Guides

Watch a Linux server

Your Mac signs in over SSH with its own key, runs a short read-only script and reads disk, memory, load, services, containers, ports, updates and the files you choose. Nothing is installed on the server.

What it checks

Health

Disk space and inodes (warning at 80%, critical at 90% by default), available memory (under 10% is degraded, under 5% a problem), load per CPU (over 2 degraded, over 4 a problem), uptime and the busiest processes.

Services and containers

The systemd services you list must be active, failed units are reported, and the Docker containers you list must be running and healthy.

Ports and files

The ports you list must be listening. Watched files and folders are fingerprinted: a change or a missing file is a problem until you accept it.

Updates and clock

Pending security updates (Debian, Ubuntu, Fedora, RHEL), a reboot required by an update, and clock drift of 5 seconds or more.

What each status means

UpConnected, and every value is within its limits.
Slow or degradedDisk past the warning level, low memory, high load, security updates or a reboot pending, a container starting, or SSH slower than 5 seconds.
DownNo connection, a service or container stopped, a port not listening, disk past the critical level, changed files, or a server key that changed. A failed connection is retried once after 3 seconds.

Add one, step by step

1
Copy your Mac’s key
In the Mac app, open Settings, Servers. Monitorizer made its own key (Ed25519). Click “Copy the command that adds it”. You can also choose “My existing key” to import yours.
2
Add it on the server, once
Sign in to the server as the user Monitorizer will use and run the copied command. It adds the key to ~/.ssh/authorized_keys:
```
mkdir -p ~/.ssh && chmod 700 ~/.ssh && echo 'ssh-ed25519 AAAA… monitorizer@your-mac' >> ~/.ssh/authorized_keys && chmod 600 ~/.ssh/authorized_keys
```
3
Add the monitor
On the Mac, paste user@host (for example ubuntu@203.0.113.10) in New Monitor. On the website, choose Server and fill in host, port and user. List the services, containers, ports and files to watch.
4
Trust the server’s key
On the first check the monitor waits with “Server key not confirmed yet”. Open it in the Mac app, compare the fingerprint with the server’s, then click “Trust this key”:
```
ssh-keygen -lf /etc/ssh/ssh_host_ed25519_key.pub
```

Every setting

The same settings appear in the Mac app and on the website. You can change them later, from either side.

Host: Name or IP address of the server.
Port: The SSH port, 22 by default.
User: The account to sign in with. root is not required: with a normal user, everything is read except what needs root, and sudo is used only if it works without a password.
Services: One per line, as systemctl names them: nginx, mysql, docker.
Docker containers: One container name per line.
Ports that must listen: One per line, for example 443 or 3306.
Watched files: One path per line, such as /etc/passwd or /var/www/html. Folders are read up to 3 levels and 2000 files.
Disk warning at / Disk critical at (%): 80 and 90 by default.
Check: 5 minutes by default.

Tips

Create a dedicated user for Monitorizer: it only needs to sign in and read.
Watch /etc/passwd, /etc/ssh/sshd_config and your web root to know when something changes that you did not change.
The script is plain sh for Linux. On a Mac or BSD server some values look wrong.
If the server’s key changes (reinstall, new server), the monitor stops and waits for “Trust the new key”: it never accepts a new key silently.

Questions

Is it safe?

The key stays on your Mac and never syncs. The script only reads, travels encoded, and service names are checked before use. Every server key is confirmed by you.

Can I use a password?

No, keys only. Import your own key (Ed25519 or RSA, with a passphrase) in Settings, Servers if you do not want to add a new one.

Where are the commands that Monitorizer runs?

On the home page, under the server section: every command is listed. They only read.

Add a server monitor

Your Mac starts checking it within minutes. You can change every setting later.

Add it now