error: cannot open `/boot/efi/EFI/ubuntu/grubx64.efi': Read-only file system.

[Abdulrahman H. Basher]

I don't know why it happened

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.12
ProcVersionSignature: Ubuntu 5.0.0-23.24~18.04.1-generic 5.0.15
Uname: Linux 5.0.0-23-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.7
Architecture: amd64
CasperVersion: 1.394
CurrentDesktop: ubuntu:GNOME
Date: Wed Apr 22 22:38:56 2020
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 18.04.3 LTS "Bionic Beaver" - Release amd64 (20190805)
ProcEnviron:
 LANGUAGE=en_US.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Mike Salvatore (mikesalvatore)]

Thanks for taking the time to report this bug and helping to make Ubuntu better. We appreciate the difficulties you are facing, but this appears to be a "regular" (non-security) bug. I have unmarked it as a security issue since this bug does not show evidence of allowing attackers to cross privilege boundaries nor directly cause loss of data/privacy. Please feel free to report any other bugs you may find.

[Sebastien Bacher (seb128)]

the log has

Apr 22 19:38:13 ubuntu ubiquity: Installing for x86_64-efi platform.
Apr 22 19:38:23 ubuntu kernel: [ 703.524619] FAT-fs (sda2): error, fat_free_clusters: deleting FAT entry beyond EOF
Apr 22 19:38:23 ubuntu kernel: [ 703.524623] FAT-fs (sda2): Filesystem has been set read-only

looks like the filesystem was corrupted