Fix "make install" with DESTDIR set

[kohlschuetter]

"DESTDIR=/path/to/target/root/ make install" may fail when installing to a root that contains an existing lib/modules structure. When run as root we may even affect the wrong kernel (the build system's one, or, if running a different version, some other directory in /lib/modules, but not the desired one installed in DESTDIR).

Add a missing reference to the INSTALL_MOD_PATH root when calling "depmod" during "make install"

Also add a switch "DONT_DELETE_MODULES_FILES=1" that skips the removal of files named "modules.*" prior to running depmod.

Signed-off-by: Christian Kohlschütter [email protected]
Closes #16994

Motivation and Context

Fixes an important build issue when installing to DESTDIR.
see issue #16994

Description

In addition to the details in #16994:

I'm sure there's a reason why the current makefile deletes files starting with "modules.*", so I'm only adding a switch that can disable that functionality when not desired.

With this change, I can now install zfs nto my target root as follows:

DONT_DELETE_MODULES_FILES=1 DESTDIR=/tmp/kernel-out make install

How Has This Been Tested?

Tested on Alpine Linux 3.21.2 using the following zfs build instructions

#KERNEL_DIR=/path/to/kernel/source
#KERNEL_OUT=/path/to/target/root
./configure --prefix=/usr \
			--with-tirpc \
			--sysconfdir=/etc \
			--mandir=/usr/share/man \
			--infodir=/usr/share/info \
			--localstatedir=/var \
			--with-config=kernel \
			--with-linux="$KERNEL_DIR"
make -s -j$(nproc)
DONT_DELETE_MODULES_FILES=1 DESTDIR="$KERNEL_OUT" make install

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied. (NOTE: unrelated since it's an integration issue)
• All commit messages are properly formatted and contain Signed-off-by.

[robn]

Nice. I've had a similar workaround (the -b part) for over a year for my local dev VMs. I have no opinion on the "don't delete" flag other than its useful and nonintrusive.