The NSM appliance software runs on the CentOS Linux operating system.
Juniper has released NSM3000, NSM4000 and NSMXpress updates on CentOS 4.x, 5.7 and 6.5.

After the end of 2015, Juniper will continue to support only CentOS 6.5 for the NSM appliances.
If the NSM appliance is running Centos 4.x or 5.7, please update to Centos 6.5 using the NSM Appliance upgrade available on the Juniper support site.
Follow the section in the upgrade guide to upgrade to CentOS 6.