Domain Name Resolution Failure (CentOS 6.X System)

Problem Description

After a CVM with CentOS 6.x operating system is restarted or the command service network restart is executed against the CVM, domain names cannot be resolved for the CVM.
In addition, the DNS information in the configuration file /etc/resolv.conf is found to be cleared.

Possible Cause

Defects exist in initscripts with versions earlier than 9.03.49-1 in CentOS 6.x operating system due to different grep versions.

Solution

Upgrade the initscripts to the latest version and regenerate DNS information.

Procedure

1. Log in to the CVM and execute the following command to check the initscripts version.

   $rpm -q initscripts
   initscripts-9.03.40-2.e16.centos.x86_64
   

   As shown in the example above, the initscripts version is initscripts-9.03.40-2, which is earlier than the defective version of initscripts-9.03.49-1, so there involves a risk of cleared DNS.
2. Execute the following command to upgrade initscripts to the latest version and regenerate DNS information.

   cat /dev/null > /etc/resolv.conf
   service network restart
   yum makecache
   yum -y update initscripts
   

3. Execute the following command after upgrade to check the version information of initscripts and verify whether the initscripts is upgraded successfully.

   $rpm -q initscripts
   initscripts-9.03.58-1.el6.centos.2.x86_64
   

   The version displayed is different from that before upgrade and is later than initscripts-9.03.49-1, which indicates that the initscripts is upgraded successfully.