systemd: Shut down computer at a certain uptime

Motivation Paid-per-time cloud services. I don’t want to forget one of those running, just to get a fat bill at the end of the month. And if the intended use is short sessions anyhow, make sure that the machine shuts down by itself after a given amount of time. Just make sure that a shutdown [...]

Systemd services as cronjobs: No process runs away

But why? Cronjobs typically consists of a single utility which we’re pretty confident about. Even if it takes quite some time to complete (updatedb, for example), there’s always a simple story, a single task to complete with a known beginning and end. If the task involves a shell script that calls a few utilities, that [...]

Root over NFS remains read only with Linux v5.7

Upgrading the kernel should be quick and painless… After upgrading the kernel from v5.3 to 5.7, a lot of systemd services failed (Debian 8), in particular systemd-remount-fs: ● systemd-remount-fs.service – Remount Root and Kernel File Systems Loaded: loaded (/lib/systemd/system/systemd-remount-fs.service; static) Active: failed (Result: exit-code) since Sun 2020-07-26 15:28:15 IDT; 17min ago Docs: man:systemd-remount-fs.service(8) http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems Process: [...]

When umount says target is busy, but no process can be blamed

A short one: What to do if unmount is impossible with a # umount /path/to/mount umount: /path/to/mount: target is busy but grepping the output of lsof for the said path yields nothing. In other words, the mount is busy, but no process can be blamed for accessing it (even as a home directory). If this [...]

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 [...]

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 [...]

systemd / DBus debugging starter pack

Introduction Trying to solve a 90 second wait-on-some-start-job on each boot situation, I found that there’s little info on how to tackle a problem like this out there. Most web pages usually go “I did this, hurray it worked!”, but where do you start solving a problem like this if none of the do-this-do-that advice [...]

Solved: systemd boot waits 90 seconds on net-devices-eth0

Introduction After installing wireshark (and tons of packages it depends on) on a rather fresh and bare-boned Debian 8 (Jessie), I got the “A start job is running for sys-subsystem-net-devices-eth0.device” message for a minute and half on every boot. It was exceptionally difficult to find the reason, because so many packages were installed along with [...]

Replacing ntpd with systemd-timesyncd (Mint 18.1)

Introduction It all began when I noted that my media center Linux machine (Linux Mint 18.1, Serena) finished a TV recording a bit earlier than expected. Logging in and typing “date” I was quite surprised to find out that the time was off by half a minute. The first question that comes to mind is [...]

Upgrading to Linux Mint 19, running the old system in a chroot

Background Archaeological findings have revealed that prehistoric humans buried their forefathers under the floor of their huts. Fast forward to 2018, yours truly decided to continue running the (ancient) Fedora 12 as a chroot when migrating to Linux Mint 19. That’s an eight years difference. While a lot of Linux users are happy to just [...]