Managing System Time - Paiet/Tech-Journal-for-Everything GitHub Wiki

  • Time is used for many things
    • Your calendar and clock
    • Scheduling tasks (cron)
    • Logging and auditing
    • Security protocols like IPSec
  • Accurate time
    • Can be manually set
    • Can be imported from the hardware clock
    • Can be imported from an NTP server
  • Start with the timezone
  • Configuring a timezone without systemd
    • Before systemd it was all over the place2
    • Places to check:
      • /etc/timezone
      • /etc/localtime
      • /usr/share/zoneinfo
      • tzselect
      • tzconfig
      • $TZ
    • In RedHat/CentOS use:
      • ln -sf /usr/share/zoneinfo/America/New_York /etc/localtime
    • In Ubuntu:
      • vi /etc/timezone
        • America/New_York
  • Configuring a timezone with systemd
    • timedatectl
    • timedatectl list-timezones
    • timedatectl list-timezones | grep America
    • sudo timedatectl set-timezone America/New_York
  • Setting the time
    • timedatectl set-time "yyyy-MM-dd hh:mm:ss"
  • Configuring the hardware clock
    • date
    • hwclock -r
    • date -s "1 JUN 2021 12:00:00"
    • hwclock --systohc (or -w)
    • hwclock --hctosys (or -s)