Kernel – Linux Audio Foundation

# RANDOM LINUX TIPS & TRICKS

# Get INFO/VERSION

# Raspberry PI model / revision / serial

```
$ cat /proc/device-tree/model
```

```
$ cat /proc/cpuinfo
```

# SN#:

$ cat /proc/cpuinfo | grep Serial | cut -d ' ' -f 2

# 10000000XXXXXXXX

```
$ cat /proc/asound/version
```

```
$ dpkg -l alsa*
```

# Kernel version

```
$ uname -a
```

# fedora update kernel/system

$ dnf -y update &amp;&amp; dnf -y upgrade

# For example, to add the user linuxize to the sudo group you would run the following command:

```
$ sudo usermod -a -G sudo linuxize
```

# Configure to boot into Raspbian Desktop

```
$ sudo raspi-config
```

# use your arrow keys to navigate to Enable Boot to Desktop and press enter. Select the Desktop login option and press enter.

# Configure to boot into Raspbian Desktop (without raspi-config)

```
$ sudo update-rc.d lightdm disable
```

# Raspberry testing repository

# replace buster by testing in /etc/apt/sources.list

```
$ sudo nano /etc/apt/sources.list
```

# # from
# deb http://raspbian.raspberrypi.org/raspbian/ buster main contrib non-free rpi
# # to
# deb http://raspbian.raspberrypi.org/raspbian/ bullseye main contrib non-free rpi

```
$ sudo apt update
```

# check if process is locked

```
$ ps aux | grep -i apt
```

# kill process (replace pid_id by the process ID number)

```
$ sudo kill pid_id
```

# check if killed

```
$ sudo kill -9 pid_id
```

# Disable DEBIAN 10 GUI:

$ sudo systemctl set-default multi-user.target

```
$ sudo reboot
```

To re-enable the GUI:

$ sudo systemctl set-default graphical.target

```
$ sudo reboot
```

# activate raspberry pi WIFI

```
$ sudo raspi-config
```

# Select “Localisation Options” then select “change WLAN country”

# then enter root

```
$ sudo su
```

# generate wpa_passphrase using your SSID and followed by typing the wifi password
# replace YOUR-SSID by the exact name of your wifi network name

$ wpa_passphrase "YOUR-SSID" &gt;&gt; /etc/wpa_supplicant/wpa_supplicant.conf

# check if the configuration is okay

$ sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

# should contain something like this:
# the country= must contains a 2 letters ISO 3166-1 of your country code

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev

```
update_config=1
```
```
country=GB
```
```
# reading passphrase from stdin
```
```
network={
```
```
ssid="YOUR-SSID"
```

psk=47abc8153891372573fc831a0bab0346b07cb900ada28dc52686359cc60ab9e7

```
}
```

# network IP info

```
$ ifconfig
```

# scan wifi network

```
$ sudo iwlist wlan0 scan
```

# power OFF / ON HDMI raspberry pi

# hdmi OFF

```
$ sudo /opt/vc/bin/tvservice -o
```

# hdmi ON

```
$ sudo /opt/vc/bin/tvservice -p
```

# AMD64 Useful Cmds

# get hostname

```
$ hostnamectl
```

# set hostname

$ sudo hostnamectl set-hostname musiclounge

```
$ sudo nano /etc/hosts
```

127.0.0.1 localhost
127.0.1.1 musiclounge

# The following lines are desirable for IPv6 capable hosts
::1 localhost ip6-localhost ip6-loopback
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters

```
$ sudo reboot
```

# Check your current Ethernet connection speed

# install ethtool utility

```
$ sudo apt-get install ethtool
```

# determine the name of your ethernet interface usually eth0 or enp3s0

```
$ ip a
```

# get the speed

```
$ sudo ethtool eth0 | grep -i speed
```

# get current playback info useful to check if current playback is DSD native (DSD_U32_BE)

$ cat /proc/asound/card*/pcm*p/sub*/hw_params

# in case you have to entry commands from the server console and not from remote PC/SSH session
# you may want to change the keyboard layout
# use the followinf cmd on debian

sudo dpkg-reconfigure keyboard-configuration

Manage USB Power State (Enable Auto-suspend) of DAC

On Linux (including Debian), it is possible to manage USB power states or disconnect a USB device programmatically or automatically after a period of inactivity. Here’s how you can approach this using a Topping D50 III DAC as an example:

The D50 III DAC doesn’t have a sleep mode, so the screen is always on, it could be very useful on audio server configuration to auto-suspend power after a period of inactivity.

List devices attached and identify your DAC:

lsusb

Bus 001 Device 003: ID 152a:8750 Thesycon Systemsoftware & Consulting GmbH D50 III

The device 152a:8750 (Thesycon Systemsoftware & Consulting GmbH D50 III) can be managed using the USB power management options in Linux. Below is a step-by-step guide specific to this device.

ls /sys/bus/usb/devices/

1-0:1.0 1-1:1.0 1-1:1.2 2-0:1.0 4-0:1.0 usb2 usb4
1-1 1-1:1.1 1-1:1.3 3-0:1.0 usb1 usb3

udevadm info -q path -n /dev/bus/usb/001/003

/devices/platform/axi/1000120000.pcie/1f00200000.usb/xhci-hcd.0/usb1/1-1

Based on the `udevadm` output, the USB device is associated with the path `/devices/platform/axi/1000120000.pcie/1f00200000.usb/xhci-hcd.0/usb1/1-1`, which maps to the `1-1` directory in `/sys/bus/usb/devices/`. Here’s how to manage power settings for this device:

Step 1: Verify Device Directory

The device directory is /sys/bus/usb/devices/1-1.

Navigate to the directory to confirm it exists:

   cd /sys/bus/usb/devices/1-1
   ls

You should see files like power, idVendor, and idProduct, which indicate it’s the correct USB device.

Confirm the device ID matches 152a:8750:

   cat idVendor
   cat idProduct

Ensure idVendor is 152a and idProduct is 8750.

Step 2: Enable Autosuspend

Check the current power management state:

   cat power/control

If it says on, the device is not suspending.

Enable autosuspend:

   echo 'auto' | sudo tee power/control

Set the autosuspend delay (e.g., 60 seconds):

   echo '60000' | sudo tee power/autosuspend_delay_ms

These settings will allow the device to enter a low-power state after 60 seconds of inactivity.

Step 3: Automate with `udev` Rules

To make the changes persistent:

Create a udev rules file:

   sudo nano /etc/udev/rules.d/99-usb-autosuspend.rules

Add the following content (in the first line of the file):

ACTION=="add", SUBSYSTEM=="usb", ATTR{idVendor}=="152a", ATTR{idProduct}=="8750", ATTR{power/control}="auto", ATTR{power/autosuspend_delay_ms}="5000"

# CTRL+X to save

Reload udev rules:

   sudo udevadm control --reload-rules
   sudo udevadm trigger --subsystem-match=usb

Step 4: Disable/Enable the Device Manually

Disable the device:

   echo '0' | sudo tee authorized

Re-enable the device:

   echo '1' | sudo tee authorized

Step 5: Test the Configuration

Monitor power state:

   cat power/runtime_status

You should see suspended when the device is in a low-power state.

Verify the autosuspend delay:

   cat power/autosuspend_delay_ms

Troubleshooting

If the device does not suspend, check if it supports USB autosuspend. Some devices might not fully adhere to the USB power management specifications.
Review logs for errors:

   dmesg | grep usb

# TS6

# if MPD doesn’t start type this to get its status

```
$ sudo systemctl status mpd
```

# if the error is related to /libavcodec.so.58: undefined symbol: bcm_host_is_fkms_active
# reinstall libraspberrypi0 pkg

$ sudo apt install --reinstall libraspberrypi0

```
$ sudo reboot
```

# NANO return this error (on Armbian / Debian):

Unable to create directory /root/.local/share/nano/: No such file or directory It is required for saving/loading search history or cursor positions.

# check if nano cmd is available using:

```
sudo /bin/nano .bashrc
```

# if nano opens the file then you simply need to create the /root/.local/share/nano/ directories
# you can confirm the issue by using:

```
sudo ls -l /root/.local/
```

# UPGRADE or DOWNGRADE YOUR KERNEL

# IMPORTANT:
# All information below is for Raspberry PI platform only, does not apply to other devices

# go to
https://github.com/Hexxeh/rpi-firmware/commits/master

# get the sha1 of the kernel
# for example: 4.19.118-v7 e1050e94821a70b2e4c72b318d6c6c968552e9a2

# then to install this old kernel 4.19.118-v7+ enter:

$ sudo rpi-install e1050e94821a70b2e4c72b318d6c6c968552e9a2

```
$ sudo reboot
```

# install pkg ends with error:
# “Failed to start The PHP 7.3 FastCGI Process Manager”
# type the cmd below to create the missing directory:

```
$ sudo mkdir /var/run/php
```

Linux Audio Foundation

Foundation Dedicated To Linux Audio Since 2003

Category: Kernel

MISC: Tips & Tricks

Manage USB Power State (Enable Auto-suspend) of DAC

Step 1: Verify Device Directory

Step 2: Enable Autosuspend

Step 3: Automate with `udev` Rules

Step 4: Disable/Enable the Device Manually

Step 5: Test the Configuration

Troubleshooting

TROUBLESHOOTING: GENERAL

Manage USB Power State (Enable Auto-suspend) of DAC

Step 1: Verify Device Directory

Step 2: Enable Autosuspend

Step 3: Automate with udev Rules

Step 4: Disable/Enable the Device Manually

Step 5: Test the Configuration

Troubleshooting

Step 3: Automate with `udev` Rules