Connecting Thinstation Linux 5.1 Diskless Clients to a Citrix XenApp Farm
This material was compiled to describe the sequence of actions for turning obsolete computer equipment into full-fledged terminal diskless clients loaded over the network. There is enough such information on the Internet now, and although it is aimed at solving the same problem, still, basically, there is a description of Remote Desktop (RDP) connections, less often VMWare View. Here, as you can guess from the name, everything that is needed to connect a Thinstation Linux based diskless client to the Citrix XenApp 6 server farm will be described. This article is not a step-by-step instruction and is not intended for beginners.
To download images over the network, DHCP and TFTP servers are required. The boot server can be deployed on Linux and on Windows, practically I used the configuration on Linux, so the emphasis here will be on this option, nevertheless, it can all be successfully configured on Windows as well. The process of installing and configuring a DHCP and TFTP server is trivial, but we will need to specify additional parameters.
For dhcpd, the following lines are required in dhcpd.conf:
For DHCP under Windows Server, you need to add options 067 and 066 with the values that were given above for dhcpd. As for the TFTP server, under Windows there is tftpd32, it can work as a service, and has all the necessary functions. Under Linux, xinetd, which is available in many distributions, is perfect.
Configuration file /etc/xinetd.d/tftp:
Installing and configuring a Citrix XenApp server farm is beyond the scope of this article; it is understood that the farm already exists and is running. For Thinstation Linux citrix clients to successfully connect to the farm, the following configuration changes are required:
In addition to configuration changes, it is not superfluous to take into account the following:
Download the latest release of Thinstation Linux, and prepare for assembly. The commands are executed from root, it is understood that the environment for building Thinstation Linux is loaded and will work in / thinstation:
Next, we edit the configuration files build.conf and thinstation.conf.buildtime according to our requirements. In the future, you can fine-tune everything, make different configurations for different hardware, remove everything superfluous to minimize the image size, etc., but for a start it is better to do everything as simple as possible to avoid errors due to additional complications. Therefore, I will only mention important parameters that need to be uncommented in build.conf, modules can be ignored, because this is our first test assembly without optimizations, so we will build an image with all the modules:
Packages:
Parameters:
thinstation.conf.buildtime, which comes by default in the Thinstation Linux distribution, is better to copy to a separate file, and create a new one with the following contents:
Download the linuxx86_12.1.0.203066.tar.gz file from here:
www.citrix.com/downloads/citrix-receiver/linux/receiver-for-linux-121.html
and put it in / thinstation / downloads. The build script of Thinstation Linux can also download what you need during the build process, I'm just used to using my distributions.
We start image assembly:
At the end of the build process, go to the directory / thinstation / build / packages / ica / opt / Citrix / ICAClient / config and fix the file appsrv.ini.tpl. By default, the citrix client installed in Thinstation Linux can only connect to the specified XenApp server, which does not meet our requirements. We need to connect to the application published on the XenApp server farm, this ensures greater reliability and fault tolerance of the solution. The client is not tied to a specific server, and when connected, the broker switches the client to the least loaded server of the farm. It goes without saying that in this case the servers should be identical in configuration and users should have roaming profiles configured correctly, but this is a separate issue.
Let's bring appsrv.ini.tpl to the following form:
Again we start image assembly:
After the assembly is completed, the files we need will appear in the / thinstation / build / boot-images / pxe directory. Copy the contents of / thinstation / build / boot-images / pxe to / tftpboot.
Create thinstation.conf.group-1280@60, thinstation.conf.group-desktop, thinstation.conf.group-mouse, thinstation.hosts:
thinstation.conf.group-1280@60 in / tftpboot
thinstation.conf.group-mouse
thinstation.conf.group-desktop
thinstation.hosts
System requirements: network card with support for downloading via the PXE LAN BOOTROM network and 512Mb RAM. If you fine-tune the image for iron, exclude everything superfluous, and if the computer has a motherboard with integrated video, then configure the RAM reservation in the BIOS for video memory less (2-8MB), then you can shrink 256Mb as well, but I would recommend having would be 320Mb.
Of the settings, the main thing that is required is to enable network boot in the BIOS, and the BIOS should have the correct time, otherwise there may be problems with the SSL connection (certificate validity period errors).
The goal was to make the diskless client work as close as possible to the local computer, so there are no additional shells, the citrix client starts immediately, and connects to the XenApp farm according to the configuration. At the end of the download, the user immediately sees the Windows login screen:
Thank you for attention.
Image and configuration download server
To download images over the network, DHCP and TFTP servers are required. The boot server can be deployed on Linux and on Windows, practically I used the configuration on Linux, so the emphasis here will be on this option, nevertheless, it can all be successfully configured on Windows as well. The process of installing and configuring a DHCP and TFTP server is trivial, but we will need to specify additional parameters.
For dhcpd, the following lines are required in dhcpd.conf:
filename "pxelinux.0";
next-server X.X.X.X;
For DHCP under Windows Server, you need to add options 067 and 066 with the values that were given above for dhcpd. As for the TFTP server, under Windows there is tftpd32, it can work as a service, and has all the necessary functions. Under Linux, xinetd, which is available in many distributions, is perfect.
Configuration file /etc/xinetd.d/tftp:
# default: off
# description: The tftp server serves files using the trivial file transfer \
# protocol. The tftp protocol is often used to boot diskless \
# workstations, download configuration files to network-aware printers, \
# and to start the installation process for some operating systems.
service tftp
{
socket_type = dgram
protocol = udp
wait = yes
user = root
server = /usr/sbin/in.tftpd
server_args = -s /tftpboot
disable = no
per_source = 11
cps = 100 2
flags = IPv4
}
Preparing Citrix XenApp to Connect Citrix Clients to Linux
Installing and configuring a Citrix XenApp server farm is beyond the scope of this article; it is understood that the farm already exists and is running. For Thinstation Linux citrix clients to successfully connect to the farm, the following configuration changes are required:
- Publish the desktop as an application (let's call it Desktop) and add to it all the farm servers on which you plan to start users.
- Set the Desktop Launches user policy to Allowed state. You can enable the Desktop Launches policy not globally for the entire farm, but only on the farm servers on which our Desktop application is published. To do this, on each such server you need to open the local group policy editor (gpedit.msc) and then in the user configuration, enable the Desktop Launches policy in Citrix Policies.
In addition to configuration changes, it is not superfluous to take into account the following:
- Citrix Web Interface, Citrix Secure Gateway (as well as Access Gateway, Netscaler, etc.) are not involved in the connection of our diskless clients. The brokers for the connection are the servers specified in the Thinstation Linux configuration (thinstation.conf.group-desktop). You can make all servers brokers, or you can assign this role to separate, less loaded servers.
- The Linux Citrix client does not support Session Reliability and connects via standard XML (TCP / 80 or TCP / 8080 depending on the configuration) + ICA TCP / 1494, or via SSL Relay (TCP / 443 by default).
- The Linux Citrix client does not support connection priorities for worker groups, i.e. no specially configured Load Balancing Policies will work.
Build and configure a Thinstation Linux boot image
Download the latest release of Thinstation Linux, and prepare for assembly. The commands are executed from root, it is understood that the environment for building Thinstation Linux is loaded and will work in / thinstation:
cd /
git clone --depth 1 git://thinstation.git.sourceforge.net/gitroot/thinstation/thinstation
cd thinstation
./setup-chroot
q
exit
cd /thinstation/build
Next, we edit the configuration files build.conf and thinstation.conf.buildtime according to our requirements. In the future, you can fine-tune everything, make different configurations for different hardware, remove everything superfluous to minimize the image size, etc., but for a start it is better to do everything as simple as possible to avoid errors due to additional complications. Therefore, I will only mention important parameters that need to be uncommented in build.conf, modules can be ignored, because this is our first test assembly without optimizations, so we will build an image with all the modules:
Packages:
package xorg7-vesa
package ica
package sshd
Parameters:
param rootpasswd <пароль рута>
param basepath .
param icaencryption true
thinstation.conf.buildtime, which comes by default in the Thinstation Linux distribution, is better to copy to a separate file, and create a new one with the following contents:
KEYBOARD_MAP=en
MOUSE_ACCELERATION=1
MOUSE_RESOLUTION=100
MOUSE_SENSITIVITY=1
X_MOUSE_PROTOCOL="IMPS/2"
X_MOUSE_DEVICE=/dev/input/mice
POWERBTN_ACTION=Off
CUSTOM_CONFIG=Off
DAILY_REBOOT=On
SCREEN_BLANK_TIME=0
SCREEN_STANDBY_TIME=0
SCREEN_SUSPEND_TIME=0
SCREEN_OFF_TIME=0
DONT_VT_SWITCH_STATE=TRUE
DONT_ZAP_STATE=TRUE
NET_USE_DHCP=On
NET_HOSTNAME=ts_*
NET_FILE_ENABLED=On
NET_TELNETD_ENABLED=Off
RECONNECT_PROMPT=MENU
TIME_ZONE=Europe/Moscow
NET_TIME_SERVER=<ваш NTP сервер, FQDN-имя или IP-адрес>
NET_REMOTE_ACCESS_FROM="0.0.0.0"
XKEYBOARD="us,ru"
XKBVARIANT=",winkeys"
TFTP_BLOCKSIZE=1024
Download the linuxx86_12.1.0.203066.tar.gz file from here:
www.citrix.com/downloads/citrix-receiver/linux/receiver-for-linux-121.html
and put it in / thinstation / downloads. The build script of Thinstation Linux can also download what you need during the build process, I'm just used to using my distributions.
We start image assembly:
cd /thinstation
./setup-chroot
q
cd build
./build --allmodules
At the end of the build process, go to the directory / thinstation / build / packages / ica / opt / Citrix / ICAClient / config and fix the file appsrv.ini.tpl. By default, the citrix client installed in Thinstation Linux can only connect to the specified XenApp server, which does not meet our requirements. We need to connect to the application published on the XenApp server farm, this ensures greater reliability and fault tolerance of the solution. The client is not tied to a specific server, and when connected, the broker switches the client to the least loaded server of the farm. It goes without saying that in this case the servers should be identical in configuration and users should have roaming profiles configured correctly, but this is a separate issue.
Let's bring appsrv.ini.tpl to the following form:
Description=$ICAX_TITLE
WinStationDriver=ICA 3.0
TransportDriver=TCP/IP
DoNotUseDefaultCSL=Off
EncryptionLevelSession=$ICAX_ENCRYPTION
Compress=$ICAX_COMPRESS
AudioBandwidthLimit=$ICAX_AUDIO_QUALITY
ClientAudio=$ICAX_AUDIO
UseDefaultSettingForColormap=Yes
ZLMouseMode=2
ZLKeyboardMode=2
NoWindowManager=True
UseFullScreen=Yes
Address=$ICAX_TITLE
TWIMode=$ICAX_SEAMLESS_WINDOW
DisableCtrlAltDel=$ICAX_DISABLECTRLALTDEL
Again we start image assembly:
cd /thinstation
./setup-chroot
q
cd build
./build --allmodules
After the assembly is completed, the files we need will appear in the / thinstation / build / boot-images / pxe directory. Copy the contents of / thinstation / build / boot-images / pxe to / tftpboot.
Create thinstation.conf.group-1280@60, thinstation.conf.group-desktop, thinstation.conf.group-mouse, thinstation.hosts:
thinstation.conf.group-1280@60 in / tftpboot
SCREEN_RESOLUTION="1280x1024"
SCREEN_HORIZSYNC="30-65"
SCREEN_VERTREFRESH="60"
thinstation.conf.group-mouse
MOUSE_RESOLUTION=100
MOUSE_ACCELERATION=1
thinstation.conf.group-desktop
SESSION_0_TITLE="Desktop"
SESSION_0_TYPE=ica
SESSION_0_AUTOSTART=On
SESSION_0_ICA_SERVER=Desktop
SESSION_0_ICA_ENCRYPTION="Basic"
SESSION_0_ICA_COMPRESS=Off
SESSION_0_ICA_AUDIO_QUALITY=High
SESSION_0_ICA_AUDIO=On
SESSION_0_ICA_SEAMLESS_WINDOW=Off
SESSION_0_ICA_SMARTCARD=Off
SESSION_0_ICA_DISABLECTRLALTDEL=On
ICA_BROWSER_PROTOCOL=HTTPonTCP
ICA_WFCLIENT_HttpBrowserAddress=:8080
ICA_WFCLIENT_HttpBrowserAddress2=:8080
ICA_WFCLIENT_HttpBrowserAddress3=:8080
ICA_WFCLIENT_InitialProgram=#Desktop
thinstation.hosts
# Hostname MAC Resolution Mouse_settings Session
thinstation1 001122334455 1280@60 mouse desktop
Diskless client preparation
System requirements: network card with support for downloading via the PXE LAN BOOTROM network and 512Mb RAM. If you fine-tune the image for iron, exclude everything superfluous, and if the computer has a motherboard with integrated video, then configure the RAM reservation in the BIOS for video memory less (2-8MB), then you can shrink 256Mb as well, but I would recommend having would be 320Mb.
Of the settings, the main thing that is required is to enable network boot in the BIOS, and the BIOS should have the correct time, otherwise there may be problems with the SSL connection (certificate validity period errors).
What is the result and how does it look
The goal was to make the diskless client work as close as possible to the local computer, so there are no additional shells, the citrix client starts immediately, and connects to the XenApp farm according to the configuration. At the end of the download, the user immediately sees the Windows login screen:
Thank you for attention.