Hacks.Wiki - Today I Learned...

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2023-02-28T00:20:07.14678556+05:30

Welcome to 🏡 Hacks.Wiki - a Wikifull of Hacks

Human beings, who are almost unique in having the ability to learn from the experience of others, are also remarkable for their apparent disinclination to do so. - Douglas Adams

Hacks.Wiki is an experiment to organise quick hacks, notes, bookmarks and tools into an easy-to-build-and-maintain “Digital Garden”.

It should take others far less time and effort to do what we’ve already done.

You can start by visiting Recent entries. Or start by browsing the Hashtags. There is also a RSS Feed that you can subscribe to. And - 🎊surprise - there is an ActivityPub handle as well; Just follow hacks@hacks.wiki via a Mastodon / Pleroma / Soapbox / Misskey and other instances and tools.

Unless otherwise noted, all hacks in this wiki are licensed under CC-BY-4.0.

site/README

2023-02-28T00:11:02+05:30

hacks-wiki ¶

A Wikiful of Hacks: Hacks.Wiki is an experiment to organise quick hacks, notes, bookmarks and tools into an easy-to-build-and-maintain “Digital Garden”.

Migrate from UEFI to (Legacy) BIOS

2023-02-28T00:06:41.560136473+05:30

Migrating Grub from a UEFI system to a BIOS (legacy) system 🔁

The general steps are:

Boot the computer using a live boot image - Eg. System Rescue Image
Mount the root filesystem¹
Bind mount /dev, /sys, /proc and /run²
Change your EFI boot partition to EF02 BIOS boot partition³
Chroot into the mounted file-system
Re-install Grub ⁴

Here is someone who has documented this process in good detail:

Grub Install and Btrfs Root File System | Logan's Note

https://logan.tw/posts/2015/05/17/grub-install-and-btrfs-root-file-system/

#grub #seabios #coreboot #uefi

Mounting BTRFS subvolumes needs an extra option ↩︎
for f in dev sys proc run; do mount --bind /$f /mnt/$f; done ↩︎
Remember to use gdisk if you have a GPT partition table. The BIOS boot partition code is EF02 ↩︎
grub-install /dev/sda ↩︎

Detect UEFI or BIOS

2023-02-28T00:05:52.993470865+05:30

Here is how you can detect if you’ve booted your computer using a UEFI BIOS or a Legacy BIOS. First, install the dmidecode utility from your operating system repository. On Debian, you can:

1apt-get install dmidecode

dmidecode reports information related to the BIOS under a type 0 entry. A quick way to detect the BIOS mode is:

1sudo dmidecode -t 0 | grep UEFI > /dev/null && echo UEFI || echo BIOS

On a (Legacy) BIOS system you would see:

 1$ sudo dmidecode -t 0
 2# dmidecode 3.4
 3Getting SMBIOS data from sysfs.
 4SMBIOS 3.0.0 present.
 5
 6Handle 0x0000, DMI type 0, 26 bytes
 7BIOS Information
 8        Vendor: 3mdeb
 9        Version: Dasharo (coreboot+SeaBIOS) 
10        Release Date: 08/23/2022
11        ROM Size: 12 MB
12        Characteristics:
13                PCI is supported
14                PC Card (PCMCIA) is supported
15                BIOS is upgradeable
16                Selectable boot is supported
17                ACPI is supported
18                Targeted content distribution is supported
19        BIOS Revision: 0.0
20        Firmware Revision: 0.0

On a UEFI system you would see:

 1$ sudo dmidecode -t 0
 2# dmidecode 3.4
 3Getting SMBIOS data from sysfs.
 4SMBIOS 3.1.1 present.
 5
 6Handle 0x0000, DMI type 0, 26 bytes
 7BIOS Information
 8        Vendor: American Megatrends Inc.
 9        Version: 2202
10        Release Date: 07/14/2020
11        Address: 0xF0000
12        Runtime Size: 64 kB
13        ROM Size: 16 MB
14        Characteristics:
15                PCI is supported
16                APM is supported
17                BIOS is upgradeable
18                BIOS shadowing is allowed
19                Boot from CD is supported
20                Selectable boot is supported
21                BIOS ROM is socketed
22                EDD is supported
23                Print screen service is supported (int 5h)
24                8042 keyboard services are supported (int 9h)
25                Serial services are supported (int 14h)
26                Printer services are supported (int 17h)
27                ACPI is supported
28                USB legacy is supported
29                BIOS boot specification is supported
30                Targeted content distribution is supported
31                UEFI is supported
32        BIOS Revision: 5.13

#uefi #seabios #coreboot #bios 👢

Mounting BTRFS subvolumes

2023-02-27T23:42:13.170168807+05:30

If you have installed GNU/Linux with BTRFS as the filesystem, chances are that your OS installer has used sub-volumes for the root, home and other mount points. 🗄️

You can verify this by mounting the actual root filesystem device and listing its contents:

1# ls -l /mnt/
2total 0
3drwxr-xr-x 1 root root  204 Feb 22 13:28 @
4drwxr-xr-x 1 root root  180 Feb 22 14:29 @cache
5drwxr-xr-x 1 root root   10 Dec  2 10:52 @home
6drwxr-xr-x 1 root root  482 Feb 26 00:00 @log
7drwxr-x--- 1 root root  350 Feb 23 15:40 @root
8drwxr-xr-x 1 root root   14 Oct 19 07:42 @srv
9drwxrwxrwt 1 root root 1576 Feb 27 17:18 @tmp

Here @, @home, @log etc. are the BTRFS sub-volumes. @ is the OS root sub-volume. You can mount by giving the -osubvol=@ option to the mount command:

 1# mount -osubvol=@ /dev/dm-0 /mnt/
 2# ls -l /mnt/
 3total 24
 4lrwxrwxrwx 1 root root    7 Feb  1 02:21 bin -> usr/bin
 5drwxr-xr-x 1 root root  208 Feb 22 13:30 boot
 6drwxr-xr-x 1 root root    8 Oct 20 18:39 dev
 7drwxr-xr-x 1 root root 5018 Feb 25 10:56 etc
 8drwxr-xr-x 1 root root    0 Dec  2 10:48 home
 9lrwxrwxrwx 1 root root    7 Feb  1 02:21 lib -> usr/lib
10lrwxrwxrwx 1 root root    7 Feb  1 02:21 lib64 -> usr/lib
11drwxr-xr-x 1 root root   22 Dec 16 13:00 mnt
12drwxr-xr-x 1 root root  214 Feb 23 15:50 opt
13drwxr-xr-x 1 root root    0 Dec  2 10:48 proc
14drwxr-xr-x 1 root root   66 Oct 20 18:47 root
15    ....    ....    ....

#linux #btrfs #systemrescue #filesystem

starred

2023-02-27T23:41:14.286836779+05:30

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Chromebox-Audio

2023-02-27T17:37:52+05:30

🎧 If you have to use a Chromebox with GNU/Linux, the sound might not work right away. To get Intel Corporation Sunrise Point-LP HD Audio working, do do the following:

1  echo "options snd-intel-dspcfg dsp_driver=1" > /etc/modprobe.d/inteldsp.conf

Once you reboot, you should be able to use Audio over HDMI or the built-in headphone jack.

#chromebox #linux #audio