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Ntfy is a simple notification service that allows sending notifications via a simple HTTP request.

Sending notifications is done by making a request to a unique URL that represents a topical namespace. Here’s a simple example from the ntfy.sh homepage:

curl -d "Backup successful 😀" ntfy.sh/mytopic 

The ntfy.sh website mentions that the topic name is essentially a password, so it’s important to pick a name that’s not easily guessed.

I usually use a short name (e.g. notifications) followed by a unique UUIDv4 string, which results in a topic name that looks like this:

ntfy.sh/notifications-8b8d0ca2-3e9d-444a-8169-480042125f6a

Since the app will truncate the string, the extra length that’s appended doesn’t affect readability in the least.

SSH Notifications

To enable notifications for SSH logins, the system-wide profile will need to be edited:

sudo nano /etc/profile

And the following snippet added to the end of the file:

if [ -n "$SSH_CLIENT" ]; then

NTFY="${USER}@$(hostname -f) from $(echo $SSH_CLIENT|awk '{print $1}')"

curl -s -H "Title: SSH Login" -d "$NTFY" ntfy.sh/notifications-8b8d0ca2-3e9d-444a-8169-480042125f6a > /dev/null

fi

Where notifications-8b8d0ca2-3e9d-444a-8169-480042125f6a is the Ntfy topic.

I found the awk logic from a blog post on email alerts for SSH logins, which I repurposed for use with Ntfy.

One additional change I made from the original code snippet was sending the output to /dev/null which prevents users from seeing the verbose output when they themselves login.

Below is an example of how a login notification looks in the Ntfy app:

This type of system requires less moving parts than using sendmail for example, and push notifications are practically instant.

Links

• ntfy - ntfy.sh