Network-manager
One of the relatively recent additions to KDE/Gnome has been the ‘network-manager’ tool. It attempts to make the life of its users easier by automagically managing your interfaces. I can’t comment on its effectiveness during a normal user’s session, but my experiences were frustrating.
I guess it isn’t fair to say network-manager’s operation was frustrating, but rather that it was running without my knowledge, causing weird behavior. I’m setting up dhcpd in a virtual machine to provide addresses for an isolated network. Normally this requires that you only set up the interface, grab the package, set up the subnets you want to assign addresses to in /etc/dhcp/dhcpd.conf, and start up the daemon. However, this time around, I ran into some problems.
First, I attempted to set up my primary interface to use a static IP. I edited /etc/network/interfaces to set eth0 to use a static IP, set it and its netmask, and then brought the interface back up. The output from ifconfig showed no IP assignment. What!? Thinking it was something I was doing wrong, I brought the interface back down and ignored it while I configured dhcpd.
The dhcpd.conf file isn’t difficult to set up. The subnets to service were declared, as were the address ranges to use when assigning addresses dynamically. When the configuration was done, I attempted to bring up the daemon. /etc/init.d/dhcp3-server start… and… errors. “Not configured to listen on any interfaces?” Ugh. Further digging revealed that dhcpd was looking to serve addresses on a 10.10.1.0 network that I had configured, but the only active interface was listening on a 169.0.0.0 network.
Wait - an interface is up? I took it down! I again checked the syslogs, and sure enough, something is initiating dhclient to find an IP address, and upon failing, is assigning a private IP from the 169.0.0.0 range to my interface. The root cause of it ended up being network manager trying to maintain a connection on the interface utilizing its own configuration. Stopping the network-manager service immediately fixed the problem - bringing up the eth0 interface resulted in it being assigned the static IP I wanted, dhcpd ran without a problem, and I was happy.
I have some gripes with network-manager from this experience.
First, I edited /etc/network/interfaces to make the changes to eth0’s configuration. That is the way changes have been made to interfaces since before I started using Linux. I understand what network manager was trying to do, but two things perplex me. Why did it block my static IP assignment when I tried to bring the interface up? It wasn’t even immediately overridden, there was literally no address assigned to the interface. And also, why, WHY is it ignoring standard configuration files? /etc/network/interfaces should remain the be-all is-all configuration for network interfaces. Using another configuration file just makes things confusing.
Second, I believe the behavior of network-manager needs to be changed. I don’t know how this would be possible, so it may be an unreasonable thought - but if I bring down an interface manually, I don’t want it back up until I manually bring it up. Network-manager bringing up that interface after I had manually taken it down was confusing as all hell, and I certainly don’t use Linux to have my machine work against me.
I have disabled network manager permanently on my system. For a standard user (are there any ’standard’ Linux users?) it may function well, but for anyone that wants control of their machine, I suggest they do the same.
