No, don't do that. You are logged in to the installed, mounted partition...
Actually, I just read that the dpkg-reconfigure is only temporary, so it wouldn't work.
Mount everything again and chmod in it, then follow this guide, specifically, the "Permanently Configure keyboard in Ubuntu" section.
Edit: I think ar is Arabic, so run L='ar' && sudo sed -i 's/XKBLAYOUT=\"\w*"/XKBLAYOUT=\"'$L'\"/g' /etc/default/keyboard I guess.
Edit 2: Also, for your general information, in case something else happens, and you need to edit say grub, then you might also need to mount the EFI partition before chmod, but in this case, you did not need to mount /boot/efi because we are not editing it or using it.
Edit 3: Ok, last edit for real. Usually, its better to copy and paste from terminal rather than giving a screenshot. It's easier to read and saves storage on server.