Simple shell script to backup to Amazon over iSCSI

Question

The script works but I know that it can be improved. Please note that my scripting skills are very basic :) (as it can be seen in my Frankenstein script – I took bits and pieces of the code from different tutorials).

I would appreciated if someone could review this script and identify some major flaws.

Some other questions that I have:

1. After the backup is complete is it necessary/better to logout from the amazon and unmount the volume?
2. Is it better to check if the volume is mounted based on the UUID?

#!/bin/bash
##
## VARIABLES
##
BACKUP_FROM="/folder/"
BACKUP_TO="/folder/"
LOG_FILE="/var/log/backup.log"
SCSI="/sbin/iscsiadm"
VOL="ghrryhfd-56655565-456456-3453-dfhthjtrrgg"
##
## SCRIPT
##
# Check that the log file exists
if [ ! -e "$LOG_FILE" ]; then
    touch "$LOG_FILE"
fi

# Check if the volume is mounted if not login to amazon and mount
if mountpoint -q /mount_folder; then
echo "$(date "+%Y-%m-%d %k:%M:%S") - Volume mounted" >> "$LOG_FILE"
else
echo "$(date "+%Y-%m-%d %k:%M:%S") - Mounting!" >> "$LOG_FILE"
$SCSI --mode node --targetname abc.222-99.com.amazon:volume_name --portal 1.1.1.1:9999 --login
sleep 10
mount -U "$VOL" /mount_folder
sleep 8
fi

# Start entry in the log
echo "$(date "+%Y-%m-%d %k:%M:%S") - Sync started." >> "$LOG_FILE"

# Start sync
if rsync -a -v "$BACKUP_FROM" "$BACKUP_TO" &>> "$LOG_FILE"; then
    echo "$(date "+%Y-%m-%d %k:%M:%S") - Sync completed succesfully." >> "$LOG_FILE"
else
    echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: rsync-command failed." >> "$LOG_FILE"
    echo "$(date "+%Y-%m-%d %k:%M:%S") - ERROR: Unable to sync." >> "$LOG_FILE"
    echo "" >> "$LOG_FILE"
    exit 1
fi

# End entry in the log
echo "" >> "$LOG_FILE"
exit 0

Answer 1

Extract common logic to a helper function

Notice the similarity in these statements:

echo "$(date "+%Y-%m-%d %k:%M:%S") - Volume mounted" >> "$LOG_FILE"
...
echo "$(date "+%Y-%m-%d %k:%M:%S") - Mounting!" >> "$LOG_FILE"
...
echo "$(date "+%Y-%m-%d %k:%M:%S") - Sync started." >> "$LOG_FILE"

They all have the same pattern:

echo "$(date "+%Y-%m-%d %k:%M:%S") - MESSAGE" >> "$LOG_FILE"

So it's a good candidate to turn into a function:

log() {
    echo "$(date "+%Y-%m-%d %k:%M:%S") - $@" >> "$LOG_FILE"
}

So that you can simplify the uses like this:

log "Volume mounted"
...
log "Mounting!"
...
log "Sync started."

Result of mount

The mount command might fail. When that happens, you might want to abort:

if ! mount -U "$VOL" /mount_folder; then
    log "Unable to Mount"
    exit 1
fi

Pointless touch

This code is completely unnecessary. Whether the file existed or not, whether you touch it or not, it won't affect the rest of the script. You can safely remove it.

if [ ! -e "$LOG_FILE" ]; then
    touch "$LOG_FILE"
fi

Simplify

This is kind of tedious:

echo "" >> "$LOG_FILE"

You can just drop the "" to simplify:

echo >> "$LOG_FILE"

And, you don't need exit 0 at the end of the script.