Sendfile does not work on Live CDs

Kent Spillner
and I were trying to set up an Ubuntu Live CD with a full rails stack
running our current project. We were seeing weird issues with
nginx, such as connections being
unexpectedly terminated and file uploads not working.

We asked around and Chris Read pointed out
that Live CDs use the UnionFS filesystem which does not support

From the Versatility and Unix Semantics in Namespace


”…the sendfile system call requires a matching file structure and
address space structure. As Unionfs presently has no address space
structure, we cannot properly implement sendfile, which is required for
loop device mounts and improves performance for Web and NFS servers.”

Once we turned off sendfile
(, everything
worked perfectly.

Paul Gross

Paul Gross

I'm a lead software developer in Seattle working for Braintree Payments.

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