oe7drt-website/content/notes/archlinux/index.md

---
title: Archlinux
date: 2023-11-29T20:33:48+0100
lastmod: 2024-05-26T06:31:47+0000
tags:
  - archlinux

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---

## Systemd Unit files

A nice and informative article about unit files.

<https://www.digitalocean.com/community/tutorials/understanding-systemd-units-and-unit-files>

## Predictable network interfaces

Get back the "old" interface names like `eth0` or `wlan0` with
{{< man systemd.link 5 >}}.

### Ethernet

This makes my ethernet interface be called **eth0** again.

Create `/usr/lib/systemd/network/80-ether.link` with this content:

~~~systemd
[Match]
Type=ether

[Link]
NamePolicy=keep kernel
~~~

Reboot.

### Wireless

This makes my wireless interface be called **wlan0** again.

Create `/usr/lib/systemd/network/80-wlan.link` with this content:

~~~systemd
[Match]
Type=wlan

[Link]
NamePolicy=keep kernel
~~~

Reboot.

## Setup WiFi networks

### Using **iwctl**

~~~console
$ iwctl device list
$ iwctl station wlan0 scan
$ iwctl station wlan0 get-networks
$ iwctl station wlan0 connect {ssid}
~~~

### Using **nmcli** (NetworkManager)

~~~console
$ nmcli device wifi list
$ nmcli device wifi rescan
$ nmcli device wifi connect {ssid} --ask
$ nmcli device wifi show-password
~~~

Last command shows the connected SSID and a QR-code within the terminal.

## Using NetworkManager

We create some files in `/etc/NetworkManager/conf.d`:

## Using `iwd` as the WiFi backend

`wifi_backend.conf`:

~~~ini
[device]
wifi.backend=iwd
~~~

## Using `dhcpcd` as DHCP client

`dhcp-client.conf`:

~~~ini
[main]
dhcp=dhcpcd
~~~

## Blocking IPs from a list with ipset

Using [ipset](https://wiki.archlinux.org/title/Ipset) should increase performance
on the box, also using the raw table should not create useless states as for what
I understand from the source article on
[serverfault.com](https://serverfault.com/a/823336).

~~~console
$ sudo ipset -N badips iphash
$ while read ip; do sudo ipset -A badips "$ip"; done < blocked.txt
$ sudo iptables -t raw -I PREROUTING -m set --match-set badips src,dst -j DROP
$ sudo iptables-save -f /etc/iptables/iptables.rules
~~~

Enable iptables in case it is not running yet.

~~~console
$ sudo systemctl enable --now iptables.service
~~~

Also make the ipset configuration persistent:

~~~console
$ sudo ipset save -file /etc/ipset.conf
$ sudo systemctl enable ipset.service
~~~

Reboot to test its persistency.

## Do not manage one specific USB dongle

`99-unmanaged-devices.conf`:

~~~ini
[keyfile]
unmanaged-devices=mac:xx:xx:xx:xx:xx:xx
~~~

## Prefer local DNS instead of systemd-resolved defaults

<https://unix.stackexchange.com/a/442599>

## CPU frequency scaling

<https://wiki.archlinux.org/title/CPU_frequency_scaling>

## YubiKeys

<https://wiki.archlinux.org/title/YubiKey>

## LunarVim custom key mappings

I know, this is an Arch Linux post but hey, I don't care.

<https://github.com/LunarVim/LunarVim/issues/2602>

## Mounting nfs shares with systemd

<https://wiki.archlinux.org/title/NFS#Mount_using_/etc/fstab_with_systemd>

### Arch Linux ARM installation on a Raspberry Pi 2

The wiki page is for Raspberry Pi 4.

<https://archlinuxarm.org/platforms/armv8/broadcom/raspberry-pi-4>

## Create a 32-bit Wine prefix

I create my wine prefixes usually like this:

~~~console
$ export WINEPREFIX=/home/dominic/.wine-winlink
$ export WINEARCH=win32
$ wine wineboot
~~~

## Installing multiple ruby versions

I came to the point to test an older website from me and it was made with
Jekyll which I had to install quickly. Problems occured with OpenSSL and I
finally managed to install ruby version 2.7.1 and 3.0.0 in my home directory.

~~~console
$ rvm pkg install openssl
$ rvm install "ruby-3.0.0" --with-openssl-dir=$HOME/.rvm/usr
$ rvm install "ruby-2.7.1" --with-openssl-dir=$HOME/.rvm/usr
~~~

Later in the desired directory, I re-installed the gems because with ruby 2.7.1
I got another "Directory not found" error.

I had to do this because I used ruby 2.7.1 on one website.

~~~console
$ bundle install --force
~~~

## Bigger font for systemd-boot

Edit `/boot/loader/loader.conf`:

~~~
console-mode 0
~~~

Possible settings are:

| Value | Description |
| :---  | :---        |
| 0     | Standard UEFI 80x25 mode |
| 1     | 80x50 mode, not supported by all devices |
| 2     | the first non-standard mode provided by the device firmware, if any |
| auto  | Pick a suitable mode automatically using heuristics |
| max   | Pick the highest-numbered available mode |
| keep  | Keep the mode selected by firmware (the default) |

More details can be found in {{< man loader.conf 5 >}}.

### Manual sections

| Section | Description |
| :---    | :---        |
| 1       | Section 1 of the manual describes **user commands** and tools, for example, file manipulation tools, shells, compilers, web browsers, file and image viewers and editors, and so on |
| 2       | Section 2 of the manual describes the Linux **system calls**. A system call is an entry point into the Linux kernel. Usually, system calls are not invoked directly: instead, most system calls have corresponding C library wrapper functions which perform the steps required (e.g., trapping to kernel mode) in order to invoke the system call. Thus, making a system call looks the same as invoking a normal library function. |
| 3       | Section 3 of the manual describes all **library functions** excluding the library functions (system call wrappers) described in Section 2, which implement system calls. |
| 4       | Section 4 of the manual describes **special files (devices)**. |
| 5       | Section 5 of the manual describes various **file formats**, as well as the **corresponding C structures**, if any. |
| 6       | Section 6 of the manual describes the **games** and funny little programs available on the system. |
| 7       | Section 7 of the manual provides **overviews on various topics**, and describes conventions and protocols, character set standards, the standard filesystem layout, and miscellaneous other things. |

## Encoding videos with ffmpeg

This is not an Arch way of encoding videos, but since I do this on my...

~~~console
$ ffmpeg -i <input> -c:v libx264 -b:v 1M -maxrate 1M -bufsize 2M -pass 1 -f null /dev/null
$ ffmpeg -i <input> -c:v libx264 -b:v 1M -maxrate 1M -bufsize 2M -pass 2 <output>
~~~