Store Git Credentials on Disk

git config credential.helper store

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Sound in Firefox without PulseAudio

1. Uninstall PulseAudio and install apulse instead.
2. As root patch Firefox library:
   patchelf --set-rpath /usr/lib/apulse /usr/lib/firefox/libxul.so
3. In Firefox ‘about:config’ tab insert into ‘security.sandbox.content.write_path_whitelist’ parameter ‘/dev/snd/’ value.

Play YouTube Videos in MPV

• Install Violentmonkey into your browser and add below mentioned JavaScript script into it.
• Create /usr/bin/ytvideo.sh script handler for ytvideo:// URLs using below mentioned Shell code.
• As root create /usr/share/applications/ytvideo.desktop desktop handler for ytvideo:// URLs using below mentioned Desktop code and run update-desktop-database to update desktop specifications.
• Visit a YouTube video page or reload the existing one, click on the video and associate ytvideo:// URL with the above mentioned script.
• Next time YouTube videos will be automatically played by MPV on click.

YouTube Visited Links

To enforce custom color of visited links on YouTube create ~/.mozilla/firefox/default/chrome/userContent.css file with the following content and restart Firefox:

@-moz-document domain(youtube.com) {
        a:visited,
        a:visited .title,
        a:visited .title .yt-deemphasized-text {
                color: purple !important;
        }
}

Find All Hard Links to a File

FILE='/my/hard/link'
find "$(stat -c %m "$FILE")" -xdev -samefile "$FILE"

Disable SSL Certificate Verification in Git

git config --global http.sslVerify false

Compressed Disk Backup

Disk backup with progress bar using parallel gz compression:

pv /dev/sda | pigz > /mnt/backup/disk.gz

ACPI Errors Fixing

An example how to fix the following ACPI errors experienced on some of HP notebooks.

$ dmesg | grep 'ACPI Error'
[    8.397813] ACPI Error: [CFGD] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
[    8.398670] ACPI Error: Method parse/execution failed [\_TZ.PSL] (Node ffff88048d0a8d20), AE_NOT_FOUND (20160831/psparse-543)
[    8.399741] ACPI Error: Method parse/execution failed [\_TZ.GFXZ._PSL] (Node ffff88048d0a8190), AE_NOT_FOUND (20160831/psparse-543)
[    9.119569] ACPI Error: [CFGD] Namespace lookup failure, AE_NOT_FOUND (20160831/psargs-359)
[    9.120266] ACPI Error: Method parse/execution failed [\_TZ.PSL] (Node ffff88048d0a8d20), AE_NOT_FOUND (20160831/psparse-543)
[    9.121184] ACPI Error: Method parse/execution failed [\_TZ.BATZ._PSL] (Node ffff88048d0a8a50), AE_NOT_FOUND (20160831/psparse-543)

1. Install iasl package.
2. Create a directory to which ACPI tables can be extracted and decompiled:

   mkdir ~/acpi
   cd ~/acpi
   acpidump > acpidump
   acpixtract acpidump
   iasl -e ssdt*.dat -d dsdt.dat

3. Examine DSDT and related SSDT tables if necessary. Observe the hierarchy of the structures to properly locate the problematic code. Noting ACPI names consist of up to four letters and can repeat multiple times among the namespaces. Please see ACPICA Documentation for more.
4. In the above mentioned case it turned out that \_TZ.GFXZ._PSL and \_TZ.BATZ._PSL methods call \_TZ.PSL method which fails because of not recognized CFGD object. It seems that the purpose of the last mentioned method is to return number of installed CPU cores. The fix consists of modifying dsdt.dsl file, removing the problematic code and increasing OEM revision.Before:

   DefinitionBlock ("", "DSDT", 2, "HPQOEM", "1909    ", 0x00000001)
   ...
           Method (PSL, 0, Serialized)
           {
               If ((CFGD & 0x01000000))
               {
                   If ((TCNT == 0x08))
                   {
                       Return (Package (0x08)
                       {
                           \_PR.CPU0, 
                           \_PR.CPU1, 
                           \_PR.CPU2, 
                           \_PR.CPU3, 
                           \_PR.CPU4, 
                           \_PR.CPU5, 
                           \_PR.CPU6, 
                           \_PR.CPU7
                       })
                   }
   
                   If ((TCNT == 0x04))
                   {
                       Return (Package (0x04)
                       {
                           \_PR.CPU0, 
                           \_PR.CPU1, 
                           \_PR.CPU2, 
                           \_PR.CPU3
                       })
                   }
   
                   Return (Package (0x02)
                   {
                       \_PR.CPU0, 
                       \_PR.CPU1
                   })
               }
               Else
               {
                   Return (Package (0x01)
                   {
                       \_PR.CPU0
                   })
               }
           }
   

   After:

   DefinitionBlock ("", "DSDT", 2, "HPQOEM", "1909    ", 0x00000002)
   ...
           Method (PSL, 0, Serialized)
           {
                   If ((TCNT == 0x08))
                   {
                       Return (Package (0x08)
                       {
                           \_PR.CPU0, 
                           \_PR.CPU1, 
                           \_PR.CPU2, 
                           \_PR.CPU3, 
                           \_PR.CPU4, 
                           \_PR.CPU5, 
                           \_PR.CPU6, 
                           \_PR.CPU7
                       })
                   }
   
                   If ((TCNT == 0x04))
                   {
                       Return (Package (0x04)
                       {
                           \_PR.CPU0, 
                           \_PR.CPU1, 
                           \_PR.CPU2, 
                           \_PR.CPU3
                       })
                   }
   
                   Return (Package (0x02)
                   {
                       \_PR.CPU0, 
                       \_PR.CPU1
                   })
           }
   

   Just in case here is the diff:

5. Compile the file and create CPIO archive from it which will be used as an initial ramdisk to override the original ACPI table during the kernel boot. Please see DSDT – ArchWiki and Upgrading ACPI tables via initrd for more:

   mkdir -p kernel/firmware/acpi
   iasl -tc dsdt.dsl
   cp dsdt.aml kernel/firmware/acpi
   find kernel | cpio -H newc --create > /boot/acpi_override

6. Edit the boot loader configuration file to include the ramdisk as one of the first ones. For example in case of Arch Linux GRUB2 modify /boot/grub/grub.cfg file to contain the following section for the active kernel:

   initrd /boot/intel-ucode.img /boot/acpi_override /boot/initramfs-linux.img

7. Reboot the system to apply the ACPI fix and verify ACPI table override works and there are no ACPI errors:

   $ dmesg | grep -e 'ACPI Error' -e 'ACPI: DSDT' -e 'ACPI: Table'
   [    0.000000] ACPI: DSDT ACPI table found in initrd [kernel/firmware/acpi/dsdt.aml][0x23eef]
   [    0.000000] ACPI: Table Upgrade: override [DSDT-HPQOEM-1909    ]
   [    0.000000] ACPI: DSDT 0x000000005EFD1000 Physical table override, new table: 0x000000005DB5B000
   [    0.000000] ACPI: DSDT 0x000000005DB5B000 023EEF (v02 HPQOEM 1909     00000002 INTL 20161117)

Vertica User Management

Create testuser with read-only access to testtable in testschema or with read-only access to all tables in testschema.

CREATE USER testuser IDENTIFIED BY 'password123';
GRANT USAGE ON SCHEMA testschema TO testuser;
GRANT SELECT ON testschema.testtable TO testuser;
GRANT SELECT ON ALL TABLES IN SCHEMA testschema TO testuser;

NetworkManager: Disable Sending Hostname to DHCP Server

Edit /etc/NetworkManager/NetworkManager.conf file to contain the following default settings for new connections:

[connection]
ipv4.dhcp-send-hostname=false
ipv6.dhcp-send-hostname=false

Disable sending hostname to DHCP server for already existing connections:

nmcli -t -f uuid connection | while read uuid; do
 nmcli connection modify $uuid \
 ipv4.dhcp-send-hostname false \
 ipv6.dhcp-send-hostname false
done

Restart NetworkManager to apply the settings:

systemctl restart NetworkManager