You have no configuration for swap in /etc/fstab . Add following line to that file:
UUID=<uuid> none swap sw 0 0
You have to replace
$ sudo blkid /dev/sda1: LABEL="System Reserved" UUID="88A0D0A1A0D09752" TYPE="ntfs" /dev/sda2: UUID="0620D9F920D9EFA3" TYPE="ntfs" /dev/sda5: UUID="c282b418-2045-4852-8789-88a44360a0bb" TYPE="ext4" /dev/sda6: UUID="f99c6a0c-790a-45ca-a1a9-8874f5a2999b" TYPE="ext4" /dev/sda7: UUID="4cc2e909-ebd1-4c72-abee-aa32035bf330" TYPE="swap"
References
http://askubuntu.com/questions/194775/swap-not-available-i-must-manually-swapon-after-every-reboot