Copy backups to another server with rsync and cron

[Bathinda (Bathinda Helper)]

@johncs

#!/usr/bin/env bash

set -xe

HOST="$1"
DIR="$2"
if [ -z "$HOST" ] || [ ! -d "$DIR" ]; then
	echo "$0 HOST DIR"
	exit 1
fi

# --ignore-existing will have rsync ignore any backups that have already been
# copied.
# --delay-updates ensures that only complete backups ever make it into $DIR. If
# this isn't specified, partial backups could end up in $DIR, and because
# --ignore-existing won't perform any kind of equality check, the problem will
# not be corrected or detected.
rsync --ignore-existing --delay-updates "$HOST:/var/discourse/shared/standalone/backups/default/*" "$DIR"

For anyone coming to this thread like I did, I’d like to explain this first post in the topic a bit further.

• This is a bash script, which may be pasted ‘as-it-is’ in a file named anything, but having extension .sh
• First line of the script just sets the environment for the script to run, as to which shell or environ should be used: #!/usr/bin/env bash): This tells the system to use the bash interpreter found via the env command.
• flags (set -xe):
  • -x: Enables debugging, which means that each command and its arguments will be printed to the terminal before being executed. This is helpful for debugging the script.
  • -e: Causes the script to exit immediately if any command returns a non-zero status (indicating an error). This is useful for preventing the script from continuing after a failure.
• And in next imp step, Variables (HOST="$1" DIR="$2"):
  • HOST="$1": Assigns the first argument passed to the script ($1) to the variable HOST. That is when this script is run, it’d demand some input from the user, and whatever first input ($1) will be entered by the user, that will be passed/considered as the ‘Host’ value (from where data perhaps will be copied from).
  • DIR="$2": Assigns the second argument passed to the script ($2) to the variable DIR. I.e. whatever (directory path) will be entered by the user after inputting 1st value, (called ‘$2’) will be taken by the script as ‘Dir- target directory’.
    If anyone interested I can explain the remaining 2 steps also, but suffice is to say that next step just checks that user supplies the correct host and target directory values when prompted. Otherwise (last step) would return 1 as an error output.

The main thing I’d reiterate that this is a script, which when run, would demand user for the host (from where data is to be copied) and target directory (where data is to be pasted). And you’d include the path to this file in your cron job file, which might run this script file as many times in the day as you would set in the cron file.

But what I’ve failed to understand is that where are actual copy pasting (or backup) commands?
How would actual Sync occur?