man

What this account is

Owns /var/cache/man, which holds formatted pages and the man database. Under man-db the daily regeneration runs as this user: the man-db systemd service recreates the cache directory if it is missing, removes formatted pages that have not been read in the past week, and then runs mandb to rebuild the index. The login shell is /usr/sbin/nologin, so the account is not interactive. As installed by default neither man nor mandb carries a setuid or setgid bit, and the separation comes from the service running under the account instead. Debian's man-db package does offer the alternative: a configuration question asks whether man and mandb should be installed setuid to this account, so that ordinary users can write cached pages themselves. It defaults to no.

Source: man-db 2.10.2: man-db.service, man-db.timer, file modes on man and mandb, debconf template man-db/install-setuid; base-passwd 3.6.8 (passwd). Read 2026-08-08.

Sources