Hello
I setup nameserver in my RHEL 6.2 in cat /etc/resolv.conf

nameserver 192.168.0.1

but after reboot the nameserver string was deleted from resolv.conf !
Why? What service clear my resolv.conf?!

It is probably being done by the DHCP client system. Possible solution here.

EDIT: or the RHEL way here.

I don't use DHCP, only static IP

Ah. That's going to require some detective work.

I would add a boot script that is run at every startup and shutdown level that copies /etc/resolv.conf to try and get a handle on when it is being modified. Because this may need to be done when only the / file system is mounted, I would write to the /etc/ directory rather than the obvious /tmp (unless /tmp is on / and is not emptied durin shutdown-boot). Assuming /tmp is not on / I would run cp -p /etc/resolv.conf /etc/resolv.conf.[KS]<n> where [KS] is K for the shutdown levels and S for the startup levels and <n> is the level.