atop.txt

# uh... I know nothing, and here it is!
atop = top + history, and more detail.

It can run interactively like top, but also as a service (atop.service), as which it will sample system load/resources and
  write their values to /var/log/atop/atop_<date>, every $interval seconds (see below), it's some binary format.

Config file sits in /etc/default/atop, unless you run CentOS, then it's /etc/sysconfig/atop. Unless it's simply
  /etc/atoprc, and you can override them in ~/.atoprc, this probably depends on the version. atoprc could be another thing
  altogether which is /supposed/ to have a manpage? I can't find it.

For my current version (2.7.1 CentOS), the config settings are just this:
  LOGOPTS=
  LOGINTERVAL=60
  LOGGENERATIONS=14
  LOGPATH=/var/log/atop

Interval is in seconds, default is 600 for "get and write values every 10 minutes"
Generations is days kept I think (default 28)

Todo:
- useful commandline options
- useful shortcuts in the interface
- graphs based on atop logs