Allowing normal users to access dmesg

New Ubuntu releases prevents normal user from running the dmesg command. But you can restore the original permission running this command:

$ sudo sysctl -w kernel.dmesg_restrict=0

You can make it permanent this way:

echo 'kernel.dmesg_restrict=0' | sudo tee -a /etc/sysctl.conf

Source: https://www.cyberciti.biz/faq/how-to-prevent-unprivileged-users-from-viewing-dmesg-command-output-on-linux/