Installing and Maintaining a GridFTP Server

About This Guide

This page explains how to install the stand-alone Globus GridFTP server, which is an extension of the File Transfer Protocol (FTP) for grid computing. The aim of GridFTP is to provide a more reliable and high performance file transfer.

The osg-gridftp package contains components necessary to set up a stand-alone GridFTP server and tools used to monitor and report its performance. A stand-alone GridFTP server might be used under the following circumstances:

• You are serving VOs that use storage heavily (CMS, ATLAS, CDF, and D0) and your site has more than 250 cores
• Your site will be managing more than 50 TB of disk space
• You want a simple front-end to a filesystem allowing access over WAN - for example NFS.

Note

This document is for a standalone GridFTP server on top of POSIX storage. We have two specialized documents for Hadoop Distributed File System (HDFS) and XRootD based storage:

• Install and configure a GridFTP server on top of HDFS.
• Install and configure a GridFTP server on top of XRootD.

Before Starting

Before starting the installation process you will need to fulfill these prerequisites.

• Ensure the host has a supported operating system
• Obtain root access to the host
• Prepare the required Yum repositories
• Install CA certificates
• SSL Certificate: The GridFTP service uses a host certificate at /etc/grid-security/hostcert.pem and an accompanying key at /etc/grid-security/hostkey.pem
• Network ports: GridFTP listens on TCP port 2811 and the list of ports configured by the GLOBUS_TCP_SOURCE_RANGE environment variable.

Installing GridFTP

First, you will need to install the GridFTP meta-package:

[email protected] # yum install osg-gridftp

Configuring GridFTP

Configuring authentication

To configure which virtual organizations and users are allowed to use your GridFTP server, follow the instructions in the LCMAPS VOMS plugin document.

Set port ranges

As mentioned above, GridFTP uses port 2811 for control communication as well as a range of ports for the data transfer. This range of ports has to defined by setting the variable GLOBUS_TCP_PORT_RANGE within the configuration file: /etc/sysconfig/globus-gridftp-server as it is shown in the next example. This range has to be open within your firewall for inbound communication.

$GLOBUS_TCP_PORT_RANGE 50000,51000

Optional configuration

Setting transfer limits for GridFTP-HDFS

To set a limit on the total or per-user number of transfers, create /etc/sysconfig/gridftp-hdfs and set the following configuration:

export GRIDFTP_TRANSFER_LIMIT="80"
export GRIDFTP_DEFAULT_USER_TRANSFER_LIMIT="50"
export GRIDFTP_<UNIX USERNAME>_USER_TRANSFER_LIMIT="40"

In the above configuration:

• There would be no more than 80 transfers going at a time, across all users.
• By default, any single user can have no more than 50 transfers at a time.
• The <UNIX USERNAME> user has a more stringent limit of 40 transfers at a time.

Note

This limits are per gridftp server. If you have several gridftp servers you may want to have this limits divided by the number of gridftp servers at your site.

Modifying the environment

Environment variables are stored in /etc/sysconfig/globus-gridftp-server which is sourced on service startup. If you want to change LCMAPS log levels, or GridFTP port ranges, you can edit them there.

#Uncomment and modify for firewalls
#export GLOBUS_TCP_PORT_RANGE=min,max
#export GLOBUS_TCP_SOURCE_RANGE=min,max

Note that the variables GLOBUS_TCP_PORT_RANGE and GLOBUS_TCP_SOURCE_RANGE can be set here to allow GridFTP to navigate around firewall rules (these affect the inbound and outbound ports, respectively).

To troubleshoot LCMAPS authorization, you can add the following to /etc/sysconfig/globus-gridftp-server and choose a higher debug level:

# level 0: no messages, 1: errors, 2: also warnings, 3: also notices,
#  4: also info, 5: maximum debug
LCMAPS_DEBUG_LEVEL=2

Output goes to /var/log/messages by default. Do not set logging to 5 on any production systems as that may cause systems to slow down significantly or become unresponsive.

Configuring a multi-homed server

The GridFTP uses control connections, data connections and IPC connections. By default it listens in all interfaces but this can be changed by editing the configuration file /etc/gridftp.conf.

To use a single interface you can set hostname to the Hostname or IP address to use:

hostname IP-TO-USE

You can also set separately the control_interface, data_interface and ipc_interface. On systems that have multiple network interfaces, you may want to associate data transfers with the fastest possible NIC available. This can be done in the GridFTP server by setting data_interface:

control_interface IP-TO-USE
data_interface IP-TO-USE
ipc_interface IP-TO-USE

For more options available for the GridFTP server, read the comments in the configuration file (/etc/gridftp.conf) or see the GridFTP manual.

Monitoring

Enabling GridFTP transfer probe

The OSG monitoring of GridFTP is carried out by the GridFTP Gratia Probe which is installed by the package: gratia-probe-gridftp-transfer Assuming you installed GridFTP using the osg-gridftp or osg-se-hadoop-gridftp RPM, this package will already be installed.

Here are the most relevant file and directory locations:

Purpose	Needs Editing?	Location
Probe Configuration	Yes	/etc/gratia/gridftp-transfer/ProbeConfig
Probe Executables	No	/usr/share/gratia/gridftp-transfer
Log files	No	/var/log/gratia
Temporary files	No	/var/lib/gratia/tmp

The RPM installs the Gratia probe into the system crontab, but does not configure it. The configuration of the probe is controlled by the file

/etc/gratia/gridftp-transfer/ProbeConfig

This is usually one XML node spread over multiple lines. Note that comments (#) have no effect on this file. You will need to edit the following:

Attribute	Needs Editing	Value
ProbeName	Maybe	This should be set to "gridftp-transfer:<HOSTNAME>", where <HOSTNAME> is the fully-qualified domain name of your gridftp host.
CollectorHost	Maybe	Set to the hostname and port of the central collector. By default it sends to the OSG collector. See below.
SiteName	Yes	Set to the resource group name of your site as registered in OIM.
GridftpLogDir	Yes	Set to /var/log, or wherever your current gridftp logs are located
Grid	Maybe	Set to "ITB" if this is a test resource; otherwise, leave as OSG.
UserVOMapFile	No	This should be set to /var/lib/osg/user-vo-map; see below for information about this file.
SuppressUnknownVORecords	Maybe	Set to 1 to suppress any records that can't be matched to a VO; 0 is strongly recommended.
SuppressNoDNRecords	Maybe	Set to 1 to suppress records that can't be matched to a DN; 0 is strongly recommended.
EnableProbe	Yes	Set to 1 to enable the probe.

Selecting a collector host

The collector is the central server which logs the GridFTP transfers into a database. There are usually two options:

1. OSG Transfer Collector: This is the primary collector for transfers in the OSG. Use CollectorHost="gratia-osg-prod.opensciencegrid.org:80".
2. OSG-ITB Transfer Collector: This is the test collector for transfers in the OSG. Use CollectorHost=" gratia-osg-itb.opensciencegrid.org:80".

Managing GridFTP

In addition to the GridFTP 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
Gratia	gratia-probes-cron	Accounting software
GridFTP	globus-gridftp-server

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 on boot	systemctl enable <SERVICE-NAME>
Disable a service from starting on boot	systemctl disable <SERVICE-NAME>

Validation

GridFTP

1. Acquire a user certificate

2. Find your subject DN:

   [email protected] # openssl x509 -in <CERITIFICATE_FILE.pem> -noout -subject
   

3. Map your DN to a non-root user.

4. As the non-root user, generate your proxy

   [email protected] # voms-proxy-init
   

5. Create a test file to be transfered

   [email protected] # echo "Hello World!" > /tmp/hello_world
   

6. Transfer the file we just created

   [email protected] # globus-url-copy file:///tmp/hello_world gsiftp://yourhost.yourdomain/tmp/hello_world
   

7. To verify that the authentication is working, we could remove our proxy and execute the last command again, this time it should fail.

   [email protected] # voms-proxy-destroy
   [email protected] # globus-url-copy file:///tmp/hello_world gsiftp://yourhost.yourdomain/tmp/hello_world
   

Warning

Keep in mind that when invoked as root, globus-url-copy will attempt to use the host certificate instead of your user certificate, which could produce confusing results.

Note

If the binary globus-url-copy is not available on your system, you can get it by installing globus-gass-copy-progs:

[email protected] # yum install globus-gass-copy-progs

Gratia Probe

1. Run the Gratia probe once by hand to check for functionality:

   [email protected] # /usr/share/gratia/gridftp-transfer/gridftp-transfer_meter
   

2. Look in the log files in /var/log/gratia/<date>.log and make sure there are no error messages printed. Look for any abnormal termination and report it if it is a non-trivial site issue.

Getting Help

For assistance, please use this page.

Reference

• GridFTP administration manual
• GridFTP tutorial

Configuration and Log Files

Service/Process	Configuration File	Description
GridFTP	/etc/sysconfig/globus-gridftp-server	Environment variables for GridFTP and LCMAPS
	/usr/share/osg/sysconfig/globus-gridftp-server-plugin	Where environment variables for GridFTP plugin are included
Gratia Probe	/etc/gratia/gridftp-transfer/ProbeConfig	GridFTP Gratia Probe configuration
Gratia Probe	/etc/cron.d/gratia-probe-gridftp-transfer.cron	Cron tab file

Service/Process	Log File	Description
GridFTP	/var/log/gridftp.log	GridFTP transfer log
	/var/log/gridftp-auth.log	GridFTP authorization log
Gratia probe	/var/logs/gratia

Certificates

Certificate	User that owns certificate	Path to certificate
Host certificate	root	/etc/grid-security/hostcert.pem and /etc/grid-security/hostkey.pem

Instructions to request a service certificate.

Make sure you have installed the CA certificates

Users

For this package to function correctly, you will have to create the users needed for grid operation. Any Unix username that can be mapped by LCMAPS VOMS should be created on the GridFTP host.

For example, VOs newly-added to the LCMAPS VOMS configuration will not be able to transfer files until the corresponding Unix user account is created.

Networking

Service Name	Protocol	Port Number	Inbound	Outbound	Comment
GridFTP data channels	tcp	GLOBUS_TCP_PORT_RANGE	X		contiguous range of ports is necessary.
GridFTP data channels	tcp	GLOBUS_TCP_SOURCE_RANGE		X	contiguous range of ports is necessary.
GridFTP control channel	tcp	2811	X