Tag Archives: fix leap second

Leap Second 2016 may cause Linux to freeze

Leap Second 2016 may cause Linux to freeze :

A leap second will again be inserted at the end of June 30, 2016 at 23:59:60 UTC. Previously, on 30 June, 2012 a leap second was added.

what is it ?

Leap seconds are a periodic one-second adjustment of Coordinated Universal Time(UTC) in order to keep a system’s time of day close to the mean solar time. However, the Earth’s rotation speed varies in response to climatic and geological events, and due to this, UTC leap seconds are irregularly spaced and unpredictable.

So this leap second can  cause your linux kernel deadlock or make database crash .

Just for your information , FreeBSD and Unix are safe as 23:59:60 does not exist in Unix’s implementation of UTC then the linux kernel inserts the leap second by stepping the system clock back by one second on the first clock update after 0:00 UTC

How to fix it :

This problem is solved by either applying Operating System (Linux) patches, resetting the date or rebooting the system. The resolution is dependent on your level of Linux and your environment. Please consult your Linux provider for details of the solution appropriate for your system.

who can i resolve it ?:

  1. Check the Linux kernel version. In theory only 2.6.22 and newer levels should be affected:
    All: uname -r
  2. Switch to root or log in as root at the console
  3. Check to see if NTP is running:
    RHEL: service ntpd status
    SLES: /etc/init.d/ntp status
  4. If NTP is running, disable it:
    RHEL: service ntpd stop
    SLES: /etc/init.d/ntp stop
  5. Set the system clock to the current time:
    All sntp -P no -r pool.ntp.org
    Or: ntpdate 0.us.pool.ntp.org
  6. If NTP was running, reenable it:
    RHEL: service ntpd start
    SLES: /etc/init.d/ntp start

By Hossein Mehrara