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

The new su PATH behavior

The su command that's now being packaged with Debian sid has significant change in behavior. In the past, when you did an:

$ su

the PATH would get set to root's PATH. Now, it remains the user's path:

$ su
Password:
# echo $PATH
/home/mithat/bin:/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games:/snap/bin

This means you won't pick up /usr/sbin where a lot of commands you'd typically use with root privileges live.

The fix to this is that you now have to append a dash to the command:

$ su -
Password:
# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin

I don't know whether this impacts gksu or if sudo and/or gksudo are affected. gksu is affected as well, but with gksu there doesn't appear to be a way to get back to the old behavior.

Fixing Skype for Linux scaling

After a long hiatus from (actually a deliberate avoidance of) Skype, I need to install it again -- at least temporarily. And the latest version of Skype for Linux is appears to be an Electron app, which means its scaling on my non-standard 118 dpi screen is seriously wonky.

The typical fix for this with Chrome/Chromium and Electron apps is to pass the --force-device-scale-factor option to the executable. Applying this option to Skype works as well, but you need to dig a bit to find where to add it. I ended up modifying /usr/bin/skypeforlinux so the last line reads:

nnohup "$SKYPE_PATH" --force-device-scale-factor --executed-from="$(pwd)" --pid=$$ "$@" > "$SKYPE_LOGS/skype-startup.log" 2>&1 &