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scritps/btrsnp
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scritps/btrsnp
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#!/bin/sh
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# Create a BTRFS snapshot of a subvolume
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# This script is possibly highly specific to my current BTRFS setup and may not
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# work the way you want it to for your system
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# My current (2021-09-27) BTRFS is as follows:
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# BTRFS Partition (mounted to /mnt/nvme0n1p2 for easy access to subvolumes)
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# - gentoo (mounted either to / or /mnt/gentoo)
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# - home (mounted to /home)
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# - sys-misc (mounted to /mnt/sys-misc)
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# - void (mounted either to / or /mnt/void)
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# Snapshots will be saved with the name `SUBVOLUMENAME-$(date +%F-%H_$M_%S)`
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[ "$BTRSNP_DEVICE" ] || BTRSNP_DEVICE=$(findmnt -nvo SOURCE /)
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[ "$BTRSNP_READ" ] || BTRSNP_READ=ro
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[ "$BTRSNP_SUBVOL" ] || {
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BTRSNP_SUBVOL=$(findmnt -no SOURCE /)
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BTRSNP_SUBVOL=${BTRSNP_SUBVOL##*/}
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BTRSNP_SUBVOL=${BTRSNP_SUBVOL%]}
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}
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usage() {
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while read -r line
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do printf '%b\n' "$line"
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done <<-USAGE
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usage: ${0##*/} [OPTIONS]
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options:
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\t-d DEVICE - select which partition the subvolume is on
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\t-h - displays this message
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\t-r [ro|rw] - determine if the snapshot should be readonly
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\t-s SUBVOL - select which subvolume to snapshot
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environment variables:
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\tBTRSNP_DEVICE - selects which partition the subvolume is on
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\t defaults to the root partition
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\tBTRSNP_READ - determine if the snapshot should be readonly
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\t defaults to \`ro\`
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\tBTRSNP_SUBVOL - selects which subvolume to snapshot
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\t defaults to the subvolume mounted at as /
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USAGE
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exit "${1:-1}"
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}
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msg() {
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case $1 in
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e ) printf '%b\n' "${0##*/}: $*" 1>&2 ;;
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* ) printf '%b\n' "${0##*/}: $*" ;;
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esac
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}
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while [ "$*" ]
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do
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case $1 in
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- ) shift; continue ;;
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-- ) shift; break ;;
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-* ) flag=${1#-}; shift ;;
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* ) shift; continue ;;
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esac
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while [ "$flag" ]
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do
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arg=${flag%"${flag#?}"}
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case $arg in
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d ) BTRSNP_DEVICE="$1"; shift ;;
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h ) usage 0 ;;
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s ) BTRSNP_SUBVOL="$1"; shift ;;
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r )
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[ "$1" ] || BTRSNP_READ="rw" && {
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case $1 in
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ro ) BTRSNP_READ="ro" ;;
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rw ) BTRSNP_READ="rw" ;;
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* ) msg e "$1: invalid option argument for -$arg"; usage 1 ;;
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esac
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shift
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}
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;;
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* ) msg e "-$arg: invalid argument"; usage 1 ;;
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esac
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flag=${flag#?}
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done
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done
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# shellcheck disable=SC2015
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[ "$BTRSNP_DEVICE" ] && [ "$BTRSNP_SUBVOL" ] || {
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msg e "a device and subvolume are required"
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usage 1
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}
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# Look for the raw BTRFS mount in /mnt this may be changeable in the future
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BTRSNP_DEVICE=${BTRSNP_DEVICE##*/}
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if findmnt "/mnt/$BTRSNP_DEVICE" > /dev/null 2>&1
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then btrfs_partition_path=/mnt/$BTRSNP_DEVICE
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else
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msg e "BTRFS partition is not mounted at /mnt/$BTRSNP_DEVICE"
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exit 1
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fi
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# If I find a more accurate way to check if a directory is a subvolume I will implement it, but for
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# now, just check if it's a directory
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if [ -d "$btrfs_partition_path/$BTRSNP_SUBVOL" ]
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then btrfs_subvolume_path="$btrfs_partition_path/$BTRSNP_SUBVOL"
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else
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msg e "This is not a BTRFS subvolume"
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exit 1
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fi
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case $BTRSNP_READ in
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ro ) ro="-r" ;;
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rw ) ;;
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esac
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btrfs subvolume snapshot $ro "$btrfs_subvolume_path" \
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"${btrfs_subvolume_path}-$(date +'%F-%H_%M_%S')"