Consider you want to have only a local revision control for some single files, e.g. confguration files below /etc. A remote server or centralized storage might be an overhead, so lets do revision control locally in the same director with RCS. This is an example to handle /etc/hosts with RCS. It assumes, that you don't care about locking other users out, as it is only used by root anyway.

To initially create the revision control file inside /etc/RCS/ (i.e. locally) with the current file hosts as initial version.

cd /etc
mkdir RCS
ci -l -d hosts

To checkin further updates, use

ci -l -d hosts

the -l is needed, as RCS by default removes files on checkin. This will keep it checked out and locked (for further editing)

To do a rollback to version 1.3 , use

co -r1.3 -M hosts

To list all versions with changelog information, use

rlog hosts

To compare the current file with the last version checked in, do

rcsdiff hosts

To compare versions 1.2 and 1.4, use

rcsdiff -r1.2 -r1.4 hosts