[Samba] Occasional "Permission denied" errors when installing R packages onto a share

[Heckmann, Ilja]

Hello,

When trying to store a user's personal R library on an SMB share (so that users
without admin rights can have their personal libraries accessible from several
compute servers), some packages fail to install with a "Permission denied" error
from "mv", while others install without problems. We have run out of our own
ideas on how to fix this and would appreciate any help.

The user library by default is located under
"~/R/${SYSTEM_INFO}-library/${R_VERSION}/". R's installation procedure runs
somewhat like this:

1. A subfolder named "00LOCK-${PKG_NAME}/00new/${PKG_NAME}" is created inside
   the library folder.
2. Library binaries are compiled.
3. HTML documentation is created.
4. The folder "${PKG_NAME}" is moved up two levels.
5. The "00LOCK..." folder is removed.

Step 4 fails reproducibly for some packages, while succeeding for others. Here is
a reproduction procedure in a Fedora 38 VM:

1. Install Fedora 38 Workstation (Fedora-Workstation-Live-x86_64-38-1.6.iso).
   Username: 'user'
2. Disable SELinux (edit /etc/selinux/config and set "SELINUX=disabled") and
   reboot. Alternatively set up SELinux as described here:
   <https://docs.fedoraproject.org/en-US/quick-docs/samba/>
3. Set up and mount a basic Samba share:

   $ sudo dnf install samba
   $ sudo cat << 'EOF' >> /etc/samba/smb.conf
   [share]
     path = /home/user/share
     writable = yes
     valid users = user
   EOF
   $ sudo smbpasswd -a user
   $ mkdir /home/user/{share,R}
   $ sudo systemctl restart smb
   $ sudo mount -t cifs //localhost/share /home/user/R -o username=user,uid=user

4. Install R:

   $ sudo dnf install R

5. Start R (command line arguments are optional) and install the package "xml2":

   $ R --quiet --no-save
   > install.packages('xml2', repos='https://cloud.r-project.org')

   Confirm twice when asked about the personal library. This will only be needed
   on the first attempt to install a package.
6. The installation should fail with this message:

   mv: cannot move '/home/user/R/x86_64-redhat-linux-gnu-library/4.3/00LOCK-xml2/00new/xml2'
   to '/home/user/R/x86_64-redhat-linux-gnu-library/4.3/xml2': Permission denied
   ERROR:   moving to final location failed

Executing the same "mv" command manually in the shell after closing R succeeds
however, and as far as I understand, all R is doing is calling out to "mv": the
corresponding code is in <https://svn.r-project.org/R/trunk/src/library/tools/R/install.R>,
Ctrl+F "moving to final location", second match.

Two counterexamples of when the installation succeeds: installing the package
"rlang" and the same package "xml2" but without the documentation:

$ R --quiet --no-save
> install.packages('rlang', repos='https://cloud.r-project.org')
> install.packages('xml2', repos='https://cloud.r-project.org', INSTALL_opts='--no-help')

We also tried different servers to figure out whether the problem is with the
server or the client, and these are the findings:

- Samba: fails as described above
- Windows 8: fails as described above
- NetApp: succeeds

This to me rules out a client-side problem with "mount.cifs" since the NetApp
setup works without problems. Since both Windows and Samba fail in the same way,
Samba seems to properly emulate the behavior of a Windows machine, so it
doesn't look like a bug in Samba but rather the expected behavior. So the
question is: Is there a way to configure the server so that this operation
succeeds?

Samba versions tested: 4.10.16 on CentOS 7, 4.17.5 on AlmaLinux 8.8, 4.18.3 on
Fedora 38.

Thank you,
Ilja