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Checking the Functionality

Reading and writing data to and from a dCache instance can be done with a number of protocols. After a standard installation, these protocols are dCap, GSIdCap, and GridFTP. In addition dCache comes with an implementation of the SRM protocol which negotiates the actual data transfer protocol.

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dCache without mounted namespace

Create the root of the Chimera namespace and a world-writable directory by

[root] # /usr/bin/chimera-cli mkdir /data
[root] # /usr/bin/chimera-cli mkdir /data/world-writable
[root] # /usr/bin/chimera-cli chmod /data/world-writable 777

To use WebDAV you need to define a WebDAV service in your layout file. You can define this service in an extra domain, e.g. [webdavDomain] or add it to another domain.

[webdavDomain]
[webdavDomain/webdav]
webdavAnonymousAccess=FULL

to the file /etc/dcache/layouts/mylayout.conf.

Note

Depending on the client you might need to set webdav.redirect.on-read=false and/or webdav.redirect.on-write=false.

#  ---- Whether to redirect GET requests to a pool
#
#   If true, WebDAV doors will respond with a 302 redirect pointing to
#   a pool holding the file. This requires that a pool can accept
#   incoming TCP connections and that the client follows the
#   redirect. If false, data is relayed through the door. The door
#   will establish a TCP connection to the pool.
#
(one-of?true|false)webdav.redirect.on-read=true

#  ---- Whether to redirect PUT requests to a pool
#
#   If true, WebDAV doors will respond with a 307 redirect pointing to
#   a pool to which to upload the file. This requires that a pool can
#   accept incoming TCP connections and that the client follows the
#   redirect. If false, data is relayed through the door. The door
#   will establish a TCP connection to the pool. Only clients that send
#   a Expect: 100-Continue header will be redirected - other requests
#   will always be proxied through the door.
#
(one-of?true|false)webdav.redirect.on-write=true

Now you can start the WebDAV domain

[root] # dcache start webdavDomain

and access your files via http://<webdav-door.example.org>:2880 with your browser.

You can connect the webdav server to your file manager and copy a file into your dCache.

To use curl to copy a file into your dCache you will need to set webdav.redirect.on-write=false.

Example:

Write the file test.txt

[root] # curl -T test.txt http://webdav-door.example.org:2880/data/world-writable/curl-testfile.txt

and read it

[root] # curl http://webdav-door.example.org:2880/data/world-writable/curl-testfile.txt

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Using dCache with a mounted filesystem

dCache can also be used with a mounted file system. Before mounting the name space you need to edit the /etc/exports file. Add the lines

/ localhost(rw)
/data

stop the portmapper

[root] # /etc/init.d/portmap stop
Stopping portmap: portmap

and restart dCache.

[root] # dcache restart

Now you can mount Chimera.

[root] # mount localhost:/ /mnt

With the root of the namespace mounted you can establish wormhole files so dCap clients can discover the dCap doors.

[root] # mkdir /mnt/admin/etc/config/dCache
[root] # touch /mnt/admin/etc/config/dCache/dcache.conf
[root] # touch /mnt/admin/etc/config/dCache/'.(fset)(dcache.conf)(io)(on)'
[root] # echo "<dcache.example.org>:22125" > /mnt/admin/etc/config/dCache/dcache.conf

Create the directory in which the users are going to store their data and change to this directory.

[root] # mkdir -p /mnt/data
[root] # cd /mnt/data

To be able to use dCap you need to have the dCap door running in a domain.

Example:

[dCacheDomain]
[dCacheDomain/dcap]

For this tutorial install dCap on your worker node. This can be the machine where your dCache is running.

Get the gLite repository (which contains dCap) and install dCap using yum.

[root] # cd /etc/yum.repos.d/
[root] # wget http://grid-deployment.web.cern.ch/grid-deployment/glite/repos/3.2/glite-UI.repo
[root] # yum install dcap

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dCap without mounted namespace

Create the root of the Chimera namespace and a world-writable directory for dCap to write into by

[root] # /usr/bin/chimera-cli mkdir /data
[root] # /usr/bin/chimera-cli mkdir /data/world-writable
[root] # /usr/bin/chimera-cli chmod /data/world-writable 777

Copy the data (here /bin/sh is used as example data) using the dccp command and the dCap protocol describing the location of the file using a URL, where <dcache.example.org> is the host on which the dCache is running

[root] # dccp -H /bin/sh dcap://<dcache.example.org>/data/world-writable/my-test-file-1
[##########################################################################################] 100% 718 kiB
735004 bytes (718 kiB) in 0 seconds

and copy the file back.

[root] # dccp -H dcap://<dcache.example.org>/data/world-writable/my-test-file-1 /tmp/mytestfile1
[##########################################################################################] 100% 718 kiB
735004 bytes (718 kiB) in 0 seconds

To remove the file you will need to mount the namespace.

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Using dCap with a mounted filesystem

dCap can also be used with a mounted file system. Before mounting the name space you need to edit the /etc/exports file. Add the lines

/ localhost(rw)
/data

stop the portmapper

[root] # /etc/init.d/portmap stop
Stopping portmap: portmap

and restart dCache.

[root] # dcache restart

Now you can mount Chimera.

[root] # mount localhost:/ /mnt

With the root of the namespace mounted you can establish wormhole files so dCap clients can discover the dCap doors.

[root] # mkdir /mnt/admin/etc/config/dCache
[root] # touch /mnt/admin/etc/config/dCache/dcache.conf
[root] # touch /mnt/admin/etc/config/dCache/'.(fset)(dcache.conf)(io)(on)'
[root] # echo "<dcache.example.org>:22125" > /mnt/admin/etc/config/dCache/dcache.conf

Create the directory in which the users are going to store their data and change to this directory.

[root] # mkdir -p /mnt/data
[root] # cd /mnt/data

Now you can copy a file into your dCache

[root] # dccp /bin/sh my-test-file-2
735004 bytes (718 kiB) in 0 seconds

and copy the data back using the dccp command.

[root] # dccp my-test-file-2 /tmp/mytestfile2
735004 bytes (718 kiB) in 0 seconds

The file has been transferred succesfully.

Now remove the file from the dCache.

[root] # rm  my-test-file-2