There is no way to set the kerberos (krb5) credential cache name for cifs.upcall

[Karl O. Pinc]

When the krb5 credential cache file name differs from that compiled into cifs.upcall, cifs.upcall can no longer be used.

Mounting fails when the credential cache used by krb5 differs from that used by cifs.upcall. Journalctl shows messages like:

...krb5_child[4725]: No credentials cache found (filename: /tmp/krb5cc_127408622_wH2NwY

I don't know enough to say what the configuration mechanism should be to get the credential cache filename to cifs.upcall. Maybe request-key.conf(5), or maybe something else. But at the moment there seems to be no way to have cifs.upcall work when krb5 is configured to use an "alternate" credential cache.

See also Ubuntu bugs: #2012140 #2012143
https://bugs.launchpad.net/ubuntu/+source/krb5/+bug/2012140
https://bugs.launchpad.net/ubuntu/+source/cifs-utils/+bug/2012143

ProblemType: Bug
DistroRelease: Ubuntu 22.04
Package: cifs-utils 2:6.14-1ubuntu0.1
ProcVersionSignature: Ubuntu 5.15.0-67.74-generic 5.15.85
Uname: Linux 5.15.0-67-generic x86_64
ApportVersion: 2.20.11-0ubuntu82.3
Architecture: amd64
CasperMD5CheckResult: pass
Date: Sat Mar 18 17:59:38 2023
InstallationDate: Installed on 2023-03-09 (9 days ago)
InstallationMedia: Ubuntu-Server 22.04.2 LTS "Jammy Jellyfish" - Release amd64 (20230217.1)
ProcEnviron:
 SHELL=/bin/bash
 LANG=en_US.UTF-8
 TERM=xterm-256color
 PATH=(custom, no user)
SourcePackage: cifs-utils
UpgradeStatus: No upgrade log present (probably fresh install)

[Karl O. Pinc (kop)]

See also: bug #2012147
Here are clickable links for the bugs mentioned above: bug #2012140 bug #2012143