How often timezone database is updated in EC2 Amazon Linux 2-CodePudding

I have a scheduling use case that deals with end user local time.

I couldn’t find information on how EC2/Amazon Linux 2 updates its timezone database. (Most likely based on IANA one)

Does Amazon Linux 2 guarantee that timezone (TZ) changes (ex: daylight saving changeover dates) are correctly reflected in the running EC2 instances?

For instance:

zdump -v /usr/share/zoneinfo/<Region>/<Timezone> | grep <year>

shows accurate results about timezone changeover dates for my local timezone, but I can't say enough about the others.

Like most other Unix distributions, Amazon Linux 2 likely updates its TZ database regularly from a global authority (such as IANA). But I'm struggling to find this piece of information.

CodePudding user response：

Like most other Linux distributions, Amazon Linux 2 (AL2) distributes time zone data via a package named tzdata that is built specifically for that distribution.

You can search the AL2 release notes for tzdata to find the latest version and when it was installed.

Currently the latest release notes are version 2.0.20221004.0, built on October 10, 2022 and released October 20, 2022. The notes indicate that the package tzdata-2022d-1.amzn2.0.1.noarch was included, which corresponds to the 2022d release from IANA - which was the current at the date the AL2 release was built.

Since then, IANA has released 2022e (on Oct 11) and 2022f (on Oct 29).

You can always update to the latest version that Amazon has built a package for via the command:

yum update tzdata

CodePudding user response：

Does Amazon Linux 2 guarantee that time zone changes are correctly reflected on EC2 instances running Amazon Linux 2?

Yes.

The current time readings of the latest versions of Amazon Linux 2 and Amazon Linux are accurate.

They are automatically synchronised with the Amazon Time Sync Service (ATSS) through NTP. On Amazon Linux 2, chrony is already installed, configured and running to use the Amazon Time Sync Service IP address. ATSS uses satellite-connected & atomic reference clocks in each AWS Region to determine an accutate UTC timestamp.

How often is the timezone database updated on Amazon Linux 2?

Fast enough (default value set by AWS for chrony's minpoll is 4); you can verify this by doing sudo vim /etc/chrony.conf on an EC2 instance

How often is the NTP server updated?

No reference anywhere but it's often enough if the same service is being used internally for AWS services which everyone else depends on.