Debian:
# lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 7.8 (wheezy) Release: 7.8 Codename: wheezy
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# cat /etc/debian_version 7.8
CentOS:
# cat /etc/centos-release CentOS Linux release 7.0.1406 (Core)