SlackBuildsOrg/system/tuptime

tuptime is a daemon-less uptime statistics collection tool.

It lets you know how long your machine manages to run without a reboot,
and shows whether the reboot was graceful or hard.

The slackbuild installs a SystemV-style initscript into rc3.d and rc4.d.
The time your machine spends in other runlevels is not counter, because,
presumably, it cannot be considered fully up.

The slackbuild also installs a speically crafter crontab for the
_tuptime user, to periodically log machine state.

The scripts expects to have a system user called _tuptime. Create one
by running:

groupadd -g 379 _tuptime
useradd -u 379 -g 379 -d /var/lib/_tuptime _tuptime