Solving "device not managed" for Ethernet connections in Network Manager

At some point or another, Network Manager in Debian sid stopped managing my Ethernet connection. The source of the issue is /etc/NetworkManager/NetworkManager.conf:

[main]
plugins=ifupdown,keyfile

[ifupdown]
managed=false

The [ifupdown] clause seems to be telling NM not to do it. The solution is to turn the frown upside down, but doing so in NetworkManager.conf means the setting will likely be clobbered the next time NM is updated. The solution to that is to create a file in in conf.d named 10-globally-managed-devices.conf. NM upgrades should leave custom files in conf.d alone.

Source

Ground rules

I was having a really tough time getting things going until I found an article on adapting Ubuntu to low memory situations at Ubuntu’s community documentation site. The basic idea outlined there is to install a text-based system and then manually add lightweight GUI stuff and other applications. One cool thing about this is that we don’t need to limit ourselves to an Ubuntu based install: since Ubuntu is itself based on Debian, it should be possible to do with Debian what the article suggests doing with Ubuntu. The article also mentions the possibility of installing Xubuntu and then replacing the heavier items with lighter alternatives.

So, overall this gives us three different promising paths to follow:
1. A text-based Ubuntu install plus a manually installed GUI environment.
2. A text-based Debian install plus a manually installed GUI environment.
3. A full Xubuntu install with unnecessary stuff removed and heavier items replaced with lighter alternatives.

Approaches similar to the above should also be possible using any other major distribution. However, at this point I want to limit myself to Ubuntu and Debian. These are two very well-supported distributions, and I don't see what will be gained by considering other distributions. Of the major Linux distributions, Ubuntu is the most consumer-oriented. Debian is an attractive alternative to Ubuntu because Ubuntu has a reputation for doing some things in a slightly non-standard way; Debian is an accepted, established, and carefully maintained standard that may overcome some problems presented by using Ubuntu.

I have been working mostly with parallel installs based on 1. and 2. I will postpone working along path 3. until after I have a better understanding of what’s going on. An additive approach to functionality lets you learn what each package, etc. does and gives you a more fully integrated idea of what’s happening. A subtractive approach only tells you what’s not needed—and it doesn’t guarantee that you have a minimal set of what is required. However, I will probably play around coarsely with an Xubuntu install before I have a really good idea what's what to see what might be possible along that path.

Goals

It would probably be a good idea at this point to outline in greater detail what the goals of this little undertaking are. In no particular order:

A Windows 98 alternative. As mentioned on the About page, the primary goal here is to find or develop an operating system for Intel-based machines that are too limited in resources to support Windows XP (or, by extension, Vista) or Canonical’s Xubuntu (or, by extension, Ubuntu).

Windows 98 UI reproduction not a goal. While the goal is to find an OS that is an alternative to Windows 98, reproducing the Windows 98 user interface is not a criterion. I consider it acceptable for the user to have to change the way he or she is used to doing things, in much the same way one would need to adapt to OS X from Windows or vice-versa. By the same token, a solution that resembles Windows 98 or XP (or Mac OS X or OS 9 or any other system for that matter) is fine as well.

Usability. The fact that reproducing the Windows way of doing things is not a goal does not mean that usability is not a goal. Quite the opposite: while the ultimate solution does not need to resemble any popular OS, it must be easy to use by typical computer users. Pushing the envelope to include your grandmother would be great, but I have something closer to my cousins in mind instead as target users.

End-user management. The system needs to be manageable by end-users, not system administrators. It shouldn’t be assumed that the end-user will be satisfied with the applications and configurations that are included in the default distribution/installation. Indeed, this is where a lot of Linux distributions fall short. Many of them essentially place the distribution packager in the role of System Administrator, and that’s not gonna cut it for my purposes.

Stability. It’s gotta be stable enough for everyday use.

At this stage, I don’t want to get into specifics about what particular activities and services the system needs to support. I will merely say that the system should support the kinds of activities and services that are expected from a modern consumer-oriented OS. In reality, it’s going to come down to what I can get away with on the limited hardware.