Cisco Router boot configuration

File Systems:
system: (RAM, where running-config is kept)
nvram: (NVRAM, where startup-config is saved)
bootflash: (Internal Flash memory)
slot0: (First PCMCIA slot)
slot1: (Second PCMCIA slot)

Copying:
#copy ftp: system:running-config
#copy ncp: system:running-config
#copy tftp: system:running-config

#copy ftp: nvram:startup-config
#copy rcp: nvram:startup-config
#copy tftp: nvram:startup-config

#copy system:running-config nvram:startup-config

Booting:

#show bootvar (verify the contents of the CONFIG_FILE environment variable.)
#boot config dest-flash-url (Set the CONFIG_FILE environment variable.)

#boot network ftp:[[[//[username[:password]@]location]/directory]
/filename]
#boot network rcp:[[[//[username@]location]/directory]/filename]
#boot network tftp:[[[//location]/directory]/filename]
#service config (Enable the router to download config-files at startup)

#boot system

Other Useful commands:
#service compress-config
#boot buffersize bytes (The buffer that holds the configuration file is usually the size of NVRAM. Larger configurations need larger buffers. )
(config)#config-register value
#dir [flash-filesystem:]

Examples
#copy system:running-config tftp://172.16.1.130/istanbul-config
#copy system:running-config ftp://netadmin1:mypass@172.16.101.101/Ankara-config
#copy rcp://netadmin1@172.16.101.101/host1-confg system:running-config
#copy slot0:4:ios-upgrade-1 nvram:startup-config


Ref: Rebooting and Reloading - Configuring Image Loading Characteristics @ Cisco
Cisco IOS Conf. Fundamentals Command Reference Boot Commands