wiki:Installation of dCache server
Last modified 7 years ago Last modified on 06/05/13 18:07:41
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Installation of dCache server


In this part we install dCache as a single node instance. Which means that all our services will run on the same host, it shows us the basics and necessary setup. At the end of this part we will have a running dCache that can be mounted locally as well as on your client.

  1. Find the dCache server rpm on your server in the root's home direcrory /root/:
[root]# ls dcache-*

If you are using your own virtual machine, please download the rpm from dCache Downloads

  1. Install the rpm on your server machine:
[root]# rpm -ivh dcache-2.6.0-1.noarch.rpm
Preparing...                ########################################### [100%]

1:dcache                 ########################################### [100%]

dCache server has three dependencies: java-1.7.0-openjdk, postgresql-server (version >8.4) and nfs-utils. You will find that openjdk, postgresql-server and nfs-utils are already installed on your machine. Run the following command to check for the java, postgresql and nfs-utils packages.

[root]# rpm -qa |grep -E "postgresql92-server|java-1.7.0-openjdk|nfs-utils"

Look this up later: For more information on this please see dCache Book - Prerequisites. There are also several trivial steps that you have to do to setup postgresql, but they are not part of this tutorial and can be found in dCache Book - Readying the PostgreSQL server for the use with dCache We don't focus on detailed configuration of postgres server here, but have a look at the provided script for the commands needed if you are interested (

[root]# cat
/etc/init.d/postgresql-9.2 status -D /var/lib/postgres/data >/dev/null 2>&1
if [ $rtn -ne 0 ]; then
  echo "not running"
  echo "Postgres running. Stopping Postgres"
  /etc/init.d/postgresql-9.2 stop

if [ -d /var/lib/pgsql/9.2/data ]
  rm -rf /var/lib/pgsql/9.2/data/
  echo "/var/lib/pgsql/9.2/data/ deleted"

service postgresql-9.2 initdb
sed -ie 's/max_connections = 100/max_connections = 1000/' /var/lib/pgsql/9.2/data/postgresql.conf
service postgresql-9.2 start
chkconfig postgresql-9.2 on

mv /var/lib/pgsql/9.2/data/pg_hba.conf{,_ori}
cat >/var/lib/pgsql/9.2/data/pg_hba.conf <<EOF

# "local" is for Unix domain socket connections only
local all all trust
# IPv4 local connections:
host all all trust
# IPv6 local connections:
host all all ::1/128 trust
service postgresql-9.2 restart
createdb -U postgres chimera
createuser -U postgres --no-superuser --no-createrole --createdb chimera
createuser -U postgres --no-superuser --no-createrole --createdb srmdcache
createdb -U srmdcache dcache
createdb -O srmdcache -U postgres billing

Now execute the script:

[root]# ./
Initializing database:                                     [  OK  ]
Starting postgresql-9.2 service:                           [  OK  ]
Stopping postgresql-9.2 service:                           [  OK  ]
Starting postgresql-9.2 service:                           [  OK  ]

Now you have a running and fully configured postgresql server and installed dCache server.

Configuration files

We make use of flat files, to define and change the settings for the layout and the behavior of dCache on different levels (per host, per domain or per service). There are three main places for the configuration files:

  • /usr/share/dcache/defaults

This directory is filled with files defining the default settings for all dCache services, as they are shipped by Do not modify these files, as they will be replaced by subsequent updates!

  • /etc/dcache/dcache.conf

The central configuration file, that ideally should be nearly identical on all nodes of the dCache setup. Maybe it is possible to have only one difference among all nodes at all: the parameter pointing to the layout configuration files. To get to know what settings can be made in dcache.conf you can look through in the defaults directory.

  • /etc/dcache/layouts

Layout files are the place to define the actual topology for the dCache services/domains on this node. So typically no layout file of one node is identical to any other layout file of another node in the setup. provides us with premade layout files that state a possible distribution of services over domains: head.conf, pool.conf and single.conf. Right now you could start dCache and it would use the empty dcache.conf file and the fallback layout file single.conf. With this the most important core services will be configured to run in one single domain with default settings. Alternatively, head.conf has predefined the mandatory services in a decent number of domains to be run on the headnode of your setup. Of course, you will need at least one other node using pool.conf to provide some disk space to dCache.

We would like to have our own layout file that we just use for this hands-on, therefor we create it from a template:

[root]# cp /etc/dcache/layouts/{single,berlin2013_ws}.conf 

We need to tell dCache to use the layout file we just created and add this to /etc/dcache/dcache.conf. Do not make the mistake of entering the entire file name there, just add the following line:


Adjust the layout file

Firstly we need to tell dCache that there will be many domains communicating with each other:

[root]# vi /etc/dcache/layouts/berlin2013_ws.conf

As we described in the introduction dCache services run inside so called domains. Since we will have many domains, we will need some mechanism for these domains to communicate. The cells framework is used for this communication, which is why we activate it by adding the following line to the beginning of /etc/dcache/layouts/berlin2013_ws.conf:


As mentioned we want to be able to mount dCache locally using NFSv41. Therefor a service called nfsv41 needs to be started, which we will keep in a separate domain for convenience of restarting it separately from the rest of dCache. These lines need to be added at the end of /etc/dcache/layouts/berlin2013_ws.conf. They add a domain to dCache - [nfs-Domain] - that holds the nfsv41 service.


Then leave the file after saving it, make sure you are not in INSERT mode by pressing ESC. Then type:


(Just for the ones not familiar with vi.)

Before we can start dCache we have to empty /etc/dcache/gplazma.conf as there is no security configured in a blank dCache:

[root]# echo "" > /etc/dcache/gplazma.conf

Check that all is done properly before starting dcache:

[root]# dcache check-config
No problems found.

Now start dCache by:

[root]# dcache start
Starting dCacheDomain done
Starting nfs-Domain done

Check if dCache has started up correctly for domains:

[root]# dcache status
dCacheDomain running 18314 dcache
nfs-Domain   running 18359 dcache

and services:

[root]# dcache services
DOMAIN       SERVICE         CELL            LOG
dCacheDomain admin           alm             /var/log/dcache/dCacheDomain.log
dCacheDomain broadcast       broadcast       /var/log/dcache/dCacheDomain.log
dCacheDomain poolmanager     PoolManager     /var/log/dcache/dCacheDomain.log
dCacheDomain loginbroker     LoginBroker     /var/log/dcache/dCacheDomain.log
dCacheDomain spacemanager    SrmSpaceManager /var/log/dcache/dCacheDomain.log
dCacheDomain pnfsmanager     PnfsManager     /var/log/dcache/dCacheDomain.log
dCacheDomain cleaner         cleaner         /var/log/dcache/dCacheDomain.log
dCacheDomain dir             dirLookupPool   /var/log/dcache/dCacheDomain.log
dCacheDomain gplazma         gPlazma         /var/log/dcache/dCacheDomain.log
dCacheDomain pinmanager      PinManager      /var/log/dcache/dCacheDomain.log
dCacheDomain billing         billing         /var/log/dcache/dCacheDomain.log
dCacheDomain srm-loginbroker srm-LoginBroker /var/log/dcache/dCacheDomain.log
dCacheDomain httpd           httpd           /var/log/dcache/dCacheDomain.log
dCacheDomain topo            topo            /var/log/dcache/dCacheDomain.log
dCacheDomain info            info            /var/log/dcache/dCacheDomain.log
nfs-Domain   nfsv41          NFSv41-vt-021   /var/log/dcache/nfs-Domain.log

Then also check the log files:

[root@vt-021 data]# tail -F /var/log/dcache/*
==> /var/log/dcache/dCacheDomain.log <==
01 Mar 2013 18:22:01 (gPlazma) [] NodeList has 1 entries
01 Mar 2013 18:22:01 (gPlazma) [] examining plugin with class class org.dcache.gplazma.plugins.JaasPlugin
01 Mar 2013 18:22:01 (gPlazma) [] Adding plugin [jaas, org.dcache.gplazma.plugins.JaasPlugin]
01 Mar 2013 18:22:01 (gPlazma) [] Created 1 plugin metadata entries
01 Mar 2013 18:22:03 (PinManager) [] [AspectJ] javax.* types are not being woven because the weaver option '-Xset:weaveJavaxPackages=true' has not been specified
INFO 3/1/13 6:22 PM:liquibase: Successfully acquired change log lock
INFO 3/1/13 6:22 PM:liquibase: Reading from databasechangelog
INFO 3/1/13 6:22 PM:liquibase: Reading from databasechangelog
INFO 3/1/13 6:22 PM:liquibase: Successfully released change log lock
INFO 3/1/13 6:22 PM:liquibase: Successfully released change log lock

==> /var/log/dcache/nfs-Domain.log <==

2013-03-01 18:21:52 Launching /usr/bin/java -server -Xmx512m -XX:MaxDirectMemorySize=512m -Dorg.globus.tcp.port.range=20000,25000 -Dorg.dcache.dcap.port=0 -Dorg.globus.jglobus.delegation.cache.lifetime=30000 -Dorg.globus.jglobus.crl.cache.lifetime=60000 -Djava.awt.headless=true -DwantLog4jSetup=n -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/log/dcache/nfs-Domain-oom.hprof -javaagent:/usr/share/dcache/classes/spring-instrument-3.1.1.RELEASE.jar -Ddcache.home=/usr/share/dcache -Ddcache.paths.defaults=/usr/share/dcache/defaults org.dcache.boot.BootLoader start nfs-Domain
01 Mar 2013 18:21:54 (System) [] Created : nfs-Domain

Now exit the tail command by pressing control+c.

This should show you that domains were created and no error messages should be flying around, so the output that tail shows should stop at some point after starting dCache although some output is normal to inform about successful domain creation.

First Contact

Now that we have a running dCache that does nothing we would like to make a first contact. This will be achieved by mounting dCache locally via NFSv41.

dCache needs several things to come together to be able to store data in it. It needs to authenticate and authorize people wanting to store data (gPlazma takes care of this), it needs a logical structure where file's names can be found in a directory structure, the namespace, which keeps file's meta data. The actual files are stored in a service that is called a pool that allows writing data to block devices and allows for a hierarchical storage management to be employed (More about this in the tertiary storage part of this hands-on).

dCache needs something that holds that actual data, the pools. So we first create a pool that is stored in a certain path in the local file system and set its maximum size. Execute the following command in your server console:

[root]# dcache pool create --size=419430400  --meta=db --lfs=precious   /pools/nfsPool nfsPool poolDomain
Created a pool in /pools/nfsPool. The pool was added to poolDomain in

After we created the pool we need to start the domain that was created by executing:

[root]# dcache status
dCacheDomain running 22269 dcache
nfs-Domain   running 22313 dcache
poolDomain   stopped       dcache
[root]# dcache start poolDomain
Starting poolDomain done

The pool service will always make sure that there is enough space on the pool to allow for some data to be moved around. The amount of space that is kept free is configurable and by default it is 4 GiB. For this tutorial we need to set the gap to a very low value (10 MB) because the disk space on the hands-on machines is so limited. In order to be able to administrate dCache we need to login to the admin interface. We will be login in key-based with ssh2. Please create yourself a DSA key and store the public key in /etc/dcache/admin/authorized_keys2. Do the following steps to change the gap size:

[root]# ssh-keygen -t dsa
[root]# cat .ssh/ > /etc/dcache/admin/authorized_keys2
[root]# ssh -l admin -p 22224 localhost
... (local) admin > cd nfsPool
... (nfsPool) admin > set gap 10m
Gap set to 10485760
... (nfsPool) admin > save

Then exit the admin interface by pressing control+d. This now enables us to actually store files in dCache, but how? ... for example via a mounted NFSv41.

We need to set the NFS domain to make sure nfs server and client are inside the same namespace. This is done by adding the following line to the end of /etc/dcache/dcache.conf:

nfs.domain = berlin-domain

As mentioned dCache also needs a namespace where file's meta data is stored. We need to create a directory in the dCache namespace by executing:

[root]# chimera-cli mkdir /data
[root]# chimera-cli mkdir /data/world-writable

We do not have authentication setup yet, which is why we need to set the directory world writable to be able to write:

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

We also need to tell the nfs server that machines are allowed to mount certain directories that the dCache server provides access to. This is not really a dCache specific thing as you would also use the /etc/exports file for a non-dCache nfs servers. Please add the following line to /etc/exports:

/data localhost(rw)

This states that the directory /data can be accessed by localhost with read/write permissions. Now we will be able to see the benefit of having the nfsv41 service in a separate domain as we need to restart the domain for the change in /etc/exports to take effect.

[root]# dcache status
dCacheDomain running 26853 dcache 
nfs-Domain   running 26903 dcache 
poolDomain   running 26959 dcache 

[root]# dcache restart nfs-Domain
Stopping nfs-Domain 0 1 2 done
Starting nfs-Domain done

Had we not had the nfsv41 service running in a separate domain we would have had to restart entire dCache, which can be very bad when you want to maintain a production dCache in service.

After this we can mount dCache locally by doing the following:

[root]# mkdir /nfs4
[root]# mount -o intr,minorversion=1 localhost:/data /nfs4

Now you can copy some file e.g.:

[root]# cp /etc/hosts /nfs4/world-writable/myFirstNfsFile00001

Congratulations you wrote your first file into dCache. We will now mount nfsv41 on the client. Therefor we need to grant it permission on the server side. Therefore edit /etc/exports:

[root]# vi /etc/exports

and change the one line from

/data localhost(rw)


/data localhost(rw) <your client IP address>(rw)

then exit INSERT mode and save. This line now means that directory /data can be mounted with read-write permissions from localhost as well as <your client address>. After addition of this permission restart dCache:

[root]# dcache restart

Now go to your client:


There you can have a look at:

[root]# less /etc/idmapd.conf

At the top of this file you will find:

#Verbosity = 0
# The following should be set to the local NFSv4 domain name
# The default is the host's DNS domain name.
Domain = berlin-domain

Remember, earlier we set the nfs.domain = berlin-domain in the dcache.conf on the server. This is now telling server and client to be in the same domain. If you had to change this value, which we luckily already did for you, you would have to restart the /etc/rpcidmapd service. But that is not necessary, now. You will also find that your client machine has a /nfs4 directory, which we created, so that all that is left for you to do is to mount and have a look at the mounted dCache and unmount:

[root]# mount -o intr,minorversion=1 <your server address>:/data /nfs4
[root]# ls /nfs4
[root]# umount /nfs4

Please note: For the nfsv41 mount to work on our client we need a nfs-utils installed, an SL6 kernel > 2.6.32-220.

What you have now is a running dCache server that has a mounted NFSv41 server locally that you have access data without any authentication. In this section we also created started a pool service with one pool, we created a directory /data that holds our data and a subdirectory /data/world-writable that can be used without authentication.

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