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45 lines
1.3 KiB
45 lines
1.3 KiB
#!/bin/sh
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#
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# Helper script for using a diskfile for the LOWER or UPPER+WORK
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# filesystems.
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#
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# Example use a whole diskfile filesystem as LOWER:
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# LOWER=!overlay-diskfile mnt/ disk.img
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#
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# Example use a diskfile partition 2 as LOWER:
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# LOWER=!overlay-diskfile mnt/ disk.img 2
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#
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# Example use a subtree of a diskfile partition 2 as LOWER:
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# LOWER=!overlay-diskfile mnt/some/path disk.img 2
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#
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# Example use a while diskfile as UPPER and WORK.
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# The diskfile is mounted on "mnt".
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# UPPER=!overlay-diskfile mnt/some/upper/path disk.img 2
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# WORK= mnt/some/work/path
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# Helper function to determine the mount offset for the partition, if any
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partoffset() {
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local X
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if [ -z "$2" ] ; then
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echo 0
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else
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fdisk -lo Start "$1" | grep -A$2 '^ Start' | \
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sed '${s|^|512*|;b};d' | bc -l
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fi
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}
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# Only do something when invoked by overlay-boot
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if [ "$ACTION" = "overlay-boot" ] ; then
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DISKFILE="$2"
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# .. and a diskfile is given
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if [ -n "$DISKFILE" ] ; then
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MOUNTPOINT="$(realpath "${1%/*}")"
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PARTITIONINDEX="$3"
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# .. and it's not mounted yet (for this subhost)
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if ! grep -qE "^[^ ]* $MOUNTPOINT" /proc/mounts ; then
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OFFSET=$(partoffset "$DISKFILE" "$PARTITIONINDEX")
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mount -ooffset=$OFFSET "$DISKFILE" "$MOUNTPOINT" || exit 1
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fi
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fi
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fi
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echo "${1#/}"
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