362 lines
16 KiB
Diff
362 lines
16 KiB
Diff
From 789668deb3e6f8584ffab964d2204ddcb75f0a06 Mon Sep 17 00:00:00 2001
|
||
From: Frederick Grose <fgrose@sugarlabs.org>
|
||
Date: Mon, 20 Aug 2018 09:47:50 -0400
|
||
Subject: [PATCH] dmsquash-live: Support a flattened squashfs.img
|
||
|
||
A simplified root filesystem structure may be provided for OverlayFS
|
||
overlays by squashing the root filesystem directly instead of squashing
|
||
an embedded image file at /LiveOS/rootfs.img. Detect and configure
|
||
such a squashed root filesystem for live booting.
|
||
|
||
For OverlayFS boots, avoid the read-only Device-mapper linear device
|
||
at /dev/mapper/live-base.
|
||
Create a consistent device link at /dev/live-base for the read-only
|
||
base loop device for all overlayed live root filesystems.
|
||
Consistently provide a link at /dev/root for wait_for_dev.
|
||
|
||
Update documentation.
|
||
---
|
||
dracut.cmdline.7.asc | 126 +++++++++++++++---------
|
||
modules.d/90dmsquash-live/dmsquash-live-root.sh | 51 ++++++----
|
||
2 files changed, 110 insertions(+), 67 deletions(-)
|
||
|
||
diff --git a/dracut.cmdline.7.asc b/dracut.cmdline.7.asc
|
||
index df633e5d..882035af 100644
|
||
--- a/dracut.cmdline.7.asc
|
||
+++ b/dracut.cmdline.7.asc
|
||
@@ -838,23 +838,24 @@ Booting live images
|
||
Dracut offers multiple options for live booted images:
|
||
|
||
=====================
|
||
-SquashFS with read-only filesystem image::: The system will boot with a read
|
||
-only filesystem from the SquashFS and apply a writable device-mapper snapshot
|
||
-over the read only filesystem. Using this method ensures a relatively fast
|
||
-boot and lower RAM usage. Users **must be careful** to avoid writing too many
|
||
-blocks to the snapshot volume. Once the blocks of the snapshot overlay are
|
||
-exhausted, the root filesystem becomes read only and may cause application
|
||
-failures. The overlay file is marked 'Overflow', and a difficult recovery is
|
||
-required to repair and enlarge the overlay offline. Non-persistent overlays
|
||
-are sparse files in RAM that only consume content space as required blocks are
|
||
-allocated. They default to an apparent size of 32 GiB in RAM. The size can be
|
||
-adjusted with the **rd.live.overlay.size=** kernel command line option.
|
||
+SquashFS with read-only filesystem image::: The system will boot with a
|
||
+read-only filesystem from the SquashFS and apply a writable Device-mapper
|
||
+snapshot or an OverlayFS overlay mount for the read-only base filesystem. This
|
||
+method ensures a relatively fast boot and lower RAM usage. Users **must be
|
||
+careful** to avoid writing too many blocks to a snapshot volume. Once the
|
||
+blocks of the snapshot overlay are exhausted, the root filesystem becomes
|
||
+read-only and may cause application failures. The snapshot overlay file is
|
||
+marked 'Overflow', and a difficult recovery is required to repair and enlarge
|
||
+the overlay offline. Non-persistent overlays are sparse files in RAM that only
|
||
+consume content space as required blocks are allocated. They default to an
|
||
+apparent size of 32 GiB in RAM. The size can be adjusted with the
|
||
+**rd.live.overlay.size=** kernel command line option.
|
||
+
|
||
-The filesystem structure is expected to be:
|
||
+The filesystem structure is traditionally expected to be:
|
||
+
|
||
[listing]
|
||
--
|
||
-squashfs.img | Squashfs from LiveCD .iso downloaded via network
|
||
+squashfs.img | SquashFS from LiveCD .iso
|
||
!(mount)
|
||
/LiveOS
|
||
|- rootfs.img | Filesystem image to mount read-only
|
||
@@ -865,21 +866,35 @@ squashfs.img | Squashfs from LiveCD .iso downloaded via network
|
||
... |
|
||
--
|
||
+
|
||
-Dracut uses this method of live booting by default. No additional command line
|
||
-options are required other than **root=live:<URL>** to specify the location
|
||
-of your squashed filesystem.
|
||
+For OverlayFS mount overlays, the filesystem structure may also be a direct
|
||
+compression of the root filesystem:
|
||
++
|
||
+[listing]
|
||
+--
|
||
+squashfs.img | SquashFS from LiveCD .iso
|
||
+ !(mount)
|
||
+ /bin | Live filesystem
|
||
+ /boot |
|
||
+ /dev |
|
||
+ ... |
|
||
+--
|
||
++
|
||
+Dracut uses one of the overlay methods of live booting by default. No
|
||
+additional command line options are required other than **root=live:<URL>** to
|
||
+specify the location of your squashed filesystem.
|
||
+
|
||
- The compressed SquashFS image can be copied during boot to RAM at
|
||
`/run/initramfs/squashed.img` by using the **rd.live.ram=1** option.
|
||
-- A device with a persistent overlay can be booted read only by using the
|
||
+- A device with a persistent overlay can be booted read-only by using the
|
||
**rd.live.overlay.readonly** option on the kernel command line. This will
|
||
-cause a temporary, writable overlay to be stacked over a read-only snapshot
|
||
-of the root filesystem.
|
||
+either cause a temporary, writable overlay to be stacked over a read-only
|
||
+snapshot of the root filesystem or the OverlayFS mount will use an additional
|
||
+lower layer with the root filesystem.
|
||
+
|
||
Uncompressed live filesystem image:::
|
||
When the live system was installed with the '--skipcompress' option of the
|
||
__livecd-iso-to-disk__ installation script for Live USB devices, the root
|
||
-filesystem image, `rootfs.img`, is expanded on installation and no SquashFS
|
||
+filesystem image, __rootfs.img__, is expanded on installation and no SquashFS
|
||
is involved during boot.
|
||
+
|
||
- If **rd.live.ram=1** is used in this situation, the full, uncompressed
|
||
@@ -887,12 +902,12 @@ root filesystem is copied during boot to `/run/initramfs/rootfs.img` in the
|
||
`/run` tmpfs.
|
||
+
|
||
- If **rd.live.overlay=none** is provided as a kernel command line option,
|
||
-a writable, linear device-mapper target is created on boot with no overlay.
|
||
+a writable, linear Device-mapper target is created on boot with no overlay.
|
||
|
||
-writable filesystem image:::
|
||
+Writable filesystem image:::
|
||
The system will retrieve a compressed filesystem image, extract it to
|
||
`/run/initramfs/fsimg/rootfs.img`, connect it to a loop device, create a
|
||
-writable, linear device-mapper target at `/dev/mapper/live-rw`, and mount that
|
||
+writable, linear Device-mapper target at `/dev/mapper/live-rw`, and mount that
|
||
as a writable volume at `/`. More RAM is required during boot but the live
|
||
filesystem is easier to manage if it becomes full. Users can make a filesystem
|
||
image of any size and that size will be maintained when the system boots. There
|
||
@@ -902,7 +917,7 @@ The filesystem structure is expected to be:
|
||
+
|
||
[listing]
|
||
--
|
||
-rootfs.tgz | Compressed tarball containing fileystem image
|
||
+rootfs.tgz | Compressed tarball containing filesystem image
|
||
!(unpack)
|
||
/rootfs.img | Filesystem image at /run/initramfs/fsimg/
|
||
!(mount)
|
||
@@ -930,11 +945,11 @@ NOTE: There must be enough free RAM available to hold the complete image.
|
||
This method is very suitable for diskless boots.
|
||
|
||
**root=**live:__<url>__::
|
||
-Boots a live image retrieved from __<url>__. Requires dracut 'livenet' module.
|
||
-Valid handlers: __http, https, ftp, torrent, tftp__.
|
||
+Boots a live image retrieved from __<url>__. Requires the dracut 'livenet'
|
||
+module. Valid handlers: __http, https, ftp, torrent, tftp__.
|
||
+
|
||
[listing]
|
||
-.Example
|
||
+.Examples
|
||
--
|
||
root=live:http://example.com/liveboot.img
|
||
root=live:ftp://ftp.example.com/liveboot.img
|
||
@@ -946,7 +961,7 @@ Enables debug output from the live boot process.
|
||
|
||
**rd.live.dir=**__<path>__::
|
||
Specifies the directory within the boot device where the squashfs.img or
|
||
-rootfs.img can be found. By default, this is __LiveOS__.
|
||
+rootfs.img can be found. By default, this is `/LiveOS`.
|
||
|
||
**rd.live.squashimg=**__<filename of SquashFS image>__::
|
||
Specifies the filename for a SquashFS image of the root filesystem.
|
||
@@ -954,35 +969,52 @@ By default, this is __squashfs.img__.
|
||
|
||
**rd.live.ram=**1::
|
||
Copy the complete image to RAM and use this for booting. This is useful
|
||
-when the image resides on, i.e., a DVD which needs to be ejected later on.
|
||
+when the image resides on, e.g., a DVD which needs to be ejected later on.
|
||
|
||
**rd.live.overlay={**__<devspec>__[:__{<pathspec>|auto}__]|__none__}::
|
||
-Allow the usage of a permanent overlay.
|
||
-- _<devspec>_ specifies the path to a device with a mountable filesystem.
|
||
-- _<pathspec>_ is the path to a file within that filesystem, which shall be
|
||
+Manage the usage of a permanent overlay.
|
||
++
|
||
+--
|
||
+* _<devspec>_ specifies the path to a device with a mountable filesystem.
|
||
+* _<pathspec>_ is the path to a file within that filesystem, which shall be
|
||
used to persist the changes made to the device specified by the
|
||
**root=live:__<url>__** option.
|
||
-- _none_ specifies no overlay when an uncompressed live root filesystem is
|
||
-available.
|
||
-If a persistent overlay is detected at the standard LiveOS path, the overlay &
|
||
-overlay type detected (whether Device-mapper or OverlayFS) will be used.
|
||
++
|
||
+The default _pathspec_, when _auto_ or no _:<pathspec>_ is given, is
|
||
+`/<+++<b>rd.live.dir</b>+++>/overlay-<label>-<uuid>`, where _<label>_ is the
|
||
+device LABEL, and _<uuid>_ is the device UUID.
|
||
+* _none_ (the word itself) specifies that no overlay will be used, such as when
|
||
+an uncompressed, writable live root filesystem is available.
|
||
++
|
||
+If a persistent overlay __is detected__ at the standard LiveOS path, the
|
||
+overlay & overlay type detected, whether Device-mapper or OverlayFS, will be
|
||
+used.
|
||
+--
|
||
+
|
||
[listing]
|
||
-.Example
|
||
+.Examples
|
||
--
|
||
rd.live.overlay=/dev/sdb1:persistent-overlay.img
|
||
+rd.live.overlay=UUID=99440c1f-8daa-41bf-b965-b7240a8996f4
|
||
--
|
||
|
||
**rd.live.overlay.size=**__<size_MiB>__::
|
||
-Specifies a non-persistent overlay size in MiB. The default is _32768_.
|
||
+Specifies a non-persistent Device-mapper overlay size in MiB. The default is
|
||
+_32768_.
|
||
|
||
**rd.live.overlay.readonly=**1::
|
||
-Specifies a non-persistent, writable snapshot overlay to be stacked over a
|
||
-read-only snapshot of the root filesystem, `/dev/mapper/live-ro`, or a read-
|
||
-only loop device of a writable `rootfs.img`.
|
||
+This is used to boot with a normally read-write persistent overlay in a
|
||
+read-only mode. With this option, either an additional, non-persistent,
|
||
+writable snapshot overlay will be stacked over a read-only snapshot,
|
||
+`/dev/mapper/live‑ro`, of the base filesystem with the persistent overlay, or a
|
||
+read-only loop device, in the case of a writable __rootfs.img__, or an OverlayFS
|
||
+mount will use the persistent overlay directory linked at `/run/overlayfs‑r` as
|
||
+an additional lower layer along with the base root filesystem and apply a
|
||
+transient, writable upper directory overlay, in order to complete the booted
|
||
+root filesystem.
|
||
|
||
**rd.live.overlay.reset=**1::
|
||
-Specifies that a persistent overlay should be reset on boot. All root
|
||
+Specifies that a persistent overlay should be reset on boot. All previous root
|
||
filesystem changes are vacated by this action.
|
||
|
||
**rd.live.overlay.thin=**1::
|
||
@@ -993,25 +1025,25 @@ that memory is given back to the kernel when the filesystem does not claim it
|
||
anymore.
|
||
|
||
**rd.live.overlay.overlayfs=**1::
|
||
-Enables the use of the **OverlayFS** kernel module, if available, to provide a
|
||
+Enables the use of the *OverlayFS* kernel module, if available, to provide a
|
||
copy-on-write union directory for the root filesystem. OverlayFS overlays are
|
||
directories of the files that have changed on the read-only base (lower)
|
||
filesystem. The root filesystem is provided through a special overlay type
|
||
mount that merges the lower and upper directories. If an OverlayFS upper
|
||
directory is not present on the boot device, a tmpfs directory will be created
|
||
-at /run/overlayfs to provide temporary storage. Persistent storage can be
|
||
+at `/run/overlayfs` to provide temporary storage. Persistent storage can be
|
||
provided on vfat or msdos formatted devices by supplying the OverlayFS upper
|
||
directory within an embedded filesystem that supports the creation of trusted.*
|
||
extended attributes and provides a valid d_type in readdir responses, such as
|
||
with ext4 and xfs. On non-vfat-formatted devices, a persistent OverlayFS
|
||
overlay can extend the available root filesystem storage up to the capacity of
|
||
-the LiveOS device.
|
||
+the LiveOS disk device.
|
||
+
|
||
If a persistent overlay is detected at the standard LiveOS path, the overlay &
|
||
-overlay type detected (whether OverlayFS or Device-mapper) will be used.
|
||
+overlay type detected, whether OverlayFS or Device-mapper, will be used.
|
||
+
|
||
The **rd.live.overlay.readonly** option, which allows a persistent overlayfs to
|
||
-be mounted read only through a higher level transient overlay directory, has
|
||
+be mounted read-only through a higher level transient overlay directory, has
|
||
been implemented through the multiple lower layers feature of OverlayFS.
|
||
|
||
|
||
diff --git a/modules.d/90dmsquash-live/dmsquash-live-root.sh b/modules.d/90dmsquash-live/dmsquash-live-root.sh
|
||
index ac603408..0c5e010e 100755
|
||
--- a/modules.d/90dmsquash-live/dmsquash-live-root.sh
|
||
+++ b/modules.d/90dmsquash-live/dmsquash-live-root.sh
|
||
@@ -250,13 +250,11 @@ do_live_overlay() {
|
||
echo 0 $sz snapshot $base $over PO 8 | dmsetup create live-rw
|
||
fi
|
||
|
||
- # Create a device that always points to a ro base image
|
||
- if [ -n "$overlayfs" ]; then
|
||
- BASE_LOOPDUP=$(losetup -f --show -r $BASE_LOOPDEV)
|
||
- echo 0 $sz linear $BASE_LOOPDUP 0 | dmsetup create --readonly live-base
|
||
- else
|
||
+ # Create a device for the ro base of overlayed file systems.
|
||
+ if [ -z "$overlayfs" ]; then
|
||
echo 0 $sz linear $BASE_LOOPDEV 0 | dmsetup create --readonly live-base
|
||
fi
|
||
+ ln -s $BASE_LOOPDEV /dev/live-base
|
||
}
|
||
|
||
# we might have a genMinInstDelta delta file for anaconda to take advantage of
|
||
@@ -291,10 +289,21 @@ if [ -e "$SQUASHED" ]; then
|
||
mkdir -m 0755 -p /run/initramfs/squashfs
|
||
mount -n -t squashfs -o ro $SQUASHED_LOOPDEV /run/initramfs/squashfs
|
||
|
||
- if [ -f /run/initramfs/squashfs/LiveOS/rootfs.img ]; then
|
||
- FSIMG="/run/initramfs/squashfs/LiveOS/rootfs.img"
|
||
- elif [ -f /run/initramfs/squashfs/LiveOS/ext3fs.img ]; then
|
||
- FSIMG="/run/initramfs/squashfs/LiveOS/ext3fs.img"
|
||
+ if [ -d /run/initramfs/squashfs/LiveOS ]; then
|
||
+ if [ -f /run/initramfs/squashfs/LiveOS/rootfs.img ]; then
|
||
+ FSIMG="/run/initramfs/squashfs/LiveOS/rootfs.img"
|
||
+ elif [ -f /run/initramfs/squashfs/LiveOS/ext3fs.img ]; then
|
||
+ FSIMG="/run/initramfs/squashfs/LiveOS/ext3fs.img"
|
||
+ fi
|
||
+ elif [ -d /run/initramfs/squashfs/proc ]; then
|
||
+ FSIMG=$SQUASHED
|
||
+ if [ -z "$overlayfs" ]; then
|
||
+ overlayfs="yes"
|
||
+ [ -n "$DRACUT_SYSTEMD" ] && reloadsysrootmountunit="yes"
|
||
+ fi
|
||
+ else
|
||
+ die "Failed to find a root filesystem in $SQUASHED."
|
||
+ exit 1
|
||
fi
|
||
else
|
||
# we might have an embedded fs image to use as rootfs (uncompressed live)
|
||
@@ -312,8 +321,8 @@ else
|
||
fi
|
||
fi
|
||
|
||
-if [ -n "$FSIMG" ] ; then
|
||
- if [ -n "$writable_fsimg" ] ; then
|
||
+if [ -n "$FSIMG" ]; then
|
||
+ if [ -n "$writable_fsimg" ]; then
|
||
# mount the provided filesystem read/write
|
||
echo "Unpacking live filesystem (may take some time)" > /dev/kmsg
|
||
mkdir -m 0755 /run/initramfs/fsimg/
|
||
@@ -336,9 +345,13 @@ if [ -n "$FSIMG" ] ; then
|
||
setup=yes
|
||
fi
|
||
fi
|
||
- BASE_LOOPDEV=$(losetup -f --show $opt $FSIMG)
|
||
- sz=$(blockdev --getsz $BASE_LOOPDEV)
|
||
- if [ "$setup" == rw ]; then
|
||
+ if [ "$FSIMG" = "$SQUASHED" ]; then
|
||
+ BASE_LOOPDEV=$SQUASHED_LOOPDEV
|
||
+ else
|
||
+ BASE_LOOPDEV=$(losetup -f --show $opt $FSIMG)
|
||
+ sz=$(blockdev --getsz $BASE_LOOPDEV)
|
||
+ fi
|
||
+ if [ "$setup" = rw ]; then
|
||
echo 0 $sz linear $BASE_LOOPDEV 0 | dmsetup create live-rw
|
||
else
|
||
# Add a DM snapshot or OverlayFS for writes.
|
||
@@ -346,8 +359,6 @@ if [ -n "$FSIMG" ] ; then
|
||
fi
|
||
fi
|
||
|
||
-[ -e "$SQUASHED" ] && [ -z "$overlayfs" ] && umount -l /run/initramfs/squashfs
|
||
-
|
||
if [ -b "$OSMIN_LOOPDEV" ]; then
|
||
# set up the devicemapper snapshot device, which will merge
|
||
# the normal live fs image, and the delta, into a minimzied fs image
|
||
@@ -380,17 +391,17 @@ if [ -n "$overlayfs" ]; then
|
||
'lowerdir=/run/rootfsbase,upperdir=/run/overlayfs,workdir=/run/ovlwork' \
|
||
"$NEWROOT" > $hookdir/mount/01-$$-live.sh
|
||
fi
|
||
- _dev=/run/rootfsbase
|
||
else
|
||
- _dev=/dev/mapper/live-rw
|
||
if [ -z "$DRACUT_SYSTEMD" ]; then
|
||
[ -n "$ROOTFLAGS" ] && ROOTFLAGS="-o $ROOTFLAGS"
|
||
printf 'mount %s /dev/mapper/live-rw %s\n' "$ROOTFLAGS" "$NEWROOT" > $hookdir/mount/01-$$-live.sh
|
||
fi
|
||
- ln -s $BASE_LOOPDEV /run/rootfsbase
|
||
fi
|
||
-ln -s $_dev /dev/root
|
||
+[ -e "$SQUASHED" ] && umount -l /run/initramfs/squashfs
|
||
+
|
||
+ln -s null /dev/root
|
||
|
||
need_shutdown
|
||
|
||
exit 0
|
||
+
|
||
|