Is there anything (specifically in linux machines) that can jump from client to server that would have the ability to perform a root-level task, such as stopping a service in an automated manner? (regardless of service)Example:A DHCP server running from dnsmasq on the server side issues an address to a client.  The client receives the address and somehow tells the server ok, we're all good, you can stop dnsmasq now.  Can this be done?  If so, how?In full awareness this would be a colossal security hole, I'm guessing some kind of authentication would need to be involved in many cases, but I'm mostly curious if it's even possible.  I can't think of an instance where I've seen it done.
is it possible to have a dhcp client stop the dhcp service of the server after receiving an address?
services;remote control
A secure way is to do this through ssh. Create a service-specific user (dhcpkiller) and a private/public key pair so that the client can run this command:ssh dhcpkiller@dhcpserver pkill dnsmasqThis one-line script gets triggered by your dhcp environment, which can happen in various ways, depending on the DHCP suite on the client. Quoting from dhclient / RHEL manpages: Immediately after dhclient brings an interface UP with a new IP  address, subnet mask,  and  routes, in the REBOOT/BOUND states, it  will check for the existence of an executable  /etc/dhcp/dhclient-up-hooks script, and source  it  if  found. This   script can handle DHCP options in the environment that are not handled  by default.When dhclient needs to invoke the client configuration script, it  defines a set of  variables  in  the environment, and then invokes  /sbin/dhclient-script.  In all cases, $reason is set to the name of  the reason why  the  script  has  been invoked.   The following  reasons are currently defined: MEDIUM, PREINIT, BOUND, RENEW, REBIND,  REBOOT, EXPIRE, FAIL, STOP, RELEASE, NBI and TIMEOUT