Make TFTP

TFTP (Trivial File Transfer Protocol), a simple form of the File Transfer Protocol (FTP). TFTP uses the User Datagram Protocol (UDP)and provides no security features. It is often used by servers to boot diskless workstations, X-terminals, and to backup routers configurations files.

To install it in Debian or ubuntu:

#apt-get install tftpd tftp
edit /etc/xinetd.d/tftp file, if file doesnt exist create one.

service tftp

{

disable = no

socket_type = dgram

protocol = udp

wait = yes

user = root

server = /usr/sbin/in.tftpd

server_args = -s /tftpboot

per_source = 11

cps = 100 2

flags = IPv4

}

Create a directory called tftpboot in root
#mkdir /tftpboot
Change mode of the directory
#chmod 777 tftpboot
Restart xnetd
#/etc/inid.d/xinetd restart
Now test your connections
#tftp 192.168.10.10
Telnet to your cisco router and start backing up your configuration files.

Reference :
http://shirwa.wordpress.com/2007/11/15/backing-cisco-configuration-file-using-tftpd-in-linux/
http://linux.die.net/man/8/tftpd
http://www.tek-tips.com/viewthread.cfm?qid=532990
http://superuser.com/questions/670503/cant-create-new-files-on-tftp-server