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AWS Commences EC2 Reboot To Fix Xen Bug

Starting on Thursday evening, Amazon Web Services Inc. (AWS) will be rebooting select Elastic Compute Cloud (EC2) instances across all regions and availability zones.

The company privately e-mailed affected customers on Wednesday, and gave more details about the reboot in a blog post Thursday. AWS describes the planned reboot as a "timely security and operational update" that is being made in response to an upcoming Xen security update. However, AWS said it is waiting until next Wednesday, when the Xen security report is made public, to give a fuller explanation for the reboot.

"These updates must be completed by [Oct. 1] before the issue is made public as part of an upcoming Xen Security Announcement (XSA)," according to the AWS blog. "Following security best practices, the details of this update are embargoed until then. The issue in that notice affects many Xen environments, and is not specific to AWS."

The reboot is not related to the so-called "Bash" bug discovered by researchers on Wednesday, AWS said.

According to a FAQ about the reboot by AWS partner RightScale Inc., the reboot will start on Sept. 26 at 2:00 UTC/GMT (Sept. 25 at 7:00 p.m. PDT) and end on Sept. 30 at 23:59 UTC/GMT (Sept. 30 at 4:59 p.m. PDT).

AWS has said that less than 10 percent of its EC2 fleet will be affected.

"The instances that need the update require a system restart of the underlying hardware and will be unavailable for a few minutes while the patches are being applied and the host is being rebooted," AWS said. "While most software updates are applied without a reboot, certain limited types of updates require a restart. Instances requiring a reboot will be staggered so that no two regions or availability zones are impacted at the same time and they will restart with all saved data and all automated configuration intact. Most customers should experience no significant issues with the reboots.

According to one AWS customer commenting on the company's forums, AWS had warned affected customers that they would not be able to avoid the reboots by relaunching instances. An AWS moderator clarified that customers will be able to stop and start instances, but they may not get a patched host.

The reboot will not affect T1, T2, M2, R3, and HS1 instances of EC2, according to RightScale. The company cautioned that other AWS services -- including RDS, ElastiCache, and RedShift -- may experience some downtime during the reboot period.

About the Author

Gladys Rama is the senior site producer for Redmondmag.com, RCPmag.com and MCPmag.com.

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