host name
 

what should be the hostname, when i type
#hostname
linux1
and when i type
#hostname -f
linux1
but hostname -f = linux1 is not fqdn. so i set it to
#hostname linux1.acme.com
and then i checked it
#hostname
linux1.acme.com
and when i typed
#hostname -f
linux1.acme.com

i am confused what should i set my hostname, or what is right

The hostname is whatever name you want to call your machine. That's up to you. If your on a domain, you can set your domain name with the command domainname