To solve another problem I am having, it has been suggested that I need to "reboot to secure (actually recovery) mode". I don’t know exactly what this means.
I have been in the BIOS of my Dell XPS laptop and I have ensured that Enable Secure Boot is switched on. Does that mean that I am already securely booting?
>Solution :
To boot into recovery mode, follow the steps in Takkat’s answer, which I also mention here.
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Before the Plymouth (boot splash) screen appears, press the Shift or Esc key (could be another key, as it depends on the laptop’s manufacturer) to enter the GRUB boot menu.
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After you’re in the GRUB menu, select
Advanced options for Ubuntu.
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In the advanced options, select a recovery kernel.
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Wait till you get to the Recovery Menu:
In the Recovery Menu you’ll find a few recovery options for your system.
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resume– Boot normally to your main OS. -
clean– This option cleans your OS and removes obsoleted and unnecessary packages. -
dpkg– Try to fix package manager issues. -
failsafeX– Start the system in Safe graphics mode. -
fsck– Check errors in the file system. This option won’t work in recent Ubuntu systems as the disk is mounted. -
grub– Updates the GRUB boot loader. -
network– Enable network services. -
root– It will drop you to a root prompt to execute commands as therootuser. -
system-summary– Shows information about your system.