Ubuntu

https://www.digitalocean.com/community/tutorials/how-to-view-and-configure-linux-logs-on-ubuntu-and-centos
https://dzone.com/articles/what-are-linux-logs-how-to-view-them-most-importan
https://www.commandlinefu.com/commands/browse/25/50/75/100/125/150
https://tproger.ru/digest/useful-linux-utilities/

last | grep sysadmin
lastlog
who
lnav /var/log/auth.log
tailf /var/log/syslog | ccze
ccze - Инструмент для декорации логов.