To specify an installation source for Fedora, CentOS, Red Hat or Scientific Linux, use the linux repo= option at the boot prompt:
For example:
linux repo=cdrom:device linux repo=ftp://username:password@URL linux repo=http://URL linux repo=hd:device linux repo=nfs:options:server:/path linux repo=nfsiso:options:server:/path
In these examples, cdrom refers to a CD or DVD drive, ftp refers to a location accessible by FTP, http refers to a URL accessible by HTTP, hd refers to an ISO image file accessible on a hard drive partition, nfs refers to an expanded tree of installation files accessible by NFS, and nfsiso refers to an ISO image file accessible by NFS.
See here for more information on Anaconda boot options.
