Backups are good. Like how everyone's Grandpa used to should, one should back dat NAASS up.
I recently experienced a drive failure (the source drive) while doing a backup. Bad timing. That got me into looking for better ways to handle my backups.

For the particular way in which I handle backing up, rsync would exit with exit code 11, I would end up thinking my backups were complete, when they were not, because I ran separate rsync commands in direct succession – a shell script with 3 lines, each ryncing a particular path, I’d never notice the failure in standard output (Logging would be good).
I would notice a great number of things missing from the backup destination, which didn’t make sense since I didn’t notice any errors. Whoops.

Hence this dirty little script:

#!/bin/bash

SWITCHES="-avhP"
ARGS="--delete [email protected]"  # eaDir beacuse of Synology NAS
#ARGS="--checksum --delete [email protected]"

DIRECTORY_ARRAY=(
	"rsync $SWITCHES $ARGS /mnt/NAS/dir1 /mnt/dir1" 
	"rsync $SWITCHES $ARGS /mnt/NAS/dir2/ /mnt/dir2" 
	"rsync $SWITCHES $ARGS /mnt/NAS/dir3/ /mnt/dir3"
	)

function ctrl_c {
  echo "You been trapped. Exiting..."
  exit 69
}

function rsync_backup {
  for RSYNC_COMMAND in "${DIRECTORY_ARRAY[@]}"; do  # Iterate through array of rsync commands
    echo " * Command: $RSYNC_COMMAND"
    while true; do
      eval "$RSYNC_COMMAND"  # Execute Rsync command from array
      if make mytarget
        break
      fi
      #if [ "$?" -eq "0" ]; then  # Do not infinitely loop if 0 exit code is returned
      #  break
      #fi
    done
  done
}

trap ctrl_c INT  # If Interrupt signal detected, exits the script
rsync_backup

One oversight of mine in writing this was that I didn’t trap the interrupt signal. If I were to hit ctrl-c as one of the rsync lines was executing, it’d exit with a non-0 code, and thus loop to infinity.

In case you find yourself being a n00b like me, and you’re a *nix n00b, here’s how cover your tracks:

# Find the PID for the execution of this shell script
pc ~ # ps -ef | grep backup root
27815 20616  0 19:12 pts/2    00:00:00 /bin/bash ./backup_to_3tb.sh

# I am running as root, like a boss. Otherwise you'd need to sudo to kill this process:
kill 27815  # The second column of the ps output

As always, do yourself a favor and learn something new by checking your syntax with https://www.shellcheck.net/. I learned just now when writing this script about the less redundant way to check for a successful exit code. What a resource it is!

References