Simple automated email alerts

You have a remote system which you want to know the state of. Or you want to monitor it. Or you want to be notified when something happens. But of course you don't want to constantly log into the system and check. There can be dozens parameters to check. You might forget one or two. And that is not a true zen if you have to do this manually.

So, here comes mailing notifications. That'd be awesome to get an email once a situation has occurred. But we don't want to spend time and money on a SMTP server. And we just want to monitor our home server. The solution is easy - use any of your GMail accounts (it can be any provider, but I'm here talking about GMail) or register a new one.

Then write a script. Copy paste from here and edit.

alert.sh

1. #!/bin/sh
3. source "${LOCAL_CONFIG_DIR}/mailx.config.sh"
5. SUBJECT="Alert! Raspberry Pi Home. rootfs > ${2}%"
6. TEXT="Alert on Raspberry Pi home. In the last ${1} seconds rootfs passed the threshold of ${2} and reached ${3}%."
8. echo ${TEXT} | \
9. env MAILRC=/dev/null from="${SENDER}" smtp-auth-user="${SENDER}" smtp-auth-password="${SENDER_PASSWORD}" \
10. mailx -n \
11.     -S smtp-use-starttls \
12.     -S smtp-auth=login \
13.     -S smtp="$SMTP_SERVER" \
14.     -s "${SUBJECT}" "${RECEIVER}"

and here is a mailx.config.sh which is included at line #3

1. RECEIVER=yourself@gmail.com
2. SENDER=alert...@gmail.com
3. SENDER_PASSWORD="alert...@gmail.com password"
4. SMTP_SERVER=smtp://smtp.gmail.com:587

I separated config from the alert script because you can have a number of alerts which you want to use the same config with.

This is the simplest automated notification functionality. It sends a notification in plain text. There are ways to attach files (read man mailx) and there are ways to include html as a body. For my purposes it was perfectly fine, so I didn't bother myself with decorations.


UPDATE [September 30, 2013]

Multiline emails can be sent using this technique:

1. (
2. cat << EOF
3. Message from hostname '$HOSTNAME'.
4.  
5. This system is reaching/exceeding the defined threshold value ($ALERT_THRESHOLD) during the last '$ALERT_TIMEINTVL' seconds.
6.  
7. The current value is: $current_value
8.  
9. Please take proper actions to correct this situation.
10. EOF
11. ) | \
12. env MAILRC=/dev/null from="${SENDER}" smtp-auth-user="${SENDER}" smtp-auth-password="${SENDER_PASSWORD}" \
13. mailx -n \
14.     -S smtp-use-starttls \
15.     -S smtp-auth=login \
16.     -S smtp="$SMTP_SERVER" \
17.     -s "${SUBJECT}" "${RECEIVER}"