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Command-line guides for developers who run their own servers: Ubuntu and Debian administration, SSH, mail, MySQL backups, Webmin and hardening, including how to run AI agents and local models safely.
A patched Ubuntu server can still print PHP 8.3.6, and an update does nothing until PHP restarts. Four checks that the 21 October PHP fixes landed on your WordPress or Magento server.
In the example worked through here, the weights are the small object. Context length multiplied by concurrency decides the hardware, and the driver stack decides whether it stays working.
Learn how to give AI agents useful Linux tools without turning prompt injection into root access, using dedicated identities, typed brokers, sandboxing and independent audit evidence.
How to extract a .gz or .tar.gz file on Windows, macOS and Linux, keep the original, read it without extracting, and fix “not in gzip format”.
One tested mysqldump command for InnoDB, a login that keeps the password off the command line, gzip, a restore check, and the errors that still exit with status 0.
Tick File Manager for a Webmin user, then limit its folders and Unix user. In a Webmin 2.670 test, a plain tick gave root access to the whole disk.
On a server running Virtualmin, run the list-domains command with –name-only as root and it prints every hosted domain, aliases included; the –alias option does the opposite and keeps only aliases.
Stop re-entering your SSH key passphrase after a Mac restart. Add UseKeychain and AddKeysToAgent to ~/.ssh/config and check it with ssh-add -l.
Start, stop, restart or reload Postfix on Ubuntu with systemctl, check that it is really running and deal with a full mail queue.
Webmin File Manager shows a folder’s own entry size rather than its total. How to see the real total with the spacebar or Properties, and when du in Command Shell is the better check.
In Terminal, run ssh user@server, check the host fingerprint before you type yes, then log in. A key and a ~/.ssh/config name make later logins one word.
