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In my case, trying to install the Guest Additions on a headless Fedora server failed with /var/log/vboxadd-setup.log containing only the line Could not find the X.Org or XFree86 Window System, skipping. Note the build process can output multiple log files, which means looking at only the latest one (as the message it outputs suggests) is not a reliable way of diagnosing problems. Static void sf_ftime_from_timespec(struct timespec *tv, RTTIMESPEC *ts) tmp/vbox.0/utils.c:53:53: note: expected ‘struct timespec *’ but argument is of type ‘struct timespec64 *’ Sf_ftime_from_timespec(&inode->i_atime, &info->AccessTime) tmp/vbox.0/utils.c:165:28: error: passing argument 1 of ‘sf_ftime_from_timespec’ from incompatible pointer type The symptom is messages like these appearing in one of the log files written to /var/log by the build process: /tmp/vbox.0/utils.c: In function ‘sf_init_inode’:
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The solution (for now) is to download and install the latest development snapshot of the Guest Additions, version 5.2.97, as explained in a ticket on the VirtualBox site.
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A similar problem can occur with VirtualBox 5.2.18 and Linux guests, including Fedora 28, that are running kernel 4.18: Building the Guest Additions will fail with the same error message, “modprobe vboxsf failed”, and no vboxsf module output to the /lib/modules folder.
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