1) Customize /etc/aide.conf to your liking. In particular, add
   important directories and files which you would like to be
   covered by integrity checks. Avoid files which are expected
   to change frequently or which don't affect the safety of your
   system.

2) Run "/usr/sbin/aide --init" to build the initial database.
   With the default setup, that creates /var/lib/aide/aide.db.new.gz

3) Store /etc/aide.conf, /usr/sbin/aide and /var/lib/aide/aide.db.new.gz
   in a secure location, e.g. on separate read-only media (such as
   CD-ROM). Alternatively, keep MD5 fingerprints or GPG signatures
   of those files in a secure location, so you have means to verify
   that nobody modified those files.

4) Copy /var/lib/aide/aide.db.new.gz to /var/lib/aide/aide.db.gz
   which is the location of the input database.

5) Run "/usr/sbin/aide --check" to check your system for inconsistencies
   compared with the AIDE database. Prior to running a check manually,
   ensure that the AIDE binary and database have not been modified
   without your knowledge.

6) To schedule daily integrity checks, enable the systemd timer:

   systemctl enable --now aide-check.timer

   View results with: journalctl -u aide-check
   Check timer status with: systemctl status aide-check.timer

   The timer runs daily with low CPU/IO priority to minimize impact
   on production workloads. It is disabled by default — only enable
   it after initializing the database (steps 2-4).

   Caution!

   It cannot be guaranteed that the AIDE binaries, config file and
   database are intact. It is not recommended that you run automated
   AIDE checks without verifying AIDE yourself frequently. In addition
   to that, AIDE does not implement any password or encryption
   protection for its own files.

   It is up to you how to put a file integrity checker to good effect.
   On a compromised system, the intruder could disable the automated
   check. Or he could replace the AIDE binary, config file and database
   easily when they are not located on read-only media.