dmesg | head
The command returns the logs at boot time, you'll get in the first few lines one starting with Linux version.
That line will have the name of the version.
$ dmesg | head [ 0.000000] Initializing cgroup subsys cpuset [ 0.000000] Initializing cgroup subsys cpu [ 0.000000] Initializing cgroup subsys cpuacct [ 0.000000] Linux version 3.13.0-77-generic (buildd@lcy01-30) (gcc version 4.8.2 (Ubuntu 4.8.2-19ubuntu1) ) #121-Ubuntu SMP Wed Jan 20 10:50:42 UTC 2016 (Ubuntu 3.13.0-77.121-generic 3.13.11-ckt32) [ 0.000000] Command line: root=LABEL=DOROOT ro cgroup_enable=memory swapaccount=1 [ 0.000000] KERNEL supported cpus: [ 0.000000] Intel GenuineIntel [ 0.000000] AMD AuthenticAMD [ 0.000000] Centaur CentaurHauls [ 0.000000] e820: BIOS-provided physical RAM map: [root@574a0820f181 oliviertech.com]#