en:praktikum:zugang

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision		 Previous revision
en:praktikum:zugang [2025/10/30 15:40] – [Alternative: Xpra] rhainichen:praktikum:zugang [2026/03/24 11:19] (current) – rhainich
Line 1: Line 1:
-====== Access to the laboratory computer ====== +====== Access to the Laboratory Computer ======
- +
-<WRAP center round info 60%> +
-From December 2024, to access the data reduction computer via SSH, you must first log in via VPN. The [[https://www.uni-potsdam.de/en/zim/angebote-loesungen/vpn | ZIM]] explains how to set up the VPN. Unfortunately the instructions are only available in German. If you have any questions about the VPN, please contact ZIM directly.  +
-</WRAP>+
  
 {{section>deng:praktikum:a12:status#Laboratory computer&noheader}} {{section>deng:praktikum:a12:status#Laboratory computer&noheader}}
-There are two ways to analyse the data collected during the placement: 1. you can carry out the analysis directly on the computer called //columba// at our university by prior arrangement or 2. you can log on to this computer from your home computer and then carry out the data analysis from home. + 
 +There are two ways to analyse the data collected during the lab course: 
 +1. Perform the analysis directly on the computer //columba// at the university (by prior arrangement). 
 +2. Log in to this computer remotely from another system (e.g. from home) and perform the analysis there. 
  
 ===== External Login ===== ===== External Login =====
-The data can also be analysed remotely, both from the physics institute's computer pool and from a home computer with an internet connection. There are several ways of accessing the data, each with its own advantages and disadvantages. Credentials can be obtained from the supervisors or will be announced by email after the introduction:  
  
-   User:      alpha  +Data analysis can also be carried out remotely, either from the computer pool of the Physics Institute or from a private computer with an internet connection. Several access methods are available, each with its own advantages and disadvantages. 
-   Password:  is given in the seminar   + 
 + 
 +==== Requirements ==== 
 + 
 +Credentials are provided by the supervisors or communicated during the introduction: 
 + 
 +   User:      alpha 
 +   Password:  will be provided 
 + 
 +**alpha** is used here as an example and must be replaced by the corresponding group name. 
 + 
 +<WRAP center round important 100%> 
 +To access the analysis computer from outside the university network, you must first connect to the university network via VPN. Instructions can be found on the [[https://www.uni-potsdam.de/de/zim/angebote-loesungen/vpn | ZIM website]]. 
 +</WRAP>
  
-**alpha** is given here as an example and must be replaced by the corresponding group name.  
  
 ==== Linux / Unix ==== ==== Linux / Unix ====
-Since the computers in the astrophysics are all operated with Linux, it's easy to log in from another computer with the same operating system. So you can do the complete evaluation from distance by logging in with a normal [[https://en.wikipedia.org/wiki/Secure_Shell | SSH]] connection on our laboratory computer. This also works for graphical output (i.e. view ''FITS'' files or text editors), but the performance crucially depends on the connection speed. In the computer pool at the university this is no problem but with a connection at home the speed may be low.  
  
-Login in the console with this command:+Since all astrophysics computers run Linux, logging in from another Linux/Unix system is straightforward. In most cases, a simple [[https://en.wikipedia.org/wiki/Secure_Shell | SSH]] login is sufficient to perform the complete data analysis remotely. 
 + 
 +Graphical output (e.g. FITS viewers or editors) is also supported, although performance depends on the connection speed. Within the university network this is usually not an issue, but from home the performance may be limited. 
 + 
 +Login via terminal: 
 + 
 +  ssh -Y alpha@columba.astro.physik.uni-potsdam.de
  
-<code>ssh -X alpha@columba.astro.physik.uni-potsdam.de</code>+You will be prompted for your password. The parameter **-Y** (capital Y) enables forwarding of graphical output.
  
-**alpha** is given here as an example and must be replaced by the corresponding group name. You will be asked for the password. The parameter **-X** (capital X) ensures that graphical output will be transferred so it can be displayed. 
  
 +=== Xpra ===
  
-=== Alternative: Xpra ===+Alternatively, you can use [[https://www.xpra.org/|Xpra]], which also uses //SSH// but allows more stable work with graphical applications, especially on slower connections.
  
-Alternatively you can log in with [[https://www.xpra.org/|Xpra]], which also communicates via //SSH//, but allows you to work with graphical output even with a poor internet connection. //Xpra// usually has to be installed from the package sources first. Once this is done, the following command establishes a connection to the laboratory computer+After installation, a connection can be established with:
  
    xpra seamless ssh:alpha@columba.astro.physik.uni-potsdam.de --start=konsole    xpra seamless ssh:alpha@columba.astro.physik.uni-potsdam.de --start=konsole
  
-The command is not very different from the one above, except that here the beginning and the end are slightly different. **alpha** has to be replaced by the group name here as well. If the connection has been established successfully, a //Xpra// icon or menu usually appears on the desktop (under Ubuntu it can be found in the upper right corner next to the network/volume/battery indicator). This menu can be used to configure //Xpra// as well as, via the menu item ''Start'', to start programs directly on the laboratory computer. //Xpra// has the nice advantage that the windows integrate seamlessly into the local system. +The command is similar to the SSH login above. Replace **alpha** with the appropriate group name.
  
-Furthermore it offers the possibility to disconnect from the //Xpra// session without ending it by typing ''xpra detach'' in a Terminal. This allows you to interrupt the session at any point and continue it later. All that is needed is the following console command:+After a successful connection, an //Xpra// icon or menu usually appears on the desktop (under Ubuntu in the upper-right corner near network/volume/battery indicators). From this menu, programs can be started directly on the remote system. The application windows integrate seamlessly into the local desktop. 
 + 
 +You can detach from a running session without terminating it: 
 + 
 +   xpra detach 
 + 
 +Reconnect with:
  
    xpra attach ssh:alpha@columba.astro.physik.uni-potsdam.de    xpra attach ssh:alpha@columba.astro.physik.uni-potsdam.de
  
-The //Xpra// session is terminated with:+Terminate the session with:
  
    xpra exit    xpra exit
Line 45: Line 67:
 ==== Windows ==== ==== Windows ====
  
-=== PuTTY and Xming === +Since Windows does not use the X-Window system, graphical output from Linux systems cannot be displayed directly. Therefore, an additional X server (X11 server) must be installed.
-Linux uses the X-Window-System to display graphical output while Windows has it's own system. That's the reason why graphical output from a Linux computer can not simply be displayed by Windows. To solve this you need to install an X-Window-Server designed to work with Windows. There are many options and programs that offer this functionality and we suggest these, slim freeware solutions:+
  
 +Recommended tools are:
  
-**Required programs** 
-  * [[http://www.chiark.greenend.org.uk/~sgtatham/putty/|PuTTY]] as the SSH-Client 
-  * [[http://www.straightrunning.com/XmingNotes/|Xming]] to display X-Window-Server windows 
  
-First install the server Xming, which optimally should be incorporated in the Windows autostart list. PuTTY is an executable that just requires a quick configuration:+=== MobaXterm ===
  
-  * click on the menu item //Session// and enter ''columba.astro.physik.uni-potsdam.de'' in the field //Hostname// +MobaXterm is an SSH client that includes a built-in X11 server.
-  * in //Connection// -> //SSH// -> //X11// check ''Enable X11 Forwarding'' to allow graphical output +
-  * in case of problems with the graphical output, enter ''localhost:0'' in the field //X display location// in //Connection// -> //SSH// -> //X11// +
  
- 
-=== MobaXterm === 
-MobaXterm is a SSH client which already includes the X11 Server. 
   * [[http://mobaxterm.mobatek.net/|MobaXterm]]   * [[http://mobaxterm.mobatek.net/|MobaXterm]]
  
-To increase the stability of the connection, it has proven useful to activate the "SSH keepalive" option and then restart MobaXterm.+To improve connection stability, it is recommended to enable the **SSH keepalive** option and restart the program.
  
-/* 
-**Configuration file for MobaXterm:** MobaXterm can use [[http://tucana.astro.physik.uni-potsdam.de/~mpietsch/Praktikumsrechner-a12.moba|this configuration file]] that has the required things already set. It just needs the password. To import the configuration file, start MobaXterm, right click in //Sessions// (left side) -> //Import sessions from file//, open the configuration file, and confirm with ''Yes''. 
-*/ 
  
-==== Operating system independent ==== +=== PuTTY and Xming ===
-=== X2G0 ===+
  
-In addition to the above mentioned possibilities, a //X2Go// server is also installed on the laboratory computer **columba**, which allows to work remotely and efficiently with graphical programs. The //X2Go// client is available for all major operating systems (Windows, Linux and MacOS).  +**Required software** 
 + 
 +  * [[http://www.chiark.greenend.org.uk/~sgtatham/putty/|PuTTY]] (SSH client) 
 +  * [[http://www.straightrunning.com/XmingNotes/|Xming]] (X server) 
 + 
 +Xming should be installed and ideally started automatically with the system. PuTTY requires only minimal configuration: 
 + 
 +  * Enter ''columba.astro.physik.uni-potsdam.de'' as hostname in the //Session// menu 
 +  * Enable ''X11 forwarding'' under //Connection → SSH → X11// 
 +  * In case of problems with the graphical output, set ''localhost:0'' as the display location 
 + 
 + 
 +==== Operating System Independent ==== 
 + 
 +=== X2Go === 
 + 
 +An //X2Go// server is installed on the laboratory computer **columba**, allowing efficient remote work with graphical applications. The X2Go client is available for all major operating systems, including Windows, Linux and macOS.
  
 {{ :ost:software:x2go_main_window.png?direct&400 |}} {{ :ost:software:x2go_main_window.png?direct&400 |}}
  
-After installing the client you can create a new session by clicking **Session** and then **New session ...**. In the window that opens you have to define the session parameters. +After installing the client, create a new session via //Session → New session ...//.
  
 <WRAP group> <WRAP group>
 <WRAP half column> <WRAP half column>
-{{ :ost:software:x2go_new_session.png |}}+{{ :ost:software:x2go_main_settings.png |}}
 </WRAP> </WRAP>
 <WRAP half column> <WRAP half column>
-{{ :ost:software:x2go_main_settings.png |}}+{{ :ost:software:x2go_input-output_settings.png |}}
 </WRAP> </WRAP>
 </WRAP> </WRAP>
  
-<WRAP group> +Configure the following parameters:
-<WRAP half column> +
-These include **session name**, **host**, **login**, and the **session type**. The **Session name** can be freely chosen and is only used to distinguish between different sessions. As **host** ''columba.astro.physik.uni-potsdam.de'' must be specified. As **Login** the respective user name like e.g. alpha has to be entered. +
  
-The next step is to go to the ''Input/Output'' tab. Here you can enable **Fullscreen** and disable **Set Display DPI** to connect in full screen without pixelation. However, this may affect the speed of the connection. +  * **Session name**: arbitrary 
 +  * **Host**: ''columba.astro.physik.uni-potsdam.de'' 
 +  * **Login**: e.g. ''alpha''
  
-After clicking on ''OK'' you can start the connection to **columba** by double clicking on the corresponding session entry in the main window of //X2Go//. Only the password for the respective account will be requested before the connection is established. The window that opens shows the MATE desktop, on which you can work as if you were sitting directly at the computer.+In the ''Input/Output'' tab:
  
-{{ :ost:software:x2go_4.png |}}+  * Enable **Fullscreen** 
 +  * Disable **Set display DPI**
  
-</WRAP> +After clicking ''OK'', start the session by double-clicking the entry. You will then be prompted to enter your password:
-<WRAP half column> +
-{{ :ost:software:x2go_input-output_settings.png |}} +
-</WRAP> +
-</WRAP>+
  
-<fc #ff0000>Attention Wayland users:</fc> Under Wayland, it is possible that the current client does not work properly and simply crashes when logging in, in this case it may help to start the client from the command line with+{{ :ost:software:x2go_4.png |}} 
 + 
 +<fc #ff0000>Attention Wayland users:</fc> 
 +If the client crashes, try starting it via:
  
     env QT_QPA_PLATFORM=xcb x2goclient     env QT_QPA_PLATFORM=xcb x2goclient
  
-=== Logging in via Remote Desktop Protocol ===+ 
 +=== Remote Desktop Protocol ===
  
 <WRAP center round important 60%> <WRAP center round important 60%>
-This method is in beta stage+This method is currently in beta.
 </WRAP> </WRAP>
  
 <WRAP center round alert 60%> <WRAP center round alert 60%>
-Unfortunately, this method is not working at the moment.+This method is currently not working reliably.
 </WRAP> </WRAP>
  
-In addition to the methods described above, you can also log in to columba using the RDP protocol. The protocol developed by Microsoft is very performant and offers the possibility of displaying the entire desktop without any major loss of speed.  There is a free implementation for Linux, so we can also use this with columba. However, since RDP is not considered the most secure method, you must first establish an SSH tunnel to columba before you can connect to the RDP server.  +In addition to the above methods, you can log in to columba using the Remote Desktop Protocol (RDP). This protocol, developed by Microsoft, is highly efficient and enables the entire desktop to be displayed without any significant loss of speed.  There is a free Linux implementation, so we can use this with columba too. However, as RDP is not considered the most secure method, you must first establish an SSH tunnel to Columba before connecting to the RDP server.
- +
-Under Linux, [[https://remmina.org/ | Remmina]] can be used for this, which can be installed in the vast majority of distributions via the package sources if it is not already supplied with the distribution.   +
  
 <WRAP group> <WRAP group>
 <WRAP half column> <WRAP half column>
 +** Linux **
  
-== Configuration instructions Linux: ==+On Linux, [[https://remmina.org/ | Remmina]] is the recommended option:
  
-  * After Remmina has been started, click on the plus symbol in the top left corner. +  * Start the program and create a new connection 
-  * This opens the configuration dialog +  * Enter a name for the configuration 
-  * Enter the following or activate the corresponding option: +  * Server: ''127.0.0.1:3389'' 
-    - Name for the configuration +  * Enter username and password 
-    - Server address: 127.0.0.1:3389 +  * Enable ''Use client resolution'' 
-    - User name + 
-    - Password +Under ''SSH Tunnel'': 
-    - ''Use client resolution'' + 
-  * Then click on ''SSH Tunnel'' and add the following configuration or enable the corresponding option: +  * Enable ''SSH tunnel'' 
-    - ''Enable SSH tunnel''. +  * Server: ''columba.astro.physik.uni-potsdam.de'' 
-    - ''Custom'' +  * Enter username and password 
-    - Server address: columba.astro.physik.uni-potsdam.de + 
-    - Username +Start the connection via ''Save and Connect''. 
-    - Password + 
-  * Then finish the configuration by clicking on ''Save and Connect''. +If you are satisfied with the connection speed, the ''Advanced'' tab allows you to improve the quality of your connection.
-  * Remmina will then connect to columba +
-  * If you are satisfied with the connection speed, you can increase the quality of the connection in the ''Advanced'' tab. +
-  * After saving the configuration, you will find it under the name you entered in the list that Remmina displays when the program starts. Doubleclick on the entry to easily connect to the columba.+
  
 </WRAP> </WRAP>
Line 172: Line 195:
 <WRAP group> <WRAP group>
 <WRAP half column> <WRAP half column>
-**Configuration Instructions for Windows 11:**  +** Windows 11 ** 
-  * On Windows, you must first set up the SSH tunnel before you can use the Windows RDP client because it does not provide this functionality itself. + 
-  * To do this, you must first open a PowerShell window. +Firstly, an SSH tunnel must be created using PowerShell, as the Windows RDP client does not support this: 
-  * In this window, type the command ''ssh -L 3399:127.0.0.1:3389 alpha@columba.astro.physik.uni-potsdam.de''. Replace ''alpha'' with the appropriate group name.  + 
-  +   ssh -L 3399:127.0.0.1:3389 alpha@columba.astro.physik.uni-potsdam.de 
-[{{ost:software:power_shell_ssh-tunnel.jpg| PowerShell with SSH tunnel command }}]+ 
 +You can then connect using an RDP client. The following settings must be configured: 
 + 
 +   * Computer: ''localhost:3399'' 
 +   * User name: e.g. ''alpha'' 
 +   * ''Allow me to save credentials'' (optional, it may be necessary to click on ''Show Options'' first) 
 +    
 +Click ''Connect'' to establish the connection. You will then be prompted to enter your password. 
  
-  * You can then start the RDP client and enter the following configuration or enable the appropriate option: 
-    - Computer: ''localhost:3399'' 
-    - User name 
-    - ''Allow me to save credentials'' (optional) 
-  * It may be necessary to click on ''Show Options'' first. 
-  * Click on ''Connect'' to establish the connection. The password prompt will follow. 
 </WRAP> </WRAP>
 <WRAP half column> <WRAP half column>
Line 191: Line 215:
 </WRAP> </WRAP>
  
-===== External Login from the computer pool in the Physics Institute ===== 
-Also the Linux computers in the computer pool of the Physics Institute (room 2.28.1.101) can be used to login on the lab computer. See the description here: [[en:praktikum:zugang#linux_unix|Linux]]. The computers share the fast internet access of the University and so the transfer rate, i.e. for graphical output it is sufficient to work. To get an account for the computer pool, ask Mr H. Todt (room 2.28.2.004). 
  
 +===== External Login from the Physics Computer Pool =====
  
-===== Working directly on the data reduction computer ===== +The computers in the Physics computer pool (room 2.28.1.101) can also be used to access the laboratory computer via SSH. Due to the high network speed, efficient work is possible without prior reservation.
-The computer for the laboratory courses shall be used for data reduction. It is in room 2.009 in the Institute in Golm and can be booked, i.e. request a timeslot by email. +
  
-These timeslots are already booked: {{page>deng:praktikum:a12:reservation}}+Accounts can be requested from Mr H. Todt (room 2.28.2.004).
  
  
-===== Linux Sheet Paper ===== +===== Working Directly on the Data Reduction Computer =====
-This [[http://www.cheat-sheets.org/saved-copy/fwunixref.pdf|pdf file]] list the absolutely basic commands for a Linux console. The [[http://cli.learncodethehardway.org/bash_cheat_sheet.pdf|Bash Cheat Sheet]] contains some further commands.+
  
 +The laboratory computer (columba) is available for on-site data analysis (room 2.28.2.009) and can be booked via email.
  
-===== Access to files by SFTP ===== 
  
-Pure file transfer is possible, independent of the computer system, by logging in with SFTP (Secure File Transfer Protocol). All you need is a program that can run SFTP transfers, be it console based or graphical (i.e. [[http://winscp.net/eng|WinSCP]]).+===== File Transfer via SFTP =====
  
-The login information are in principle the same as for the SSH client:+Regardless of the operating system, it is possible to log in via SFTP (SSH File Transfer Protocol) solely for the purpose of exchanging data. This requires an SFTP programme. These are available for virtually every operating system, whether console-based or with a graphical user interface. Users accustomed to a graphical user interface can use [[http://winscp.net/eng|WinSCP]], for example, as a free SFTP client. 
 + 
 +The login details for the SFTP client are identical to those for SSH access:
  
    Server:   columba.astro.physik.uni-potsdam.de    Server:   columba.astro.physik.uni-potsdam.de
    Protocol: SFTP    Protocol: SFTP
    User:     alpha    User:     alpha
-   Password: as before+   Password: as provided 
 + 
 +Similarly, **alpha** is used here merely as an example and must be replaced with the relevant group name.  
 + 
 +**Note:** SFTP is intended for file transfer only. It does not allow execution of programs. 
  
-**alpha** is given here as an example and must be replaced by the corresponding group name. +===== Linux Cheat Sheets =====
  
-**Attention:** In contrast to the login methods described in the previous sections, SFTP is just for file transfer. It will not let you work on data reduction or alike.+   * [[http://www.cheat-sheets.org/saved-copy/fwunixref.pdf|Basic commands]]
  
  
-/* +[[en:praktikum:index|Laboratory Courses – Overview]]
-====== Virtual laboratory computer ====== +
-We offer a virtual laboratory computer, see [[en:software:howto_virtualbox_ubuntu|here]]. +
-*/+
  
-[[en:praktikum:index|Laboratory Courses- overview]] 
  • en/praktikum/zugang.1761838829.txt.gz
  • Last modified: 2025/10/30 15:40
  • by rhainich