The following example shows dccp being used to copy the file /etc/group into dCache as the the file /pnfs/example.org/data/dteam/test6. The dccp program will connect to dCache without authenticating.

[user] $ /opt/d-cache/dcap/bin/dccp /etc/group dcap://dcap-door.example.org:22125/pnfs/example.org/data/dteam/test6
Command failed!
Server error message for [1]: "path /pnfs/example.org/data/dteam/test6 not found" (errno 10001).
597 bytes in 0 seconds

The following example shows dccp being used to upload the file /etc/group. In this example, dccp will authenticate with dCache using the GSI protocol.

[user] $ /opt/d-cache/dcap/bin/dccp /etc/group gsidcap://gsidcap-door.example.org:22128/pnfs/example.org/data/dteam/test5
Command failed!
Server error message for [1]: "path /pnfs/example.org/data/dteam/test5 not found" (errno 10001).
597 bytes in 0 seconds

The following example shows dccp with the debugging enabled. The value 63 controls how much information is displayed.

[user] $ /opt/d-cache/dcap/bin/dccp -d 63   /etc/group dcap://dcap-door.example.org:22128/pnfs/example.org/data/dteam/test3
Dcap Version version-1-2-42 Jul 10 2007 19:56:02
Using system native stat64 for /etc/group.
Allocated message queues 0, used 0

Using environment variable as configuration
Allocated message queues 1, used 1

Creating a new control connection to dcap-door.example.org:22128.
Activating IO tunnel. Provider: [libgsiTunnel.so].
Added IO tunneling plugin libgsiTunnel.so for dcap-door.example.org:22128.
Setting IO timeout to 20 seconds.
Connected in 0.00s.
Removing IO timeout handler.
Sending control message: 0 0 client hello 0 0 2 42 -uid=501 -pid=32253 -gid=501
Server reply: welcome.
dcap_pool:  POLLIN on control line [3] id=1
Connected to dcap-door.example.org:22128
Sending control message: 1 0 client stat "dcap://dcap-door.example.org:22128/pnfs/example.org/data/dteam/test3" -uid=501
Command failed!
Server error message for [1]: "path //pnfs/example.org/data/dteam/test3 not found" (errno 10001).
[-1] unpluging node
Removing unneeded queue [1]
[-1] destroing node
Real file name: /etc/group.
Using system native open for /etc/group.
extra option:  -alloc-size=597
[Fri Sep  7 17:50:56 2007] Going to open file dcap://dcap-door.example.org:22128/pnfs/example.org/data/dteam/test3 in cache.
Allocated message queues 2, used 1

Using environment variable as configuration
Activating IO tunnel. Provider: [libgsiTunnel.so].
Added IO tunneling plugin libgsiTunnel.so for dcap-door.example.org:22128.
Using existing control connection to dcap-door.example.org:22128.
Setting hostname to dcap-door.example.org.
Sending control message: 2 0 client open "dcap://dcap-door.example.org:22128/pnfs/example.org/data/dteam/test3" w -mode=0644 -truncate dcap-door.example.org 33122 -timeout=-
1 -onerror=default  -alloc-size=597  -uid=501
Polling data for destination[6] queueID[2].
Got callback connection from dcap-door.example.org:35905 for session 2, myID 2.
cache_open -> OK
Enabling checksumming on write.
Cache open succeeded in 0.62s.
[7] Sending IOCMD_WRITE.
Entered sendDataMessage.
Polling data for destination[7] queueID[2].
[7] Got reply 4x12 bytes len.
[7] Reply: code[6] response[1] result[0].
get_reply: no special fields defined for that type of response.
[7] Got reply 4x12 bytes len.
[7] Reply: code[7] response[1] result[0].
get_reply: no special fields defined for that type of response.
[7] Expected position: 597 @ 597 bytes written.
Using system native close for [5].
[7] unpluging node
File checksum is: 460898156
Sending CLOSE for fd:7 ID:2.
Setting IO timeout to 300 seconds.
Entered sendDataMessage.
Polling data for destination[7] queueID[2].
[7] Got reply 4x12 bytes len.
[7] Reply: code[6] response[4] result[0].
get_reply: no special fields defined for that type of response.
Server reply: ok destination [2].
Removing IO timeout handler.
Removing unneeded queue [2]
[7] destroing node
597 bytes in 0 seconds
Debugging

[user] $ export
DCACHE_IO_TUNNEL=/opt/d-cache/dcap/lib/libgsiTunnel.so

dCap is a POSIX like interface for accessing dCache, allowing unmodified applications to access dCache transparently. This access method uses a proprietary data transfer protocol, which can emulate POSIX access across the LAN or WAN.

Unfortunately the client requires inbound connectivity and so it is not practical to use this protocol over the WAN as most sites will not allow inbound connectivity to worker nodes.

To make non dCache aware applications access files within dCache through dCap all that is needed is set the LD_PRELOAD environment variable to /opt/d-cache/dcap/lib/libpdcap.so.

[user] $ export LD_PRELOAD=/opt/d-cache/dcap/lib/libpdcap.so

Setting the LD_PRELOAD environment variable results in the library libpdcap.so overriding the operating system calls. After setting this environment variable, the standard shell command should work with dCap and GSIdCap URLs.

[user] $ cp /etc/group gsidcap://gsidcap-door.example.org:22128/pnfs/example.org/data/dteam/myFile
[user] $ ls gsidcap://gsidcap-door.example.org:22128/pnfs/example.org/data/dteam/DirOrFile
[user] $ head -3 gsidcap://gsidcap-door.example.org:22128/pnfs/example.org/data/dteam/myFile
root:x:0:
daemon:x:1:
bin:x:2:
[user] $ rm gsidcap://gsidcap-door.example.org:22128/pnfs/example.org/data/dteam/MyFile