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→Sudo Access
[[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 , 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]].
== 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:
# 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>jldoejdoe.pub</code> using a command such as: <code>cp ~/.ssh/id_rsa.pub ''jldoejdoe''.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".
{{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 ==
{{Admon/important|Server Changes|The server configurations have changed several times changed -- 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.}}
=== AArch64: aarchie ===
A main AArch64 system is available, known as ''aarchie''. This machine has a lot of weak cores. 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:
=== AArch64: aarchie, bbetty, ccharlie ===
If you're using a command-line ssh system, you can issue a command such as this:
ssh -p 2200 ''username''@ehl.cdot.systems
ssh -p 2205 ''username''@ehl.cdot.systems
=== AArch64: israel ===
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:
ssh ''username''@israel.cdot.systems
=== x86_64: xerxes ===
ssh ''username''@xerxes.cdot.systems
== 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>:
hostname "ehl.cdot.systems"
user "YourUserID"
Host "xerxes"
hostname "xerxes.cdot.systems"
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 "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:
ssh bbetty
ssh ccharlie
ssh israel
ssh xerxes
You can similarly configure simplified access in most other SSH client programs.
== SSH Access from Other Client Systems ==
{{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) 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>yumapt</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!
== 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.
== OS Versions ==
Note that the servers may have different operating system releases.
== Backup Your Accounts ==
With other SSH clients:
# 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
Your professor will do this automatically as part of the key processing; however, you will need to manually perform this step for any keys that you append to your <code>~/.ssh/authorized_keys</code> file(s).
== 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.
