Matrix Synapse

Certificates

Renew Let's Encrypt TLS certificate without stopping nginx

certbot renew --webroot -w /path/to/webroot

Where /path/to/webroot is the same path that nginx serves the site on port 80, often /var/www or /srv/www.
See nginx config, it should be under something like

location / {
	root /srv/www;
}

PostgreSQL

List databases

psql --u admin_user --list

Vacuum (clean up) a database

vacuumdb --u admin_user db_name

Compressing Synapse database

Media

Delete media older than X days

This might delete avatars and other old files that are actively used.

find /var/lib/matrix-synapse/media/ -mtime +365 -delete