Public bug reported:
Package:
cryptsetup-initramfs
Ubuntu release:
Ubuntu 26.04
Summary:
During boot on a LUKS root system, cryptsetup/initramfs emits ignored errors
because realpath is called from initramfs cryptroot/cryptsetup scripts, but the
generated initramfs does not contain a realpath command. Adding
/usr/bin/realpath to the initramfs via a local hook fixes the issue.
Observed behavior:
During boot, I see ignored errors related to realpath missing. Searching the
installed scripts shows realpath is called by stock initramfs/cryptsetup
scripts:
/usr/share/initramfs-tools/scripts/local-bottom/cryptroot:
if [ -d "$d2" ] && d2="$(realpath "$d2")"; then
/lib/cryptsetup/functions:
if [ -d "$d2" ] && d2="$(realpath -e -- "$d2")"; then
/usr/lib/cryptsetup/functions:
if [ -d "$d2" ] && d2="$(realpath -e -- "$d2")"; then
/usr/share/initramfs-tools/hook-functions also references realpath
during initramfs generation.
On the affected system:
lsinitramfs /boot/initrd.img-$(uname -r) | grep -E '(^|/)realpath$'
returns no result.
The initramfs does include BusyBox:
lsinitramfs /boot/initrd.img-$(uname -r) | grep -E '(^|/)busybox$'
usr/bin/busybox
The host BusyBox supports the realpath applet:
busybox --list | grep '^realpath$'
realpath
However, adding a symlink in initramfs from /usr/bin/realpath to
/usr/bin/busybox resulted in:
realpath: applet not found
So the BusyBox inside the generated initramfs apparently does not
provide the realpath applet even though the host busybox command does.
Expected behavior:
If stock cryptsetup/initramfs scripts call realpath during initramfs boot, the
generated initramfs should include a working realpath command, or the scripts
should avoid assuming realpath exists.
Workaround:
Creating this local hook fixes the boot-time realpath errors:
/etc/initramfs-tools/hooks/realpath
#!/bin/sh
set -e
PREREQ=""
prereqs() {
echo "$PREREQ"
}
case "$1" in
prereqs)
prereqs
exit 0
;;
esac
. /usr/share/initramfs-tools/hook-functions
copy_exec /usr/bin/realpath /usr/bin/realpath
Then:
chmod 0755 /etc/initramfs-tools/hooks/realpath
update-initramfs -u -k "$(uname -r)"
After rebuilding, this confirms the workaround:
lsinitramfs /boot/initrd.img-$(uname -r) | grep -E 'usr/bin/realpath$'
usr/bin/realpath
Impact:
The system still boots, but the error appears during early boot on a LUKS root
system and is confusing/noisy in exactly the path where users need reliable
diagnostics. It may also break scripts that require realpath rather than
treating it as optional.
Suggested fix:
cryptsetup-initramfs/initramfs-tools should ensure a working realpath command
is present in the initramfs when scripts that call realpath are included, or
change those scripts to use a safe fallback.
ProblemType: Bug
DistroRelease: Ubuntu 26.04
Package: cryptsetup-initramfs 2:2.8.4-1ubuntu4
ProcVersionSignature: Ubuntu 7.0.0-27.27-generic 7.0.6
Uname: Linux 7.0.0-27-generic x86_64
ApportVersion: 2.34.0-0ubuntu2
Architecture: amd64
CasperMD5CheckResult: pass
Date: Sat Jul 11 14:09:34 2026
InstallationDate: Installed on 2025-01-05 (552 days ago)
InstallationMedia: Ubuntu-Server 24.04.1 LTS "Noble Numbat" - Release amd64
(20240827)
PackageArchitecture: all
ProcEnviron:
LANG=en_US.UTF-8
PATH=(custom, no user)
SHELL=/bin/bash
TERM=xterm-256color
XDG_RUNTIME_DIR=<set>
SourcePackage: cryptsetup
UpgradeStatus: Upgraded to resolute on 2026-06-26 (15 days ago)
** Affects: cryptsetup (Ubuntu)
Importance: Undecided
Status: New
** Tags: amd64 apport-bug resolute
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https://bugs.launchpad.net/bugs/2160412
Title:
Ubuntu 26.04 cryptsetup initramfs scripts call realpath but initramfs
does not include /usr/bin/realpath
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