snap

#
# Snap is a utility to create system snapshots for btrfs subvolumes.
# 
# @author Mubeen Iqbal
# @date 2014-11-26
# @license GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
#

#!/bin/sh

# The total subvolumes for which a snapshot will be created.
totalSubvolumes=3

# Source subvolumes array (create snapshot of these).
sourceSubvolumes=(
    "/run/btrfs-root/arch/__active/rootvol"
    "/run/btrfs-root/data/__active/home"
    "/run/btrfs-root/data/__active/var"
)

# Source subvolume mount points.
mountPoints=(
    "/"
    "/home"
    "/var"
)

# Snapshots directory.
snapshotDir="/run/btrfs-root/data/__snapshot"

# Snapshot names array.
snapshotNames=(
    "rootvol"
    "home"
    "var"
)

# Record date and time for the snapshot.
# The date must be recorded only once to avoid any time differences.
dt="$(date +%Y-%m-%d_%H-%M-%S)"
d="$(echo "${dt}" | cut -d '_' -f1)"
t="$(echo "${dt}" | cut -d '_' -f2)"
dateTime=""${d}"-"${t}""

# Readme file info.
readmeFileName="readme.txt"
readmeFilePath=""${snapshotDir}"/"${dateTime}"/"${readmeFileName}""

# Variable to hold a user provided description (if any) for the snapshot.
description="---"

printHelp() {
    echo "Usage: snap [OPTION]"
    echo "Create a snapshot of the whole system (snapshots of all subvolumes in the system)."
    echo
    echo "Mandatory arguments to long options are mandatory for short options too."
    echo "  -d, --description=DESC     add a description DESC to the file created with"
    echo "                             the snapshot explaining about the snapshot"
    echo "      --help     display this help and exit"
    echo "      --version  output version information and exit"
}

printVersion() {
    echo "snap 0.1"
    echo "License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>."
    echo "This is free software: You are free to change and redistribute it."
    echo "There is NO WARRANTY, to the extent permitted by law."
    echo
    echo "Written by Mubeen Iqbal."
}

printInvalidOptionError() {
    echo "snap: invalid option -- '$(echo "${1}" | tr -d -)'"
    echo "Try 'snap --help' for more information."
}

printNoDescriptionProvidedError() {
    echo "snap: No description provided"
}

validate() {
    # If any of the options is one of the following then execute and exit.
    for param; do
        case "${param}" in
            --help)
                printHelp
                exit 0
                ;;
            --version)
                printVersion
                exit 0
                ;;
        esac
    done
    
    # Handle other options.
    while [ "${1}" != "" ]; do
        case "${1}" in
            -d | --description)
                shift
                
                if [ -z "${1}" ]; then
                    printNoDescriptionProvidedError
                    exit 2
                else
                    description="${1}"
                fi
                ;;
            *)
                printInvalidOptionError "${1}"
                exit 2
                ;;
        esac
        
        shift
    done
}

printSnapshotPaths() {
    echo -e "<mount point>\t<source subvolume>\t\t\t<snapshot path>"
    
    for (( i=0; i<"${totalSubvolumes}"; ++i )) {
        printf "%s\t\t%s\t%s\n" "${mountPoints[i]}" "${sourceSubvolumes[i]}" "${snapshotDir}"/"${dateTime}"/"${snapshotNames[i]}"
    }
}

createSnapshot() {
    for (( i=0; i<"${totalSubvolumes}"; ++i )) {
        sudo btrfs subvolume snapshot -r "${sourceSubvolumes[i]}" "${snapshotDir}"/"${dateTime}"/"${snapshotNames[i]}"
    }
}

printSnapshotCommands() {
    for (( i=0; i<"${totalSubvolumes}"; ++i )) {
        printf "btrfs subvolume snapshot -r %s %s\n" "${sourceSubvolumes[i]}" "${snapshotDir}"/"${dateTime}"/"${snapshotNames[i]}"
    }
}

createReadmeFile() {
    sudo printf "%s\n" "$(
    echo -e "This file has been created automatically by snap.\n"
    echo -e "Snapshot created on: $(date)"
    echo -e "Author (user): "$(whoami)""
    echo -e "Readonly snapshot: yes\n"
    echo -e "<snapshot commands>"
    
    printSnapshotCommands
    echo
    printSnapshotPaths
    
    echo -e "\nDescription"
    echo -e "===========\n"
    echo "${description}"
    )" > "${readmeFilePath}"
    
    echo "A readme file for the snapshot has been created at:"
    echo "${readmeFilePath}"
}



#
# Main
#

# Validate if this utility is being used with the proper syntax.
validate "${@}"

sudo mkdir ""${snapshotDir}"/"${dateTime}""

echo -e "Creating a full system snapshot on "${d}" (yyyy-mm-dd) at "$(echo "${t}" | tr - :)" (hh:mm:ss).\n"

createSnapshot

echo -e "A full system snapshot has been created at:"
echo -e ""${snapshotDir}"/"${dateTime}"/\n"

printSnapshotPaths
echo
createReadmeFile