systemd: Reacting to USB NIC hotplugging (post-up scripting)

The problem Using Linux Mint 19, I have a network device that needs DHCP address allocation connected to a USB network dongle. When I plug it in, the device appears, but the DHCP daemon ignored eth2 (the assigned network device name) and didn’t respond to its DHCP discovery packets. But restarting the DHCP server well [...]

A VoIP phone at home: The tech details on leaving your phone company

Introduction This is some information and hard-learned wisdom I collected while setting up an Israeli phone number for use with a VoIP phone, so I can accept calls with a regular Israeli phone number and also make outbound calls. Important to note is that I did this without the local ISPs that provide this service. [...]

MySQL, OOM killer, overcommitting and other memory related issues

It started with an error message This post is a bit of a coredump of myself attempting to resolve a sudden web server failure. And even more important, understand why it happened (check on that) and try avoiding it from happening in the future (not as lucky there). I’ve noticed that there are many threads [...]

AudioCodes MP202B hacking notes (Netvision)

This is a no-go These are notes during my failed attempts to turn an old (2011?) Israeli ISP provider’s SIP adapter (MP202B, provided by Netvision) into one that works with any SIP provider. The first step is to get access of its configuration, and that’s exactly where it stopped. Netvision has taken action to prevent [...]

Linux / X-Windows: Which process owns this window?

Once in a while, there’s a piece of junk on the desktop, and the question is who should be blamed for it. The short answer is: $ xwininfo and fetch the window’s ID from the line at the beginning saying e.g. xwininfo: Window id: 0x860000a “xclock” And next, fetch the alleged process ID: $ xprop [...]

Linux: Permanent graphics mode (resolution) on Cinnamon

The goal Quite simple: Set a fixed graphics mode on the computer screen. More precisely, make Cinnamon (version 3.2.6) on Linux Mint 18.1 (Serena) show the desktop with a predefined resolution, no matter what happens. Spoiler: I failed. But I got close enough for practical purposes, and collected a lot of knowledge while trying. So [...]

Making a snapstot of a full Ubuntu / Mint repository on the local disk

What’s that good for? This isn’t about maintaining a local repository that mirrors its original, following along with its changes. The idea is to avoid the upgrades of a lot of packages every time I want to install a new one with apt. Maybe I should mention that I don’t allow automatic upgrades on my [...]

apt / dpkg: Ignore error in post-install script

You have been warned This post shows how to cripple the installation of a Debian package, and make the system think it went through OK. This might very well bring your system’s behavior towards the exotic, unless you know perfectly what you’re doing. In some few cases, like the one shown below, it might actually [...]

Linux: Command-line utilities for obtaining information

There are many ways to ask a Linux machine how it’s doing. I’ve collected a few of them, mostly for my own reference. I guess I’ll add more items as I run across new ones. General Info inxi -Fxxxz (neat output, but makes the system send me security “password required” alert mails because of attempts [...]

Linux: Atheros QCA6174′s Bluetooth disappearing after reboot

When Bluetooth goes poof Having rebooted my computer after a few months of continuous operation, I suddenly failed to use my Bluetooth headphones. It took some time to figure out that the problem wasn’t with the Cinnamon 3.8.9 fancy stuff, nor the DBus interface, which produced error messages. There was simply no Bluetooth device in [...]