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Only content that is added or changed while the Serializer is running will be copied to /tmp/descriptions and /tmp/binaries.
An Example
Following the instructions above, I created a new empty 4.6.0 Fedora repository.
I then created a new container (via the web interface) at http://localhost:8080/fcrepo/rest/album
Inside that container I uploaded a binary file, without specifying an identifier (i.e. let Fedora auto-generate an identifier). This resulted in a binary file at http://localhost:8080/fcrepo/rest/album/ea/50/12/93/ea501293-64bf-430e-bf97-abcd64fda0c4 (the identifier will be different for you if you reproduce these steps).
Next, I looked in /tmp/descriptions and /tmp/binaries and found output that was generated by the Camel Serializer
Sample Output
The metadata for the album container I created at http://localhost:8080/fcrepo/rest/album was saved to a turtle file at /tmp/descriptions/albums.ttl.
The metadata for the jpg binary file I uploaded to http://localhost:8080/fcrepo/rest/album/ea/50/12/93/ea501293-64bf-430e-bf97-abcd64fda0c4 was saved to a turtle file at /tmp/descriptions/albums/ea/50/12/93/ea501293-64bf-430e-bf97-abcd64fda0c4.ttl.
The jpg file was saved as a binary at /tmp/binaries/albums/ea/50/12/93/ea501293-64bf-430e-bf97-abcd64fda0c4 .
I manually confirmed that the md5sum of this binary in /tmp/binaries matched the original files checksum.
There are additional ttl files in /tmp/descriptions/fedora:system that contain Fedora generated triples, as well as 2 binaries in /tmp/binaries/fedora:system, which I ignored as they are not part of the Resource I am interested in serializing in this test.
vagrant@fedora4:/tmp$ tree descriptions/
descriptions/
├── albums
│ └── ea
│ └── 50
│ └── 12
│ └── 93
│ └── ea501293-64bf-430e-bf97-abcd64fda0c4.ttl
├── albums.ttl
└── fedora:system
├── fedora:transform
│ └── fedora:ldpath
│ ├── default
│ │ └── fedora:Resource.ttl
│ ├── default.ttl
│ ├── deluxe
│ │ └── fedora:Resource.ttl
│ └── deluxe.ttl
└── fedora:transform.ttl
vagrant@fedora4:/tmp$ tree binaries/
binaries/
├── albums
│ └── ea
│ └── 50
│ └── 12
│ └── 93
│ └── ea501293-64bf-430e-bf97-abcd64fda0c4
└── fedora:system
└── fedora:transform
└── fedora:ldpath
├── default
│ └── fedora:Resource
└── deluxe
└── fedora:Resource
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