Linux – Perl script that will remotely ssh to linux and get memory status back to the machine

From a high level the basics are security, recovery and security. I say security twice because it encompasses a lot of topics.

Additionally, some of this is context specific.

For example, security contains networking aspects of your machine. Iptables for example. It also encompasses your user administration. Ie. have you disabled root logins?

Security also could technically encompass system maintenance in the sense of are you regularly updating your machine to have the most current patches and fixes. Additionally, have you removed all packages on your system and disabled all services that you are not using and are not required for the server to do its job.

Recovery is more in terms of do you have a backup plan if your server goes down. Your server can go down in two ways broadly speaking. Hardware & software failures. Each are different.

In terms of hardware, are you using raid and also backing up to protect your servers data? Do you have a spare hard drive in case a drive in your raid array goes bad so you can replace it before you lose another? In terms of software, if this is a production server that requires high uptime... are you using a "staging server" to perform updates and "test" things before applying updates/patches to production server.

There is a lot to administration but my thoughts are somewhat biased to web server administration.

Long story short, it is about crossing your t's and dotting your i's.

Anything you do will be insecure without the use of ssh and sshd.

The canonical way is to use scp or even better, rsync and an ssh key without a password.

Alternatively, create a key used only for copy, and on the remote end edit the authorized_keys file to contain only the command(s) you need to run, and the key, e.g.:

# remote_server:/home/copyuser/.ssh/authorized_keys:
command="[...]" ssh-rsa KEY_HERE user@host

There is also scponly available. If you create a user, set their shell in /etc/passwd to /usr/bin/scponly and they will not be allowed to login, but copy files in and out per the normal permissions.