Leave project running

If for some reason you exit the GNS3 client or it crashes, you do not want the classroom virtual network to be terminated. Under File > Edit Project ensure that "Leave this project running in the background when closing" is checked. Do this for each topology you use (CNDO, NMM)

Edit project


If you restore the entire project from a snapshot - using Edit > Manage Snapshots - then this flag is reset. Remember to set it again afterwards.

For the NOC, you can check all three boxes so your NOC VM auto-starts as soon as the server boots.

Locked objects

Devices are "locked" in position, so you can't accidentally move them around or delete them. Should you wish to do so, then right-click and "Unlock Item"

Configuration management web page

The GNS3 GUI currently does not have a way to restore individual devices from snapshot, or export/import devices of individual IOSv devices (e.g. for password recovery)

Until those features are added, we have written a small CGI tool to perform those functions.

Once you have installed the nsrc-web apache configuration, this tool should be available at http://www.ws.nsrc.org/admin/gns3man. You will need to login using the GNS3 username and password.

Using this tool, you can:

  • Start and stop individual devices
  • Edit the NVRAM configuration for an individual device. This will halt the device, allow you to edit the configuration, and upload it
  • Restore one or more devices from a named snapshot


Whenever you update the kernel, you will need to re-run the command:

sudo chmod +r /boot/vmlinuz-*

This is because the CGI uses libguestfs to read and write the IOSv NVRAM, and this in turn needs to read your kernel to start a temporary virtual machine. If it cannot read the kernel, it will generate this error:

libguestfs: error: /usr/bin/supermin exited with error status 1.


If gns3man gives "Internal Server Error", check the suexec logs in /var/log/apache2/suexec.log.

The program in /etc/apache2/nsrc-web/cgi-bin/gns3man and its enclosing directory must be owned by the "gns3" user and group but not group-writeable. The full suexec security policy is described here.