Currently there is unfortunately no official way to mirror the OS updates that the freebsd-update downloads, however we have just open sourced our tool, free for anyone to use!
See and get the tool on GitHub here: https://github.com/ateamsystems/freebsd-update-mirroring
This, in conjunction with a web server such as NginX, will allow you to locally mirror the update patch files used by the freebsd-update tool. This can be good for bandwidth conservation and for updating servers which have no direct internet connectivity.
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