Optimizing OverlayFS module with new IFS separator and new supported mode. (#10321)
Authored-by: lanzeliu <lanzeliu@microsoft.com>
This commit is contained in:
Lanze Liu
GitHub
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ae193e0202
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@ -2,9 +2,9 @@
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# Copyright (c) Microsoft Corporation.
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# Licensed under the MIT License.
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# Description: This script is designed to mount a DM-Verity root filesystem and
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# set up OverlayFS. It is driven by kernel parameters and is invoked during the
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# dracut initramfs phase.
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# Description: This script is designed to set up OverlayFS. It also works with
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# DM-Verity environment. It is driven by kernel parameters and is invoked during
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# the dracut initramfs phase.
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# Kernel Parameters:
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# - root: Specifies the path to the root filesystem. This script is designed to
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@ -14,29 +14,28 @@
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# setups, the script will proceed with the standard OverlayFS setup, ensuring
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# versatility in its application.
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# - rd.overlayfs: A comma-separated list defining the OverlayFS configuration.
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# Each entry should specify the overlay, upper, work directories, and optional
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# volume for an OverlayFS instance.
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# Each entry should specify the lower, upper, work directories, optional
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# volume, and optional mount mode for an OverlayFS instance.
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# Behavior:
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# - Verifies the presence of the 'dracut-lib' for necessary utilities.
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# - Mounts the DM-Verity root filesystem as read-only at a predefined mount
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# point.
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# point or mount the root device at a predefined mount point.
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# - Sets up the OverlayFS based on the provided kernel parameters. If a
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# persistent volume is specified, it's used as the upper layer for the
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# OverlayFS; otherwise, a volatile overlay is created.
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# - Mounts the OverlayFS on top of the root filesystem, merging the read-only
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# root with the writable overlay, allowing system modifications without
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# altering the base system.
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# - Mounts the OverlayFS on top of the root filesystem, merging the root with
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# the writable overlay, allowing system modifications without altering the
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# base system.
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parse_kernel_cmdline_args() {
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# Ensure that the 'dracut-lib' is present and loaded.
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type getarg >/dev/null 2>&1 || . /lib/dracut-lib.sh
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type getarg > /dev/null 2>&1 || . /lib/dracut-lib.sh
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VERITY_MOUNT="/mnt/verity_mnt"
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ROOT_VERITY_MOUNTPOINT="/mnt/root_verity_mnt"
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OVERLAY_MOUNT="/mnt/overlay_mnt"
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OVERLAY_MNT_OPTS="rw,nodev,nosuid,nouser,noexec"
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# Retrieve the verity root. It is expected to be predefined by the dracut cmdline module.
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# Retrieve the root device.
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[ -z "$root" ] && root=$(getarg root=)
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# Check if we're in a dm-verity environment and the root variable matches
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# the expected path. The path "/dev/mapper/root" is hardcoded here because
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@ -63,7 +62,7 @@ mount_volatile_persistent_volume() {
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if [[ "${_volume}" == "volatile" ]]; then
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# Fallback to volatile overlay if no persistent volume is specified.
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echo "No overlayfs persistent volume specified. Creating a volatile overlay."
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mount -t tmpfs tmpfs -o ${OVERLAY_MNT_OPTS} "${_overlay_mount}" || \
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mount -t tmpfs tmpfs "${_overlay_mount}" || \
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die "Failed to create overlay tmpfs at ${_overlay_mount}"
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else
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# Check if the specified Overlay RAID volume is present in the system.
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@ -83,64 +82,72 @@ create_overlayfs() {
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local _lower=$1
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local _upper=$2
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local _work=$3
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local _mode=$4
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[ -d "$_lower" ] || die "Unable to create overlay as $_lower does not exist"
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mkdir -p "${_upper}" && \
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mkdir -p "${_work}" && \
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mount -t overlay overlay -o ro,lowerdir="${_lower}",upperdir="${_upper}",workdir="${_work}" "${_lower}" || \
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mkdir -p "${_upper}" || die "Failed to create upper directory ${_upper}"
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mkdir -p "${_work}" || die "Failed to create work directory ${_work}"
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# Note for now, the mountpoint / mergedir is set to the same directory as the lowerdir.
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# This means the overlay will be mounted directly on the lower directory.
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# TODO: Add support for a customized mountpoint in future versions.
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mount -t overlay overlay -o "${_mode}",lowerdir="${_lower}",upperdir="${_upper}",workdir="${_work}" "${_lower}" || \
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die "Failed to mount overlay in ${_lower}"
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}
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mount_overlayfs() {
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local cnt=0
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local overlay_mount_with_cnt
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local volume_mount_with_cnt
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declare -A volume_mount_map
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mkdir -p "${ROOT_VERITY_MOUNTPOINT}"
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if [ "$is_verity" = true ]; then
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echo "Mounting DM-Verity Target"
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mkdir -p "${VERITY_MOUNT}"
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mount -o ro,defaults "/dev/mapper/root" "${VERITY_MOUNT}" || \
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mount -o ro "/dev/mapper/root" "${ROOT_VERITY_MOUNTPOINT}" || \
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die "Failed to mount dm-verity root target"
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else
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echo "Mounting regular root"
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mkdir -p "${VERITY_MOUNT}"
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# Remove 'block:' prefix if present.
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root_device=$(expand_persistent_dev "${root#block:}")
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mount -o ro,defaults "$root_device" "${VERITY_MOUNT}" || \
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mount "$root_device" "${ROOT_VERITY_MOUNTPOINT}" || \
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die "Failed to mount root"
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fi
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echo "Starting to create OverlayFS"
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for _group in ${overlayfs}; do
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IFS=',' read -r overlay upper work volume <<< "$_group"
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IFS=';' read -ra overlay_groups <<< "$overlayfs"
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for _group in "${overlay_groups[@]}"; do
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IFS=',' read -r lower upper work volume mode <<< "$_group"
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# Set mode as ro to fulfill Trident specific requirement.
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mode=${mode:-ro}
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# Resolve volume to its full device path.
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volume=$(expand_persistent_dev "$volume")
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if [[ "$volume" == "" ]]; then
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overlay_mount_with_cnt="${OVERLAY_MOUNT}/${cnt}"
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mount_volatile_persistent_volume "volatile" $overlay_mount_with_cnt
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volume_mount_with_cnt="${OVERLAY_MOUNT}/${cnt}"
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mount_volatile_persistent_volume "volatile" $volume_mount_with_cnt
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else
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if [[ -n "${volume_mount_map[$volume]}" ]]; then
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# Volume already mounted, retrieve existing mount point from map.
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overlay_mount_with_cnt=${volume_mount_map[$volume]}
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volume_mount_with_cnt=${volume_mount_map[$volume]}
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else
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# Not in map, so mount and update the map.
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overlay_mount_with_cnt="${OVERLAY_MOUNT}/${cnt}"
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mount_volatile_persistent_volume $volume $overlay_mount_with_cnt
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volume_mount_map[$volume]=$overlay_mount_with_cnt
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volume_mount_with_cnt="${OVERLAY_MOUNT}/${cnt}"
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mount_volatile_persistent_volume $volume $volume_mount_with_cnt
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volume_mount_map[$volume]=$volume_mount_with_cnt
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fi
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fi
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cnt=$((cnt + 1))
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echo "Creating OverlayFS with overlay: $overlay, upper: ${overlay_mount_with_cnt}/${upper}, work: ${overlay_mount_with_cnt}/${work}"
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create_overlayfs "${VERITY_MOUNT}/${overlay}" "${overlay_mount_with_cnt}/${upper}" "${overlay_mount_with_cnt}/${work}"
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echo "Creating OverlayFS with lower: $lower, upper: ${volume_mount_with_cnt}/${upper}, work: ${volume_mount_with_cnt}/${work}, mode: ${mode}"
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create_overlayfs "${ROOT_VERITY_MOUNTPOINT}/${lower}" "${volume_mount_with_cnt}/${upper}" "${volume_mount_with_cnt}/${work}" "${mode}"
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cnt=$((cnt + 1))
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done
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echo "Done Verity Root Mounting and OverlayFS Mounting"
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# Re-mount the verity mount along with overlayfs to the sysroot.
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mount --rbind "${VERITY_MOUNT}" "${NEWROOT}"
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mount --rbind "${ROOT_VERITY_MOUNTPOINT}" "${NEWROOT}"
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}
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# Keep a copy of this function here from verity-read-only-root package.
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@ -10,6 +10,6 @@
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"lgpl-2.1.txt": "dc626520dcd53a22f727af3ee42c770e56c97a64fe3adb063799d8ab032fe551",
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"megaraid.conf": "914824cdbe0c525b71efa05a75e453335b0068beb8bc28bef2a5866d74bf7dd4",
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"module-setup.sh": "8f5a0d3cc393d78bcb523b0d53c578d2767d688f00e84b525355bbb31d753da4",
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"overlayfs-mount.sh": "f049d0ad2e4a1d98acb329765900690883520fdc8fc9463f5081f6e7fb679695"
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"overlayfs-mount.sh": "28f47c107a4435c5153bdb5b2f92f20b7a75bf3932216635ee810875c27dd55b"
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}
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}
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