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Mounting Chimera through NFS
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The dCache Book > Configuration of dCache > Chimera > Mounting Chimera through NFS

Mounting Chimera through NFS

dCache does not need the Chimera filesystem to be mounted but a mounted file system is convenient for administrative access. This offers the opportunity to use OS-level tools like ls and mkdir for Chimera. However, direct I/O-operations like cp are not possible, since the NFSv3 interface provides the namespace part only. This section describes how to start the Chimera NFSv3 server and mount the name space.

If you want to mount Chimera for easier administrative access, you need to edit the /etc/exports file as the Chimera NFS server uses it to manage exports. If this file doesn’t exist it must be created. The typical exports file looks like this: 

/ localhost(rw)
/data
# or
# /data *.my.domain(rw)

As any RPC service Chimera NFS requires rpcbind service to run on the host. Nevertheless rpcbind has to be configured to accept requests from Chimera NFS.

On RHEL6 based systems you need to add 

RPCBIND_ARGS="-i"

into /etc/sysconfig/rpcbind and restart rpcbind. Check your OS manual for details. 

[root] # service rpcbind restart
Stopping rpcbind:                                          [  OK  ]
Starting rpcbind:                                          [  OK  ]

If your OS does not provide rpcbind Chimera NFS can use an embedded rpcbind. This requires to disable the portmap service if it exists. 

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

and restart the domain in which the NFS server is running.

Example:

[root] # dcache restart namespaceDomain

Now you can mount Chimera by 

[root] # mount localhost:/ /mnt

and create the root of the Chimera namespace which you can call data: 

[root] # mkdir -p /mnt/data

If you don’t want to mount chimera you can create the root of the Chimera namespace by 

[root] # /usr/bin/chimera mkdir /data

You can now add directory tags. For more information on tags see the section called “Directory Tags”. 

[root] # /usr/bin/chimera writetag /data sGroup "chimera"
[root] # /usr/bin/chimera writetag /data OSMTemplate "StoreName sql"

[return to top]

Using dCap with a mounted file system

If you plan to use dCap with a mounted file system instead of the URL-syntax (e.g. dccp /data/file1 /tmp/file1), you need to mount the root of Chimera locally (remote mounts are not allowed yet). This will allow us to establish wormhole files so dCap clients can discover the dCap doors. 

[root] # mount localhost:/ /mnt
[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 "<door host>:<port>" > /mnt/admin/etc/config/dCache/dcache.conf

The default values for ports can be found in Chapter 29, dCache Default Port Values (for dCap the default port is 22125) and in the file /usr/share/dcache/defaults/dcache.properties. They can be altered in /etc/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 test-file
735004 bytes (718 kiB) in 0 seconds

and copy the data back using the dccp command. 

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

The file has been transferred succesfully.

Now remove the file from the dCache. 

[root] # rm  test-file

When the configuration is complete you can unmount Chimera: 

[root] # umount /mnt

Note

Please note that whenever you need to change the configuration, you have to remount the root localhost:/ to a temporary location like /mnt.

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