Merge pull request #4 from kubrickfr/check_dependencies

Check if all required binaries exists before doing anything else

README.md

@@ -18,6 +18,15 @@ Rather than dealing with the complexity of custom file formats and metadata file
 
 As such if you want to change the format (compression, encryption, file container, etc.), please start a new backup _epoch_ so as not to mix the two.
 
+# Return value
+
+It is important that you check the return value of the back-up script for proper monitoring and alerting.
+
+* 0: everything went fine
+* 1: a "usage" error occured. You used a unrecognised command switch, or referenced a volume or snapshot that does not exist
+* 2: an error occurred after the snapshot was created, **you should pay close attention to these**! The script will have tried to delete the newly created snapshot so that subsequent incremental backups can be made from the last good known state
+* 3: a required dependency is not installed
+
 # Important security recommendations
 This is all rather common sense, but:
 

check_deps.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+
+if ! command -v age &> /dev/null; then
+  echo "command not found: age"
+  exit 3
+fi
+if ! command -v aws &> /dev/null; then
+  echo "command not found: aws"
+  exit 3
+fi
+if ! command -v lz4 &> /dev/null; then
+  echo "command not found: lz4"
+  exit 3
+fi
+if ! command -v mbuffer &> /dev/null; then
+  echo "command not found: mbuffer"
+  exit 3
+fi
+if ! command -v split &> /dev/null; then
+  echo "command not found: split"
+  exit 3
+fi
+if ! command -v sed &> /dev/null; then
+  echo "command not found: sed"
+  exit 3
+fi
+if ! command -v btrfs &> /dev/null; then
+  echo "command not found: btrfs"
+  exit 3
+fi

restore_backup.sh

@@ -2,9 +2,11 @@
 #
 if [ "$EUID" -ne 0 ]
   then echo "Please run as root"
-  exit
+  exit 1
 fi
 
+$(dirname "$0")/check_deps.sh || exit 3
+
 DELETE_PREVIOUS=false
 
 OPTSTRING="b:p:e:i:s:d"

stream_backup.sh

@@ -2,9 +2,11 @@
 #
 if [ "$EUID" -ne 0 ]
   then echo "Please run as root"
-  exit
+  exit 1
 fi
 
+$(dirname "$0")/check_deps.sh || exit 3
+
 DELETE_PREVIOUS=false
 CHUNK_SIZE="512M"
 SOURCE_EPOCH=""
@@ -91,7 +93,7 @@ function cleanup () {
   exit 2
 }
 
-aws s3 ls s3://${BUCKET}/${PREFIX} >> /dev/null \
+aws s3 ls s3://${BUCKET}/${PREFIX} >/dev/null 2>&1 \
   && echo "SECURITY WARNING: current AWS IAM entity is allowed to list bucket contents! This can allow an attacker using the same identity to overwrite files and ruin your backups!" >&2
 
 SEQ=$(date +%s)