Difference between revisions of "SPO600 Servers"

From CDOT Wiki
Jump to: navigation, search
(Available Servers)
(Common SSH Problems)
(21 intermediate revisions by the same user not shown)
Line 1: Line 1:
 
[[Category:SPO600]]
 
[[Category:SPO600]]
{{Admon/important|Backup Your Data|These computers are NEVER backed up. Please save all important files on other storage. '''These machines may fail, be removed or be reinstalled at any time.'''}}
+
<!-- {{Admon/important|Backup Your Data|These computers are NEVER backed up. Please save all important files on other storage. '''These machines may fail, be removed, be upgraded, or be reinstalled at any time.'''}}
In [[SPO600]], remote access to servers is provided for learning and project work. It is recommended that you also set up [[SPO600 Host Setup|a personal Linux system]].
+
In [[SPO600]], remote access to servers is provided for learning and project work. It is recommended that you also set up [[SPO600 Host Setup|a personal Linux system]]. -->
  
  
 
== Preparatory Steps ==
 
== Preparatory Steps ==
  
In order to gain access to these computers, you must send an [[SSH]] key to your [[User:Chris Tyler|professor]]. Please follow these instructions exactly:
+
In order to gain access to these computers, you must send an [[SSH]] key to your [[User:Chris Tyler|professor]]. <!-- Please follow these instructions exactly:
  
 
# Follow the steps outlined under [[SSH#Using_Public_Keys_with_SSH|Using Public Keys with SSH]] to create your key.
 
# Follow the steps outlined under [[SSH#Using_Public_Keys_with_SSH|Using Public Keys with SSH]] to create your key.
 
# Copy the public key (<code>id_rsa.pub</code> or <code>id_dsa.pub</code>) to a file named <code>''yourUserId''.pub</code> -- for example, if your chosen user ID is "jldoe", save the key in the file <code>jdoe.pub</code> using a command such as: <code>cp ~/.ssh/id_rsa.pub ''jdoe''.pub</code>
 
# Copy the public key (<code>id_rsa.pub</code> or <code>id_dsa.pub</code>) to a file named <code>''yourUserId''.pub</code> -- for example, if your chosen user ID is "jldoe", save the key in the file <code>jdoe.pub</code> using a command such as: <code>cp ~/.ssh/id_rsa.pub ''jdoe''.pub</code>
# Attach that file to an e-mail message and send it to [mailto:chris.tyler@senecacollege.ca chris.tyler@senecacollege.ca] with the subject line "SPO600 Key".
+
# Attach that file to an e-mail message and send it to [mailto:chris.tyler@senecacollege.ca chris.tyler@senecacollege.ca] with the subject line "SPO600 Key". -->
  
 
An account will be created within a few work days of sending the key.
 
An account will be created within a few work days of sending the key.
  
 
{{Admon/tip|Check Your Key!|Your professor uses an automated script to create accounts, so the key must be valid, in the OpenSSH format, and correctly named in order to work successfully.}}
 
{{Admon/tip|Check Your Key!|Your professor uses an automated script to create accounts, so the key must be valid, in the OpenSSH format, and correctly named in order to work successfully.}}
 +
  
 
== Available Servers ==
 
== Available Servers ==
  
{{Admon/important|Changes for Fall 2019|The server configuration for Fall 2019 has changed -- previous mentions of these systems by name may have referred to different hardware. Note that additional servers may be added as the semester proceeds.}}
+
<!-- {{Admon/important|Content being Updated|This page is in the process of being updated from a previous semester's content. The SPO600 servers will be set up in a new configuration later this semester, and this information will be updated. Do not rely on this information until this warning is removed.}}
=== AArch64: aarchie ===
+
 
 +
{{Admon/important|Server Changes|The server configurations have changed several times -- previous mentions of these systems by name may have referred to different hardware. Note that servers may be added or removed as the semester proceeds.}} -->
 +
 
 +
The names of servers within CDOT are based on the names of countries. There is no significance to the country names.
  
<!-- The current, main [[ARMv8]] AArch64 system is known as '''aarchie''' or '''archie'''. This is a system that is currently located inside the [[EHL]]. To connect to this system, you have to go through the EHL gateway on port 2200.
+
=== AArch64: israel.cdot.systems ===
 +
 
 +
A main AArch64 system is available, known as ''israel''. This machine has a lot of mid-range cores. You can access this system at the hostname israel.cdot.systems; if you're using a command-line ssh system, you can access aarchie with a command such as this:
 +
 
 +
ssh ''username''@israel.cdot.systems
 +
<!-- === AArch64: bbetty ===
 +
 
 +
Another type AArch64 system is available as ''bbetty''. This machine has a moderate number of low-medium cores. This is a system that is currently located inside the [[EHL]]. To connect to this system, you have to go through the EHL gateway on port 2200.
  
 
If you're using a command-line ssh system, you can issue a command such as this:
 
If you're using a command-line ssh system, you can issue a command such as this:
Line 27: Line 38:
 
  ssh -p 2200 ''username''@ehl.cdot.systems
 
  ssh -p 2200 ''username''@ehl.cdot.systems
  
Two secondary AArch64 systems have been added, known as ''bbetty'' (or ''betty'') and ''ccharlie'' (or ''charlie''). These systems are also located inside the [[EHL]]. Bbetty has 16GB of RAM and 200GB of space in <code>/home</code>, while ccharlie has 8GB of RAM and 40GB of space in <code>/home</code>.
 
  
Bbetty is accessed on port 2202:
+
=== AArch64: ccharlie ===
  
ssh -p 2202 ''username''@ehl.cdot.systems
+
Another AArch64 system similar to bbetty is named ''ccharlie''. This is a system that is currently located inside the [[EHL]]. To connect to this system, you have to go through the EHL gateway on port 2205.
  
And ccharlie is accessed on port 2205:
+
If you're using a command-line ssh system, you can issue a command such as this:
  
 
  ssh -p 2205 ''username''@ehl.cdot.systems
 
  ssh -p 2205 ''username''@ehl.cdot.systems
  
An additional AArch64 system is also available, known as ''ddouglas''. This system is:
 
  
ssh ''username''@ddouglas.cdot.systems -->
+
=== AArch64: israel ===
An AArch64 system is available, known as "aarchie". You can access this system at the hostname aarchie.cdot.systems; if you're using a command-line ssh system, you can access aarchie with a command such as this:
 
  
ssh ''username''@aarchie.cdot.systems
+
A different AArch64 system is ''israel''. This machine has a good number of mid-level cores. This system is located outside of the EHL and can be reached directly:
  
=== x86_64: xerxes ===
+
ssh ''username''@israel.cdot.systems
 
+
-->
The x86_64 server system is known as ''xerxes''. If you're using a command-line ssh system, you can access xerxes with a command such as this:
 
  
ssh ''username''@xerxes.cdot.systems
+
=== x86_64: portugal.cdot.systems ===
  
<!--The second x86_64 server is known as ''yaggi'' and can be accessed with:
+
The x86_64 server system is known as ''portugal''. If you're using a command-line ssh system, you can access xerxes with a command such as this:
  
  ssh ''username''@yaggi.cdot.systems
+
ssh ''username''@portugal.cdot.systems
-->
 
  
 
== Simplified SSH Access ==
 
== Simplified SSH Access ==
  
If you're using OpenSSH (the ssh client used on most Linux systems and other platforms), you can simplify complex ssh command lines by placing host connection details in the file <code>~/.ssh/config</code>:
+
If you're using OpenSSH (the ssh client used on most Linux systems and other platforms), you can simplify ssh command lines by placing host connection details in the file <code>~/.ssh/config</code>:
  
Host "aarchie"
+
<!-- Host "aarchie"
 
         hostname "ehl.cdot.systems"
 
         hostname "ehl.cdot.systems"
 
         user "YourUserID"
 
         user "YourUserID"
Line 77: Line 83:
 
         hostname "xerxes.cdot.systems"
 
         hostname "xerxes.cdot.systems"
 
         user "YourUserId"
 
         user "YourUserId"
 +
 +
Host "aarchie"
 +
        hostname "aarchie.cdot.systems"
 +
        user "YourUserID"
 +
 +
Host "bbetty"
 +
        hostname "ehl.cdot.systems"
 +
        user "YourUserID"
 +
        port 2200
 +
 +
Host "ccharlie"
 +
        hostname "ehl.cdot.systems"
 +
        user "YourUserID"
 +
        port 2205
 +
-->
 +
 +
Host "portugal"
 +
        hostname "portugal.cdot.systems"
 +
        user "YourUserID"
 +
 +
Host "israel"
 +
        hostname "israel.cdot.systems"
 +
        user "YourUserID"
 +
 +
<!-- Host "xerxes"
 +
        hostname "xerxes.cdot.systems"
 +
        user "YourUserID"
 +
-->
  
 
Once you have added these lines (inserting your user ID where appropriate) and set the permission on that file (<code>chmod 0600 ~/.ssh/config</code>) you can use these commands to access the servers:
 
Once you have added these lines (inserting your user ID where appropriate) and set the permission on that file (<code>chmod 0600 ~/.ssh/config</code>) you can use these commands to access the servers:
  
  ssh aarchie
+
  ssh israel
  ssh bbetty
+
   
ssh ccharlie
+
  ssh portugal
  ssh xerxes
 
  
 
You can similarly configure simplified access in most other SSH client programs.
 
You can similarly configure simplified access in most other SSH client programs.
  
  
== SSH Access from Other Client Systems ==
+
== Multiuser Access ==
 +
 
 +
Remember that these machines are multi-user systems. Use the <code>w</code> or <code>who</code> commands to see who else is using them; you can also try using the <code>write</code> command to communicate with another user if required.
 +
 
 +
 
 +
== Passwords ==
  
If you wish to access the servers from additional computers, you can append the SSH public keys from those computers to the <code>~/.ssh/authorized_keys</code> file.
+
Your password on each of these systems has been set to a random string (different on each host). You can find out the original random password by viewing the file <code>~/password.txt</code> and you can change the password with the <code>passwd</code> command. Your password is used for sudo access (see the next section).
  
  
Line 101: Line 139:
 
{{Admon/caution|Danger! Use Superuser privilege at your Own Risk.|Note that the use of the superuser account via <code>sudo</code> removes almost all restrictions on what you can do. It is easily possible for you to completely destroy the operating system! Take your time, double-check your commands, and if in doubt, ask. Be aware that your actions may affect other users and vice-versa.}}
 
{{Admon/caution|Danger! Use Superuser privilege at your Own Risk.|Note that the use of the superuser account via <code>sudo</code> removes almost all restrictions on what you can do. It is easily possible for you to completely destroy the operating system! Take your time, double-check your commands, and if in doubt, ask. Be aware that your actions may affect other users and vice-versa.}}
  
{{Admon/caution|Do Not Build or Install Software Except Via RPM (dnf/yum)|Do not build or install software as the root user (using <code>sudo</code>), except in RPM form using the <code>dnf</code> or <code>yum</code> commands. Building or installing software as root may overwrite system files and be very difficult to track down.<br /><br />It is OK to install software into your own directories (e.g., <code>~/bin</code> or <code>~/local</code>), which can be done without root privilege.}}
+
{{Admon/caution|DO NOT Build or Install Software as Root except via RPM (dnf/yum) or DEB (apt)|Do not build or install software as the root user (using <code>sudo</code>), except in RPM or DEB form using the <code>dnf</code>/<code>yum</code> or <code>apt</code> commands (as appropriate to the system). Building or installing software as root may overwrite system files and be very difficult to track down.<br /><br />It is OK to install software into your own directories (e.g., <code>~/bin</code> or <code>~/local</code>), which can be done without root privilege.}}
  
 
In order to use <code>sudo</code>, you will need to know your password. An initial random password is provided in the file <code>~/password.txt</code> (note that your password will be different on each server). Feel free to change this with the <code>passwd</code> command -- not by editing the file, which is provided only for your information!
 
In order to use <code>sudo</code>, you will need to know your password. An initial random password is provided in the file <code>~/password.txt</code> (note that your password will be different on each server). Feel free to change this with the <code>passwd</code> command -- not by editing the file, which is provided only for your information!
  
  
== Multiuser Access ==
+
== SSH Access from Other Client Systems ==
 +
 
 +
If you wish to access the servers from additional computers, you can append the SSH public keys from those computers to the <code>~/.ssh/authorized_keys</code> file. Alternately, you can copy the private key from one client system to another (e.g., your laptop to your desktop).
 +
 
 +
 
 +
== OS Versions ==
  
Remember that these machines are multi-user systems. Use the <code>w</code> or <code>who</code> commands to see who else is using them; you can also try using the <code>write</code> command to communicate with another user if required.
+
The current servers are both running Fedora 35 and will be updated from time to time. The machines may not be updated at the same time, so the versions of software may vary slightly. The kernel versions may also vary between the systems because of kernel hardware support.
  
  
Line 122: Line 165:
 
# If your SSH public key is not named <code>~/.ssh/id_rsa</code>, your SSH client may not automatically find it. You can specify the identity (private key) file using the <code>-i</code> argument to the SSH command.}}
 
# If your SSH public key is not named <code>~/.ssh/id_rsa</code>, your SSH client may not automatically find it. You can specify the identity (private key) file using the <code>-i</code> argument to the SSH command.}}
  
With other SSH clients:
+
==== Debugging SSH Connection Problems ====
# Your key must be in OpenSSH format when you send it to your professor; this format is used by the default SSH client on Mac OS/X and Linux as well as PuTTY. If it is in SSH2 format, used by some other client programs, you can convert it with this command on a Linux system with OpenSSH (such as Matrix):
 
ssh-keygen -i -f ~/.ssh/''SSH2_PUBLIC_KEY_FILE''.pub > ~/.ssh/''OPENSSH_PUBLIC_KEY_FILE''.pub
 
  
 +
===== Situation 1: The SSH client asks you for a passphrase =====
 +
 +
The passphrase is the one you provided when you created your SSH keys. You must remember this passphrase in order to successfully unlock your private key. If you do not remember your passphrase, you will need to create a new pair of keys and re-send the public key to your professor:
 +
# Create the keys with <code>ssh-keygen -t ed25591</code>
 +
# Copy the public key (which by default will be named <code>~/.ssh/id_ed25519.pub</code>) to a file named <code>'''UserId'''.pub</code> where '''UserId''' is your Seneca User ID.
 +
# Attach that file to an e-mail message and send it to your professor.
 +
 +
===== Situation 2: The SSH client asks you for a password =====
 +
 +
The password is for the remote system, but the SSH client will only ask you for a password if it is unable to authenticate using your keys. If that is the case, then one of your keys is corrupted, missing, has the wrong permission, or can't be found by the SSH client.
 +
# If you're using OpenSSH, try using the <code>-i</code> argument to tell the client which private key identity file to use: <code>ssh -i /path/to/ssh/PrivateKey ...</code>
 +
# Check the permissions on the private key and the directory holding the private key.
 +
# If necessary, generate a new key and send it to your professor (see the previous section).
 +
 +
===== Getting Verbose Output =====
 +
 +
To see what the OpenSSH client program is doing, you can use the <code>-v</code> (verbose) argument, up to three times: <code>ssh -vvv ...</code>
 +
 +
By reading through the output carefully, you can see what the OpenSSH client program is doing, and address any problems that arise (such as permission or file naming issues).
  
 
== Disconnect/Reconnect Ability ==
 
== Disconnect/Reconnect Ability ==
  
 
The [[Screen Tutorial|screen]] utility provides disconnect/reconnect capability, which is very useful for unstable network connections, long interactive operations, and changing your work location.
 
The [[Screen Tutorial|screen]] utility provides disconnect/reconnect capability, which is very useful for unstable network connections, long interactive operations, and changing your work location.
 +
 +
Other programs such as tmux provide similar capability.
 +
 +
For graphical disconnect/reconnect capability, consider using VNC.

Revision as of 17:16, 7 March 2022


Preparatory Steps

In order to gain access to these computers, you must send an SSH key to your professor.

An account will be created within a few work days of sending the key.

Idea.png
Check Your Key!
Your professor uses an automated script to create accounts, so the key must be valid, in the OpenSSH format, and correctly named in order to work successfully.


Available Servers

The names of servers within CDOT are based on the names of countries. There is no significance to the country names.

AArch64: israel.cdot.systems

A main AArch64 system is available, known as israel. This machine has a lot of mid-range cores. You can access this system at the hostname israel.cdot.systems; if you're using a command-line ssh system, you can access aarchie with a command such as this:

ssh username@israel.cdot.systems

x86_64: portugal.cdot.systems

The x86_64 server system is known as portugal. If you're using a command-line ssh system, you can access xerxes with a command such as this:

ssh username@portugal.cdot.systems

Simplified SSH Access

If you're using OpenSSH (the ssh client used on most Linux systems and other platforms), you can simplify ssh command lines by placing host connection details in the file ~/.ssh/config:


Host "portugal"
        hostname "portugal.cdot.systems"
        user "YourUserID"

Host "israel"
        hostname "israel.cdot.systems"
        user "YourUserID"

Once you have added these lines (inserting your user ID where appropriate) and set the permission on that file (chmod 0600 ~/.ssh/config) you can use these commands to access the servers:

ssh israel

ssh portugal

You can similarly configure simplified access in most other SSH client programs.


Multiuser Access

Remember that these machines are multi-user systems. Use the w or who commands to see who else is using them; you can also try using the write command to communicate with another user if required.


Passwords

Your password on each of these systems has been set to a random string (different on each host). You can find out the original random password by viewing the file ~/password.txt and you can change the password with the passwd command. Your password is used for sudo access (see the next section).


Sudo Access

To perform operations which require privilege, such as installing software, use the sudo command to execute the desired instruction as the root user.

For example, to install the software packaged ncurses-devel, execute: sudo dnf install ncurses-devel on xerxes or sudo yum install ncurses-devel on betty. The commands are different because Xerxes is running Fedora, which has transitioned from the older yum system to dnf, while Betty is running LEAP (based on CentOS), which still uses the older system.

Stop (medium size).png
Danger! Use Superuser privilege at your Own Risk.
Note that the use of the superuser account via sudo removes almost all restrictions on what you can do. It is easily possible for you to completely destroy the operating system! Take your time, double-check your commands, and if in doubt, ask. Be aware that your actions may affect other users and vice-versa.
Stop (medium size).png
DO NOT Build or Install Software as Root except via RPM (dnf/yum) or DEB (apt)
Do not build or install software as the root user (using sudo), except in RPM or DEB form using the dnf/yum or apt commands (as appropriate to the system). Building or installing software as root may overwrite system files and be very difficult to track down.

It is OK to install software into your own directories (e.g., ~/bin or ~/local), which can be done without root privilege.

In order to use sudo, you will need to know your password. An initial random password is provided in the file ~/password.txt (note that your password will be different on each server). Feel free to change this with the passwd command -- not by editing the file, which is provided only for your information!


SSH Access from Other Client Systems

If you wish to access the servers from additional computers, you can append the SSH public keys from those computers to the ~/.ssh/authorized_keys file. Alternately, you can copy the private key from one client system to another (e.g., your laptop to your desktop).


OS Versions

The current servers are both running Fedora 35 and will be updated from time to time. The machines may not be updated at the same time, so the versions of software may vary slightly. The kernel versions may also vary between the systems because of kernel hardware support.


Backup Your Accounts

These accounts are never backed up, and the machines may fail, lose data, or be reinstalled without warning at any time. Please back up your work frequently by copying it to another system or storage device.


Common SSH Problems

With the OpenSSH client:

  1. Your ssh private key must be in your ~/.ssh directory (which must have 0700 permission) and the private key file must have 0600 permissions -- no more and no less.
  2. If your SSH public key is not named ~/.ssh/id_rsa, your SSH client may not automatically find it. You can specify the identity (private key) file using the -i argument to the SSH command.}}

Debugging SSH Connection Problems

Situation 1: The SSH client asks you for a passphrase

The passphrase is the one you provided when you created your SSH keys. You must remember this passphrase in order to successfully unlock your private key. If you do not remember your passphrase, you will need to create a new pair of keys and re-send the public key to your professor:

  1. Create the keys with ssh-keygen -t ed25591
  2. Copy the public key (which by default will be named ~/.ssh/id_ed25519.pub) to a file named UserId.pub where UserId is your Seneca User ID.
  3. Attach that file to an e-mail message and send it to your professor.
Situation 2: The SSH client asks you for a password

The password is for the remote system, but the SSH client will only ask you for a password if it is unable to authenticate using your keys. If that is the case, then one of your keys is corrupted, missing, has the wrong permission, or can't be found by the SSH client.

  1. If you're using OpenSSH, try using the -i argument to tell the client which private key identity file to use: ssh -i /path/to/ssh/PrivateKey ...
  2. Check the permissions on the private key and the directory holding the private key.
  3. If necessary, generate a new key and send it to your professor (see the previous section).
Getting Verbose Output

To see what the OpenSSH client program is doing, you can use the -v (verbose) argument, up to three times: ssh -vvv ...

By reading through the output carefully, you can see what the OpenSSH client program is doing, and address any problems that arise (such as permission or file naming issues).

Disconnect/Reconnect Ability

The screen utility provides disconnect/reconnect capability, which is very useful for unstable network connections, long interactive operations, and changing your work location.

Other programs such as tmux provide similar capability.

For graphical disconnect/reconnect capability, consider using VNC.