /usr/share/initramfs-tools/scripts/casper-functions $DESTDIR/scripts
-cp /usr/share/initramfs-tools/scripts/casper-helpers $DESTDIR/scripts
+#cp /usr/share/initramfs-tools/scripts/casper-functions $DESTDIR/scripts
+#cp /usr/share/initramfs-tools/scripts/casper-helpers $DESTDIR/scripts
 
 auto_add_modules net
 
---------------------------------------------------------------------------------------------------------

Revision history for this message

Steven Haber (sthaber) wrote on 2013-04-09:

I've run into this issue as well. I'm writing a custom Live CD that boots over PXE using memdisk, and I was banging my head against the wall watching casper just search for "nice" block devices rather than using my image. At the very least, take it out of the man pages:

http://manpages.ubuntu.com/manpages/precise/en/man7/casper.7.html