commit a2790a0a38f04e76f6dafb862baa7b74502762fc · yemou.pink/scripts

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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')"