stuck in boot after upgrade to 18.04 from ?16.10

I accepted offer to upgrade to 18.04 from, I think, 16.10.
I run Ubuntu from a USB stick in a Lenovo x250.
I had set up an encrypted file system that asks for a password on booting up.

I got several errors on the upgrade last night.
I didn't write all of them down.
The first one is

could not install /var/cache/apt/archives/e2fsprgs_1.44.1-1_amd64.deb

I let the upgrade continue.

This morning the screen said the upgrade had failed.
I tried to see if the machine was busy by running the system monitor, but it didn't come up.
I shut down the machine through clicking on the shutdown button. I didn't just turn it off.

On boot up
I was asked for the password to decrypt the file system..
The boot up didn't finish. The graphics screen changed to text.
My screen is stuck with a page full of text.
The last item says:
[OK] Started GNOME Display manager. Dispatcher Service......before the pop line was shut down.....

The start of the screen has six [OK] then
Stopping User Manager for UID 121...
WARNING: Failed to connect to lvmetad. Falling back to device scanning.
Volume grup "ubuntu-vg" not found
Cannot process volume group ubuntu-vg
WARNING: Failed to lvmetad. Falling back to device scanning.
Reading all physical volumes. THis may take a while....
(this is repeated four times)
Found volume group "ubuntu-vg" using metadata type lvm2
WARNING: Failed to lvmetad. Falling back to device scanning.
2 logical volume(s) in volume group "ubuntu-vg" now active
/dev/mapper/ubuntu--vg-root: clean 554255/7028736 files, 24551477/28106752 blocks
[FAILED] Failed to start Monitoring of LVM2 mirrors, snapshots etc using dmeventd or progress polling.
see 'systemctl status lvm2-monitor.service' for details.
[OK] Started uncomplicated firewall.
rest of page is OK

I've left my machine on.
I'd like to know what to do.