Remembering the Last Grub OS

If you are dual booting Linux and Windows, you might want to have Grub automatically select the last booted OS instead of just going with the default. The whole trick rests on adding just two lines to /etc/default/grub:

GRUB_DEFAULT=saved
GRUB_SAVEDEFAULT=true

Of course that has to be followed by update-grub:

$ sudo update-grub

Now Grub will track which OS you booted last and preselect that menu entry.

PS: If you have custom menu entries, do not forget that you need to have savedefault option present.

Adding UEFI Windows 10 Menu Entry to Grub

If you install Ubuntu first and Windows later, you’ll notice that it’s not possible to boot into Linux anymore. As Windows boot loader doesn’t really handle Linux, you’ll need to tell Winodws to use Grub.

Once you’re in command prompt with administrative privileges, you can execute:

> bcdedit /set {bootmgr} path \EFI\Ubuntu\grubx64.efi

After reboot Grub will show it’s ugly face and you’ll have another problem – there are no Windows entries.

To get them into Grub menu, one can simply update grub:

$ sudo update-grub

On most Linux distributions this will trigger OS Prober and Windows Boot Manager entry will magically appear. However, if you have OS Prober disabled or you want to disable it in future for some reason, you can add manual entry too:

$ cat << EOF | sudo tee /etc/grub.d/25_windows
#!/bin/sh
exec tail -n +3 \$0
menuentry 'Windows 10' {
  savedefault
  search --no-floppy --set=root --file /EFI/Microsoft/Boot/bootmgfw.efi
  chainloader (\${root})/EFI/Microsoft/Boot/bootmgfw.efi
}
EOF

$ sudo chmod +x /etc/grub.d/25_windows

$ sudo update-grub

In either case, boot menu should now offer you option to get into Windows.

Symbolic Links on VirtualBox Share

If you are running VirtualBox with Linux guest under a Linux host, you will definitely need symbolic links at one point in time. And, while you can do links toward shared folders, you cannot create a link on shared folder itself. You will get something like:

$ ln -s /something /somethingelse
ln: failed to create symbolic link '/somethingElse': Read-only file system

Well, fortunately it’s easy to enable connection on per share basis. Just run the following command on your host (replacing GuestName and ShareName with correct information):

$ VBoxManage setextradata 'GuestName' VBoxInternal2/SharedFoldersEnableSymlinksCreate/ShareName 1

If your machine is running, you will need to fully shut it down (no, restart doesn’t help) and you get to enjoy the full symbolic link glory.

Detecting Status Bar Double-Click in VSCode Extension

If you’re developing Visual Studio Code extension that deals with statusbar, you might have noticed that it’s activated with a single click. Yes, there is no way to specify double-click behavior. But what if you really, really, want that double-click? Well, you can use trickery.

For example, you can use a timer to help you out:

var doubleClickTimerId

vscode.commands.registerTextEditorCommand("statusbar.command", () => {
  if (!doubleClickTimerId) { //if timer still exists, it's a double-click
    doubleClickTimerId = setTimeout(singleClick, 250); //do single-click once timer has elapsed
  } else {
    clearTimeout(doubleClickTimerId) //cancel timer
    doubleClickTimerId = undefined

    //code for double-click
  }
})

function singleClick() {
  clearTimeout(doubleClickTimerId) //cancel timer
  doubleClickTimerId = undefined

    //code for single click
}

On first click this code will setup a callback to be executed in 250 ms. If nothing else happens, after timer has elapsed, function singleClick will be called and your single-click code will be executed.

However, if another click happens before timer elapses, statusbar command will cancel the timer and execute the double-click code.

Final effect is that any clicks slower than 250 ms get detected as independent while all faster clicks get a double-click treatment – exactly what we wanted.

PS: If you’re wondering why I needed this, it was for my Code Point extension. Single click changes between display style for Unicode character while double click sends you to a web page with much more information.