Edit cPanel nameserver IP’s

As of WHM 11.30, the nameservers’ IP assignments are now read from the Zonefiles and actual DNS queries after recent updates. If you are not seeing the needed IPs in /etc/nameserverips please do not attempt to edit that file, as it is now overwritten by cPanel.

Check under WHM: Main >> DNS Functions >> Nameserver IPs for current nameserverips

(Solutions may depend on the cPanel version)

The updated A entries and/or NS entries are not retained:
Add the needed nameservers to the /etc/hosts file
vim /etc/hosts
Add (append) a new line, one per IP, onto the existing hosts file such as:
123.456.789.012 ns1.domain.com
123.456.789.012 ns1.domain.com ns2.domain.com
Then run the updatenameserverips script:
Check under WHM: Main >> DNS Functions >> Nameserver IPs again to see if it worked, if not continue

Delete the nameserverips.cache file
rm /var/cpanel/nameserverips.cache

Then modify /var/cpanel/nameserverips.yaml to suite
vim /var/cpanel/nameserverips.yaml

Then run the updatenameserverips script again

IO wait Load Tracking

From http://balajitheone.blogspot.com

IO wait load tracking to a process.

How to identify what processes are generating I/O wait load.

An easy way to identify what process is generating your IO Wait load is to enable block I/O debugging. This is done by setting /proc/sys/vm/block_dump to a non zero value like:

echo 1 > /proc/sys/vm/block_dump

This will cause messages like the following to start appearing in dmesg:

bash(6856): dirtied inode 19446664 (ld-2.5.so) on md1

Using the following one-liner will produce a summary output of the dmesg entries:

dmesg | egrep "READ|WRITE|dirtied" | egrep -o '([a-zA-Z]*)' | sort | uniq -c | sort -rn | head
354 md
324 export
288 kjournald
53 irqbalance
45 pdflush
14 portmap
14 bash
10 egrep
10 crond
8 ncftpput

Once you are finished you should disable block I/O debugging by setting /proc/sys/vm/block_dump to a zero value like:

echo 0 > /proc/sys/vm/block_dump


From http://balajitheone.blogspot.com