I'm trying to update pkgin database with pkgin update command but i'm getting following error.
Unable to fetch pkg_summary.gz
That is a network problem. You need to check the network configuration. For example, some virtual boxes have problems with the DHCP (if it isn't setup correctly).
One solution may be to set the address manually. To do so, execute
netconf
and select the manual option. Set the IP address (it should be in the same range of your other network devices), submask, and DNS.