UTC in Microsoft Windows

To dual boot with Windows, it is recommended to configure Windows to use UTC, rather than Linux to use localtime. (Windows by default uses localtime)

It can be done by a simple registry fix: Open regedit and add a DWORD value with hexadecimal value 1 to the registry HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\TimeZoneInformation\RealTimeIsUniversal

You can do this from an Administrator Command Prompt running:

C:\>reg add "HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TimeZoneInformation" /v RealTimeIsUniversal /d 1 /t REG_DWORD /f

pacman upgrade packages in ArchLinux

pacman upgrade packages in ArchLinux
sudo pacman -Syu
-S – Synchronizes packages
-y – Refreshes the package database
-u – Upgrades all installed packages

Remove a package (keep dependencies)
sudo pacman -R package_name

Remove a package and unneeded dependencies
sudo pacman -Rns package_name

Remove orphaned packages (unneeded dependencies)
sudo pacman -Rns $(pacman -Qdtq)

Remove a package and ignore dependencies
sudo pacman -Rdd package_name

Remove a package and its cache (free up disk space)
sudo pacman -R package_name && sudo pacman -Sc

For a more aggressive cleanup, remove all cached package files:
sudo pacman -R package_name && sudo pacman -Scc

To install packages from a previously saved list of packages, while not reinstalling previously installed packages that are already up-to-date, run:
pacman -S --needed - < pkglist.txt

GRUB boot to last OS

edit /etc/default/grub

change or aadd:

GRUB_DEFAULT=saved

GRUB_SAVEDEFAULT=true

GRUB_DISABLE_OS_PROBER=false

Recreate config

Arch example:

grub-mkconfig -o /boot/grub/grub.cfg

EFI BOOT ENTRY

DELETE

To delete a menu entry using efibootmgr
first list the current boot entries with sudo efibootmgr
Identify the boot number of the entry you want to delete, then use the command:
sudo efibootmgr -b XXXX -B
replacing XXXX with the boot number of the entry you wish to remove.

ADD

To add a menu entry using efibootmgr, use the following command format:
sudo efibootmgr -c -d /dev/sdX -p NN -L "Label" -l "\EFI\path\to\boot\file.efi"
where /dev/sdX is your disk, NN is the partition number,
“Label” is the name you want for the boot entry,
and \EFI\path\to\boot\file.efi is the path to the EFI executable.

!!! Make sure the path to the boot file is correct and uses backslashes, as required by the EFI specification!!!