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.
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
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 stopStopping 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
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.
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 stopStopping 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-2735004 bytes (718 kiB) in 0 seconds
and copy the data back using the dccp command.
[root] #dccp my-test-file-2 /tmp/mytestfile2735004 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