Ubuntu stuck after the dev/sda1 clean message on startup

that clean message is just the disk check passing, it's not the problem. what's hanging is the login screen loading after it. press ctrl+alt+f3 to get a text login, sign in, and run df -h first - a full root partition stops the desktop starting and looks exactly like this. if there's space, it's usually the graphics driver after an update: at the grub menu press e, add nomodeset to the end of the line starting with linux, then ctrl+x to boot. if that gets you in, reinstall the driver from there.