Add base files

.gitignore

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+env
+exclude

README.md

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+# borg-remote-android
+A utility for easy android backups using rsync (locally) and borg (on a remote).
+
+## Motivation
+I was having trouble installing borg (even though there was [borgbackup_on_android](https://github.com/ravenschade/borgbackup_on_android)) and running borg was slow since I was using lzma compression.
+
+I created this tool so that the copy to the server could be quick, then the server could perform the heavy lifting of encryption/compression. This also allows for less required time on WiFi, since the only network-intensive operations are on the resumable rsync transfer.
+
+## Usage
+In Termux, run:
+```bash
+./backup-android.sh
+```
+
+and it will notify you when complete.
+
+Alternatively, you can add a Termux widget to your home screen (`./setup.sh` auto-installs in the `.shortcuts` directory), so backups can be made with a single tap from the home screen.
+
+## Installation
+Quick, 4 line installation:
+```bash
+apt update
+apt install -y git rsync openssh
+git clone https://gitea.austenwares.com/stonewareslord/borg-remote-android
+env bash borg-remote-android/setup.sh
+```
+
+Same installation as a one-liner
+```bash
+apt update && apt install -y git rsync openssh && git clone https://gitea.austenwares.com/stonewareslord/borg-remote-android && env bash borg-remote-android/setup.sh
+```
+
+## Updating
+The entire config is stored in `env`, which is in `.gitignore`, so running a simple `git pull` will update without losing custom changes.

backup-android.sh

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+#!/data/data/com.termux/files/usr/bin/bash
+# Initialize
+ABSPATH="$(readlink -f "$BASH_SOURCE")"
+cd "${ABSPATH%/*}" || { echo "Cannot change directory" >&2; exit 1; }
+test -f ./env && source ./env || { echo "Unable to source user variables in $PWD"; exit 1;  }
+
+# From https://serverfault.com/a/799198
+# Since Termux has no uuidgen command, we need to create one randomly
+function uuidgen() {
+  od -x /dev/urandom | head -1 | awk '{OFS="-"; print $2$3,$4,$5,$6,$7$8$9}'
+}
+
+# From https://unix.stackexchange.com/a/27014
+function time_diff {
+  # Find the time difference between the two arguments (in seconds)
+  local T="$(( "$1" - "$2" ))"
+  local D=$((T/60/60/24))
+  local H=$((T/60/60%24))
+  local M=$((T/60%60))
+  local S=$((T%60))
+  (( $D > 0 )) && printf '%dd ' $D
+  (( $H > 0 )) && printf '%dh ' $H
+  (( $M > 0 )) && printf '%dm ' $M
+  (( $D > 0 || $H > 0 || $M > 0 )) && printf 'and '
+  printf '%ds\n' $S
+}
+
+function backup() {
+  # First, we need to rsync our changes to the host
+  echo "Running rsync..."
+  $RSYNC_COMMAND "$SOURCE_LOCATION" "$REMOTE_HOST:$DESTINATION_LOCATION" || return 1
+
+  # Next, instruct the host to create a borg
+  echo "Running borg..."
+  ./run_remote.sh nohup sh -c "cd \"$DESTINATION_LOCATION\"; $BORG_COMMAND \"$BORG_REPO::$HOSTNAME-$(uuidgen)\" \"$DESTINATION_LOCATION\"" || return 2
+}
+
+# Take wakelock so we don't fall asleep
+termux-wake-lock
+START_TIME="$(date +%s)"
+
+# Perform the backup
+backup
+RESULT=$?
+DURATION="$(time_diff "$(date +%s)" "$START_TIME" )"
+
+echo "Completed $(date +%F-%T)"
+echo "Duration: $DURATION"
+
+if (( RESULT == 0 )); then
+  termux-notification --title "Backup completed successfully in $DURATION"
+else
+  termux-notification --title "Backup failed in $DURATION"
+fi
+
+# Remove our wakelock
+termux-wake-unlock

doc/state-diagram.txt

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+@startuml
+Android -> Android: Take wakelock
+
+note right of rsync
+  The borg and rsync servers can be the server.
+  ""BORG_REPO"" and ""REMOTE_HOST"" are configurable.
+end note
+
+Android -> "Rsync Server" as rsync: rsync data to temporary location
+rsync --> Android: rsync complete
+Android -> rsync: nohup spawn borg backup
+
+rsync -> "Borg Server" as borg: borg backup temporary directory
+borg --> rsync: borg complete
+rsync --> Android: borg complete
+
+Android -> Android: Show success notification
+Android -> Android: Release wakelock
+@enduml

run_remote.sh

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+#!/data/data/com.termux/files/usr/bin/bash
+ABSPATH="$(readlink -f "$BASH_SOURCE")"
+cd "${ABSPATH%/*}" || { echo "Cannot change directory" >&2; exit 1; }
+test -f ./env && source ./env || { echo "Unable to source user variables"; exit 1;  }
+ssh "$REMOTE_HOST" -- "$@"

setup.sh

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+#!/data/data/com.termux/files/usr/bin/bash
+ABSPATH="$(readlink -f "$BASH_SOURCE")"
+cd "${ABSPATH%/*}" || { echo "Cannot change directory" >&2; exit 1; }
+
+function ask() {
+  echo  -n "$1 [Y/n]? "
+  read RESP
+  if [ -z "$RESP" ] || [ "${RESP,,}" = "y" ]; then
+    return 0
+  fi
+  return 1
+}
+
+# Read a variable 
+function configure_var() {
+  # If the variable already exists, continue without asking questions
+  if [ ! -z "${!1}" ]; then
+    echo "It is ${!1}"
+    return
+  fi
+
+  DEFAULT="$2"
+  echo -n "export $1= ($2): "
+  read RESP
+  RESP="${RESP:-$DEFAULT}"
+  # Save the variable
+  #TODO: This introduces possible bugs when quotes are involved with RESP
+  echo "# Line added on $(date +%F-%T)" >>env
+  echo "export $1=\"$RESP\"" >>env
+  # Load the variable for use in this script
+  export "$1"="$RESP"
+}
+
+# Begin configuration
+echo
+echo "Asking config questions..."
+echo "IMPORTANT: Trailing slashes matter for paths. Consult the rsync manual for details."
+echo "It is recommended to use trailing slashes for all _LOCATION variables."
+echo "Also, paths can be relative or absolute"
+echo
+
+# Load existing configurations
+test -f ./env && source ./env
+
+configure_var LOCAL_HOSTNAME android1
+configure_var REMOTE_HOST user@example.com
+configure_var SOURCE_LOCATION "/storage/emulated/0/"
+configure_var DESTINATION_LOCATION "tmp/borg/$LOCAL_HOSTNAME/"
+configure_var BORG_REPO "ssh://$REMOTE_HOST/~/borg-backups"
+configure_var BORG_COMMAND "borg create --verbose --progress --stats --one-file-system --exclude-caches --compression=auto,lzma --exclude=storage/emulated/0/Android"
+configure_var RSYNC_COMMAND "rsync --relative --recursive --links --times --human-readable --partial --info=progress2 --delete --delete-excluded --exclude=storage/emulated/0/Android"
+
+# Install borg-backup into ~/.shortcuts
+mkdir -p ~/.shortcuts
+if [ -L ~/.shortcuts/borg-backup ]; then
+  rm ~/.shortcuts/borg-backup
+fi
+ln -s "$(readlink -f backup-android.sh)" ~/.shortcuts/borg-backup || echo "Unable to link to ~/.shortcuts" >&2
+
+# Ask about authentication
+SSH_KEYGEN_COMMAND="ssh-keygen -b 512 -t ed25519 -f $HOME/.ssh/id_ed25519 -N ''"
+ask "Generate a new ssh key ($SSH_KEYGEN_COMMAND)" && $SSH_KEYGEN_COMMAND
+ask "Run ssh-copy-id on host" && ssh-copy-id "$HOST"
+
+# Create destination location
+echo "Creating DESTINATION_LOCATION"
+./run_remote.sh mkdir -p "$DESTINATION_LOCATION"
+
+# Exclude file
+touch exclude
+ask "Edit exclude file with vi" && vi exclude
+
+# Run final checks
+ask "Check if borg command exists (on remote)" && { ./run_remote.sh command -v borg || echo "Borg command not found on remote host"; }
+ask "Run borg list (on remote)" && ./run_remote.sh borg list "$BORG_REPO"