If an rsync call gives you the following: buffer_append_space: alloc 10512504 not supported rsync: writefd_unbuffered failed to write 4092 bytes [sender]: Broken pipe (32) rsync: connection unexpectedly closed (36 bytes received so far) [sender] rsync error: unexplained error (code 255) at io.c(635) [sender=3.0.3] Don't bother to debug rsync! This is an SSH problem. You need to upgrade your SSH version (which is propably some 4.3 or older).