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Install XRootD Standalone

XRootD is a hierarchical storage system that can be used in a variety of ways to access data, typically distributed among actual storage resources. In this document we focus on using XRootD as a simple layer exporting an underlying storage system (e.g., HDFS) to the outside world.

Note

The OSG only supports XRootD standalone installations on EL7 hosts

Before Starting

Before starting the installation process, consider the following points:

• User IDs: If it does not exist already, the installation will create the Linux user ID xrootd
• Service certificate: The XRootD service uses a host certificate and key pair at /etc/grid-security/xrd/xrdcert.pem and /etc/grid-security/xrd/xrdkey.pem
• Networking: The XRootD service uses port 1094 by default

As with all OSG software installations, there are some one-time (per host) steps to prepare in advance:

• Ensure the host has a supported operating system
• Obtain root access to the host
• Prepare the required Yum repositories
• Install CA certificates

Installing XRootD

To install XRootD, run the following Yum command:

[email protected] # yum install xrootd

Configuring XRootD

To configure XRootD as a standalone server, replace the contents of /etc/xrootd/xrootd-standalone.cfg as follows:

1. Add an all.export directive for each directory that you wish to serve via XRootD. For example, to serve the contents of /store and /public:

   all.export /store/
   all.export /public/
   

   Note

   The directories specified this way are writable by default. Access controls should be managed via authorization configuration.

2. Add an all.sitename directive set to the resource name of your XRootD service. For example, the XRootD service registered at the FermiGrid site should set the following configuration:

   all.sitename   Fermilab Public DCache
   

   Note

   CMS sites should follow CMS policy for all.sitename

3. Append the following configuration to the end of /etc/xrootd/xrootd-standalone.cfg

   xrd.port 1094
   all.role server
   
   cms.allow host *
   # Logging verbosity
   xrootd.trace emsg login stall redirect
   ofs.trace -all
   xrd.trace conn
   cms.trace all
   
   xrd.report xrd-report.osgstorage.org:9931
   xrootd.monitor all \
                  auth \
                  flush 30s \
                  window 5s fstat 60 lfn ops xfr 5 \
                  dest redir fstat info user xrd-report.osgstorage.org:9930 \
                  dest fstat info user xrd-mon.osgstorage.org:9930
   
   xrd.network keepalive kaparms 10m,1m,5
   xrd.timeout idle 60m
   

Configuring authorization

To configure XRootD authorization please follow the documentation here.

Optional configuration

The following configuration steps are optional and will likely not be required for setting up a small site. If you do not need any of the following special configurations, skip to the section on using XRootD.

Enabling HTTP support

In order to enable XRootD HTTP support please follow the instructions here

Enabling Hadoop support

For documentation on how to export your Hadoop storage using XRootD please see this documentation

Enabling CMS TFC support (CMS sites only)

For CMS users, there is a package available to integrate rule-based name lookup using a storage.xml file. See this documentation.

Using XRootD

In addition to the XRootD service itself, there are a number of supporting services in your installation. The specific services are:

Software	Service Name	Notes
Fetch CRL	fetch-crl-boot and fetch-crl-cron	See CA documentation for more info
XRootD	[email protected]

Start the services in the order listed and stop them in reverse order. As a reminder, here are common service commands (all run as root):

To …	On EL 7, run the command…
Start a service	systemctl start SERVICE-NAME
Stop a service	systemctl stop SERVICE-NAME
Enable a service to start during boot	systemctl enable SERVICE-NAME
Disable a service from starting during boot	systemctl disable SERVICE-NAME

Validating XRootD

To validate an XRootD installation, perform the following verification steps:

1. Verify file transfer over the XRootD protocol using XRootD client tools:

   1. Install the client tools:

      [email protected] # yum install xrootd-client
      

   2. Copy a file to a directory for which you have write access:

      [email protected] # xrdcp /bin/sh root://localhost:1094//tmp/first_test
      [xrootd] Total 0.76 MB  [====================] 100.00 % [inf MB/s]
      

   3. Verify that the file has been copied over:

      [email protected] # ls -l /tmp/first_test
      -rw-r--r-- 1 xrootd xrootd 801512 Apr 11 10:48 /tmp/first_test
      

2. If you have enabled HTTP support, verify file transfer over HTTP using GFAL2 client tools:

   1. Install the GFAL2 client tools:

      [email protected] # yum install gfal2-util gfal2-plugin-http
      

   2. Copy a file to a directory for which you have write access:

      [email protected] # gfal-copy /bin/sh http://localhost:1094//tmp/first_test
      

   3. Verify that the file has been copied over:

      [email protected] # ls -l /tmp/first_test
      -rw-r--r-- 1 xrootd xrootd 801512 Apr 11 10:48 /tmp/first_test
      

Getting Help

To get assistance. please use the Help Procedure page.

Reference

• XRootD documentation
• Export directive in the XRootD configuration and relevant options

File locations

Service/Process	Configuration File	Description
xrootd	/etc/xrootd/xrootd-standalone.cfg	Main XRootD configuration
	/etc/xrootd/auth_file	Authorized users file

Service/Process	Log File	Description
xrootd	/var/log/xrootd/server/xrootd.log	XRootD server daemon log
cmsd	/var/log/xrootd/server/cmsd.log	Cluster management log