GNS3 couldn’t run /usr/bin/dumpcap in child process: Permission Denied.
Ubuntu 16.04 LTS GNS3: Problem: couldn’t run /usr/bin/dumpcap in child process: Permission Denied.
Solution
Enable non-root user to capture network traffic by reconfiguring wireshark.
gns3a@gns3A:~$ sudo dpkg-reconfigure wireshark-common
Add wireshark group to the user that you want to start GNS3 program.
sudo gpasswd -a $USER wireshark
Logout and Login again.