Change the Default Sound Card on Arch Linux

i found the sound module of my tv card was the default sound device because i tried to run amixer and got no master or pcm controls.

1. discover your sound card model name with lspci and your ALSA driver module names with ls

$ ls -l /sys/module/snd/holders
total 0
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 saa7134_alsa -> ../../saa7134_alsa
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_hda_codec -> ../../snd_hda_codec
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_hda_codec_realtek -> ../../snd_hda_codec_realtek
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_hda_intel -> ../../snd_hda_intel
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_hwdep -> ../../snd_hwdep
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_mixer_oss -> ../../snd_mixer_oss
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_pcm -> ../../snd_pcm
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_pcm_oss -> ../../snd_pcm_oss
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_rawmidi -> ../../snd_rawmidi
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_seq -> ../../snd_seq
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_seq_device -> ../../snd_seq_device
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_seq_oss -> ../../snd_seq_oss
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_timer -> ../../snd_timer
lrwxrwxrwx 1 root root 0 2009-08-13 09:21 snd_usb_audio -> ../../snd_usb_audio

2. add order setting for the module of main soundcard to modprobe.conf

vi /etc/modprobe.d/modprobe.conf
--

options snd_hda_intel index=0

3. make your user be able to use the sound card

gpasswd -a username audio

3. reboot then make sure the sound modules have been loaded

lsmod | grep ^snd_

4. the current version of alsa installs with all channels muted by default. use alsamixer to unmute the channels and adjust volume manually

5. run alsactl once to create /etc/asound.state

alsactl store
# restore
# alsactl restore

6. add alsa to daemons in rc.conf to store the mixer settings on every shutdown and restore them when you boot.

Creat filesystem index for searhing purpose on Unix

if there are no updatedb and locate commands available, this is an alternative method on any unix-like os

1. using find to produce a list of all files' name and path

find / > fsindex

2. search for file

grep keyword fsindex


Add an ip or a range to the whitelist of MoBlock on CentOS

1. if there's an IP address you need to whitelist, find the entry in /etc/moblock/guarding.p2p, for example:

FooBar, inc:192.0.34.164-192.0.34.168

2. you need to make a basic regular expression for grep from this line and put it in /etc/moblock/whitelist. To match the exact line, you need to put a backslash (\) before every metacharacter (\, ., ^, $, [) and put a caret ^ at the beginning and a dollar sign $ at the end. In this example, a valid expression is:

^FooBar, inc:192\.0\.34\.164-192\.0\.34\.168$

see the manpages for grep for more information.