CoreOS notes

coreos-notes.md

CoreOS notes

• fleet has been deprecated https://coreos.com/blog/migrating-from-fleet-to-kubernetes.html

• Cloud init has been deprecated https://coreos.com/os/docs/latest/provisioning.html#using-container-linux-configs

• Default time zone is UTC, recommended to avoid confusion between different zones https://coreos.com/os/docs/latest/configuring-date-and-timezone.html

• Container Linux Config specification https://coreos.com/os/docs/latest/configuration.html

• etcd runs locally but the idea is to be run in only once machine under a CoreOS cluster https://coreos.com/os/docs/latest/cluster-architectures.html#easy-developmenttesting-cluster

• Adding maintance window for auto-updates https://coreos.com/os/docs/latest/update-strategies.html#auto-updates-with-a-maintenance-window

• Adding Docker registry auth at instance creation https://coreos.com/os/docs/latest/registry-authentication.html#copying-the-config-file-with-a-container-linux-config

• Adding swap at instance creation https://coreos.com/os/docs/latest/adding-swap.html#adding-swap-with-a-container-linux-config

• Systemd timers are the replacement for crontab https://coreos.com/os/docs/latest/scheduling-tasks-with-systemd-timers.html

• Auto-update by lock to prevent losing quorum in a clusrer https://coreos.com/os/docs/latest/update-strategies.html#etcd-lock

• If a Systemd service is edited after being activated, the daemon have to be reloaded with systemctl daemon-reload https://www.freedesktop.org/software/systemd/man/systemctl.html#daemon-reload. Might be also needed systemctl restart <SERVICE_NAME>

• Run manual update update_engine_client -check_for_update https://coreos.com/os/docs/latest/update-strategies.html#manually-triggering-an-update

• Reset failed Systemd services use systemctl reset-failed

• List all the scheduled tasks systemctl list-timers --all

• Check system logs (by newest to older) journalctl -r

• Check CoreOS version cat /etc/os-release

• Check Docker daemon log journalctl -f -u docker