Blame SOURCES/0259-Adding-support-for-read-write-filesystem-images.patch

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From b9c6d2b2afa94dcba7129390edb7b1a2eaf2c31c Mon Sep 17 00:00:00 2001
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From: Major Hayden <major@mhtx.net>
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Date: Mon, 4 Aug 2014 10:27:36 -0500
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Subject: [PATCH] Adding support for read/write filesystem images
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A user can provide a filesystem image (rootfs.img) inside a compressed
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tarball and that filesystem image will be mounted read/write.  This provides
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some benefits over a device mapper snapshot overlay, especially when the
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live system becomes full.  The boot command line simple needs
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"rd.writable.fsimg" added to utilize this feature.
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Additional documentation for this option as well as other live boot
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options is included.
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Signed-off-by: Major Hayden <major@mhtx.net>
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(cherry picked from commit 504c0a8feca7d7ef470e4483a68cbaf9cb7df2bf)
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---
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 dracut.cmdline.7.asc                            | 82 ++++++++++++++++++++++++-
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 modules.d/90dmsquash-live/dmsquash-live-root.sh | 16 ++++-
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 modules.d/90dmsquash-live/module-setup.sh       |  2 +-
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 3 files changed, 96 insertions(+), 4 deletions(-)
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diff --git a/dracut.cmdline.7.asc b/dracut.cmdline.7.asc
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index bce86084..0493dcd8 100644
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--- a/dracut.cmdline.7.asc
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+++ b/dracut.cmdline.7.asc
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@@ -729,10 +729,90 @@ rd.znet=qeth,0.0.0600,0.0.0601,0.0.0602,layer2=1,portname=foo
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 rd.znet=ctc,0.0.0600,0.0.0601,protocol=bar
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 --
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+Booting live images
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+~~~~~~~~~~~~~~~~~~~
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+Dracut offers multiple options for live booted images:
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+
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+=====================
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+squashfs with read-only filesystem image::: The system will boot with a read
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+only filesystem from the squashfs and apply a writable device mapper snapshot
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+over the read only filesystem.  Using this method ensures a relatively fast
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+boot and lower RAM usage. Users **must be careful** to avoid writing too many
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+blocks to the snapshot volume.  Once the blocks of the snapshot are exhaused,
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+the live filesystem becomes unusable and requires a reboot.
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++
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+The filesystem structure is expected to be:
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++
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+[listing]
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+--
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+squashfs.img          |  Squashfs downloaded via network
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+   !(mount)
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+   /LiveOS
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+       |- ext3fs.img  |  Filesystem image to mount read-only
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+            !(mount)
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+            /bin      |  Live filesystem
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+            /boot     |
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+            /dev      |
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+            ...       |
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+--
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++
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+Dracut uses this method of live booting by default.  No additional command line
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+options are required other than **root=live:<URL>** to specify the location
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+of your squashed filesystem.
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++
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+writable filesystem image::: The system will retrieve a compressed filesystem
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+image, connect it to a loopback device, and mount it as a writable volume.  More
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+RAM is required during boot but the live filesystem is easier to manage if it
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+becomes full.  Users can make a filesystem image of any size and that size will
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+be maintained when the system boots.
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++
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+The filesystem structure is expected to be:
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++
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+[listing]
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+--
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+rootfs.tgz            |  Compressed tarball containing fileystem image
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+   !(unpack)
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+   /rootfs.img        |  Filesystem image
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+      !(mount)
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+      /bin            |  Live filesystem
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+      /boot           |
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+      /dev            |
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+      ...             |
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+--
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++
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+To use this boot option, ensure that **rd.writable_fsimg=1** is in your kernel
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+command line and add the **root=live:<URL>** to specify the location
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+of your compressed filesystem image tarball.
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+=====================
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+
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+**root=**live:__<url>__::
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+Boots a live image retrieved from __<url>__.  Valid handlers: __http, httpd, ftp, tftp__.
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++
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+[listing]
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+.Example
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+--
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+root=live:http://example.com/liveboot.img
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+root=live:ftp://ftp.example.com/liveboot.img
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+--
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+
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+**rd.live.debug=**1::
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+Enables debug output from the live boot process.
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+
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+**rd.live.dir=**__<path>__::
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+Specifies the directory within the squashfs where the ext3fs.img or rootfs.img
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+can be found.  By default, this is __LiveOS__.
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+
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+**rd.writable.fsimg=**1::
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+Enables writable filesystem support.  The system will boot with a fully 
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+writable filesystem without snapshots __(see notes above about available live boot options)__.
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+You can use the **rootflags** option to set mount options for the live
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+filesystem as well __(see documentation about rootflags in the **Standard** section above)__.
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+
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+
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 Plymouth Boot Splash
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 ~~~~~~~~~~~~~~~~~~~~
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 **plymouth.enable=0**::
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-    disable the plymouth bootsplash completly.
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+    disable the plymouth bootsplash completely.
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 **rd.plymouth=0**::
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     disable the plymouth bootsplash only for the initramfs.
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diff --git a/modules.d/90dmsquash-live/dmsquash-live-root.sh b/modules.d/90dmsquash-live/dmsquash-live-root.sh
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index 5705e8df..c6c02c74 100755
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--- a/modules.d/90dmsquash-live/dmsquash-live-root.sh
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+++ b/modules.d/90dmsquash-live/dmsquash-live-root.sh
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@@ -4,6 +4,8 @@
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 type getarg >/dev/null 2>&1 || . /lib/dracut-lib.sh
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+command -v unpack_archive >/dev/null || . /lib/img-lib.sh
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+
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 PATH=/usr/sbin:/usr/bin:/sbin:/bin
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 if getargbool 0 rd.live.debug -n -y rdlivedebug; then
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@@ -26,6 +28,7 @@ getargbool 0 rd.live.ram -d -y live_ram && live_ram="yes"
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 getargbool 0 rd.live.overlay.reset -d -y reset_overlay && reset_overlay="yes"
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 getargbool 0 rd.live.overlay.readonly -d -y readonly_overlay && readonly_overlay="--readonly" || readonly_overlay=""
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 overlay=$(getarg rd.live.overlay -d overlay)
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+getargbool 0 rd.writable.fsimg -d -y writable_fsimg && writable_fsimg="yes"
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 # CD/DVD media check
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 [ -b $livedev ] && fs=$(blkid -s TYPE -o value $livedev)
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@@ -180,9 +183,18 @@ fi
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 if [ -n "$FSIMG" ] ; then
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     BASE_LOOPDEV=$( losetup -f )
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-    losetup -r $BASE_LOOPDEV $FSIMG
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-    do_live_from_base_loop
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+    if [ -n "$writable_fsimg" ] ; then
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+        # mount the provided fileysstem read/write
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+        echo "Unpacking live filesystem (may take some time)"
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+        unpack_archive $FSIMG /tmp/fsimg/
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+        losetup $BASE_LOOPDEV /tmp/fsimg/rootfs.img
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+        echo "0 $( blockdev --getsize $BASE_LOOPDEV ) linear $BASE_LOOPDEV 0" | dmsetup create live-rw
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+    else
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+        # mount the filesystem read-only and add a dm snapshot for writes
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+        losetup -r $BASE_LOOPDEV $FSIMG
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+        do_live_from_base_loop
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+    fi
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 fi
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 # we might have an embedded fs image on squashfs (compressed live)
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diff --git a/modules.d/90dmsquash-live/module-setup.sh b/modules.d/90dmsquash-live/module-setup.sh
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index c6d1f9d5..f52717de 100755
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--- a/modules.d/90dmsquash-live/module-setup.sh
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+++ b/modules.d/90dmsquash-live/module-setup.sh
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@@ -11,7 +11,7 @@ check() {
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 depends() {
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     # if dmsetup is not installed, then we cannot support fedora/red hat
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     # style live images
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-    echo dm rootfs-block
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+    echo dm rootfs-block img-lib
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     return 0
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 }
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