ret = WIMLIB_ERR_WRITE;
if (unlikely(write_flags & WIMLIB_WRITE_FLAG_UNSAFE_COMPACT)) {
/* Truncate any data the compaction freed up. */
- if (ftruncate(wim->out_fd.fd, wim->out_fd.offset)) {
+ if (ftruncate(wim->out_fd.fd, wim->out_fd.offset) &&
+ errno != EINVAL) /* allow compaction on untruncatable files,
+ e.g. block devices */
+ {
ERROR_WITH_ERRNO("Failed to truncate the output WIM file");
goto out;
}