GRUB

Commands What it does
sed -i 's/^GRUB_CMDLINE_LINUX_DEFAULT="/&option /' /etc/default/grub adds kernel option to GRUB file

Replace &option with the kernel param like quiet or similar.

You will need to run this command when making changes to GRUB's file before rebooting
sudo update-grub

Editing the /etc/default/grub file and changing the GRUB_DEFAULT line to match this will boot the previous kernel as the default:

GRUB_DEFAULT="1>3"

Run the update-grub command to save that change.

fwupd

Commands What it does
fwupdmgr get-devices List devices supported by fwupd
fwupdmgr get-updates Perform updates to devices supported by fwupd

Ubuntu/Pop

apt/dpkg

Commands What it does
apt policy packagename Package information
apt-cache madison packagename List available versions for a package
sudo apt install packagename –dry-run See what packages will be installed with the package
apt policy packagename Find version installed and available
sudo dpkg –remove –force-remove-reinstreq package_name Remove broken package
sudo apt-mark hold packagename Hold a package to the current version
dpkg –list grep linux-image
apt list –installed grep packagename

kernel commands

Commands What it does
sudo update-initramfs -c -k kernelversion Generate a new initramfs image with version

flatpak

Commands What it does
flatpak update Update flatpak packages
flatpak list Show the installed flatpak packages
flatpak search Search flatpak packages from sources
flatpak remotes List Flatpak remotes (other servers)

Plasma

Commands What it does
kioclient exec path/to/desktop/file Runs the .desktop file

GNOME

GSettings

Commands What it does
gsettings set org.gnome.desktop.interface scaling-factor 2 Change scaling for the UI
gsettings set com.ubuntu.user-interface.desktop cursor-size 48 Enlarge cursor
gsettings set org.gnome.desktop.background picture-uri 'file://PathToImage' Change wallpaper
gsettings set org.gnome.desktop.wm.preferences button-layout "appmenu:minimize,maximize,close" Enable Minimize and Maximize buttons