Comment 2 for bug 1923699

still on live system

ubuntu@ubuntu:/$ mount |grep target
/dev/sda1 on /target type ext4 (rw,relatime,errors=remount-ro)
/dev/sdb2 on /target/boot/efi type vfat (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
udev on /target/dev type devtmpfs (rw,nosuid,noexec,relatime,size=2430856k,nr_inodes=607714,mode=755,inode64)
ubuntu@ubuntu:/$ df -h
Filesystem Size Used Avail Use% Mounted on
tmpfs 487M 7.6M 479M 2% /run
/dev/sdb1 ubuntu@ubuntu:/$ mount |grep target
/dev/sda1 on /target type ext4 (rw,relatime,errors=remount-ro)
/dev/sdb2 on /target/boot/efi type vfat (rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro)
udev on /target/dev type devtmpfs (rw,nosuid,noexec,relatime,size=2430856k,nr_inodes=607714,mode=755,inode64)
ubuntu@ubuntu:/$ df -h
Filesystem Size Used Avail Use% Mounted on
tmpfs 487M 7.6M 479M 2% /run
/dev/sdb1 2.7G 2.7G 0 100% /cdrom
/cow 2.4G 170M 2.3G 7% /
/dev/disk/by-label/writable 4.7G 23M 4.5G 1% /var/log
tmpfs 2.4G 0 2.4G 0% /dev/shm
tmpfs 5.0M 8.0K 5.0M 1% /run/lock
tmpfs 4.0M 0 4.0M 0% /sys/fs/cgroup
tmpfs 2.4G 508K 2.4G 1% /tmp
tmpfs 487M 108K 487M 1% /run/user/999
/dev/sda1 73G 8.3G 61G 12% /target
/dev/sdb2 4.9M 4.9M 2.0K 100% /target/boot/efi
ubuntu@ubuntu:/$
                2.7G 2.7G 0 100% /cdrom
/cow 2.4G 170M 2.3G 7% /
/dev/disk/by-label/writable 4.7G 23M 4.5G 1% /var/log
tmpfs 2.4G 0 2.4G 0% /dev/shm
tmpfs 5.0M 8.0K 5.0M 1% /run/lock
tmpfs 4.0M 0 4.0M 0% /sys/fs/cgroup
tmpfs 2.4G 508K 2.4G 1% /tmp
tmpfs 487M 108K 487M 1% /run/user/999
/dev/sda1 73G 8.3G 61G 12% /target
/dev/sdb2 4.9M 4.9M 2.0K 100% /target/boot/efi
ubuntu@ubuntu:/$

Boot loader was to go to /dev/sda
Install was to /dev/sda1

Apr 14 04:08:43 ubuntu grub-installer: info: Identified partition label for /dev/sda1: msdos
Apr 14 04:08:44 ubuntu grub-installer: info: Installing grub on '/dev/sda'
Apr 14 04:08:44 ubuntu grub-installer: info: grub-install does not support --no-floppy
Apr 14 04:08:44 ubuntu grub-installer: info: Running chroot /target grub-install --force --target x86_64-efi "/dev/sda"
Apr 14 04:08:44 ubuntu grub-installer: Installing for x86_64-efi platform.
Apr 14 04:08:55 ubuntu grub-installer: grub-install: error: cannot copy `/usr/lib/grub/x86_64-efi-signed/grubx64.efi.signed' to `/boot/efi/EFI/ubuntu/grubx64.efi': No space left on device.
Apr 14 04:08:55 ubuntu grub-installer: error: Running 'grub-install --force --target x86_64-efi "/dev/sda"' failed.

but only 12% of SDA1 is used; it's a clean disk with only this install on it.