Install XRootD Standalone

EL7 version compatibility

There is an incompatibility with EL7 < 7.5 due to an issue with the globus-gsi-proxy-core package

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.

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 the XRootD Standalone server, run the following Yum command:

[email protected] # yum install osg-xrootd-standalone

Configuring XRootD

To configure XRootD as a standalone server, you will modify /etc/xrootd/xrootd-standalone.cfg and the config files under /etc/xrootd/config.d/ as follows:

1. Configure a rootdir in /etc/xrootd/config.d/10-common-site-local.cfg, to point to the top of the directory hierarchy which you wish to serve via XRootD.

   set rootdir = <DIRECTORY>
   

   Warning

   Do not set rootdir to /. This might result in serving private information.

2. If you want to limit the sub-directories to serve under your configured rootdir, comment out the all.export / directive in /etc/xrootd/config.d/90-osg-standalone-paths.cfg, and add an all.export directive for each directory under rootdir that you wish to serve via XRootD.

   This is useful if you have a mixture of files under your rootdir, for example from multiple users, but only want to expose a subset of them to the world.

   For example, to serve the contents of /data/store and /data/public (with rootdir configured to /data):

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

   If you want to serve everything under your configured rootdir, you don't have to change anything.

   Note

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

3. In /etc/xrootd/config.d/10-common-site-local.cfg, add a line to set the resourcename variable to the resource name of your XRootD service. For example, the XRootD service registered at the University of Florida site should set the following configuration:

   set resourcename = UFlorida-XRD
   

   Note

   CMS sites should follow CMS policy for resourcename

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 Hadoop support (EL 7 Only)

Hadoop File System (HDFS) based sites should utilize the xrootd-hdfs plugin to allow XRootD to access their storage:

1. Install the XRootD HDFS plugin package:

   [email protected] # yum install xrootd-hdfs
   

2. Add the following configuration to /etc/xrootd/xrootd-clustered.cfg:

   ofs.osslib /usr/lib64/libXrdHdfs.so
   

For more information, see the HDFS installation documents.

Enabling multi-user support

By default XRootD servers write files on the storage system aa the Unix user xrootd instead of the authenticated user. The xrootd-multiuser plugins changes this behaviour:

1. Install the XRootD multi-user plugin:

   [email protected] # yum install xrootd-multiuser
   

2. Start the XRootD process in privileged mode:

   [email protected] # systemctl [email protected]
   

Bug

The multiuser support is incompatible with checksums.

Note

This is not necessary when XRootD is used for read-only access

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. If you are not setting up a CMS site, you can skip this section.

yum install --enablerepo=osg-contrib xrootd-cmstfc

You will need to add your storage.xml to /etc/xrootd/storage.xml and then add the following line to your XRootD configuration:

# Integrate with CMS TFC, placed in /etc/xrootd/storage.xml
oss.namelib /usr/lib64/libXrdCmsTfc.so file:/etc/xrootd/storage.xml?protocol=hadoop

Add the orange text only if you are running hadoop (see below).

See the CMS TWiki for more information:

• https://twiki.cern.ch/twiki/bin/view/Main/XrootdTfcChanges
• https://twiki.cern.ch/twiki/bin/view/Main/HdfsXrootdInstall

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]
XRootD Multiuser	[email protected]	See XRootD multiuser for more info

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 …	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:

Note

If you have configured authentication/authorization for XRootD, be sure you have given yourself the necessary permissions to run these tests. For example, if you are using a grid proxy, make sure your DN is mapped to a user in /etc/grid-security/grid-mapfile, and make sure you have a valid proxy on your local machine. Also, ensure that the Authfile on the XRootD server gives write access to the Unix user you will get mapped to.

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. 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
      

Registering an XRootD Standalone Server

To register your XRootD server, follow the general registration instructions here with the following XRootD-specific details:

1. Add an XRootD component: section to the Services: list, with any relevant fields for that service. This is a partial example:

   ...
   FQDN: <FULLY QUALIFIED DOMAIN NAME>
   Services:
     XRootD component:
       Description: Standalone XRootD server
   ...
   

   Replacing <FULLY QUALIFIED DOMAIN NAME> with your XRootD server's DNS entry.

2. If you are setting up a new resource, set Active: false. Only set Active: true for a resource when it is accepting requests and ready for production.

Getting Help

To get assistance. please use the Help Procedure page.

Reference

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

Service Configuration

The configuration that your XRootD service uses is determined by the service name given to systemctl. To use the standalone config, you would start XRootD with the following command:

[email protected] # systemctl start [email protected]

File locations

Service/Process	Configuration File	Description
xrootd	/etc/xrootd/xrootd-standalone.cfg	Main XRootD configuration
	/etc/xrootd/config.d/	Drop-in configuration dir
	/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