Difference between revisions of "Nebula"

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On any unix terminal emulator, enter the command:
On any unix terminal emulator, enter the command:
ssh <userName>@nebula.srv.hacdc.org -p ####
ssh <userName>@nebula.srv.hacdc.org -p 2222
On other platforms, try applications like [http://www.chiark.greenend.org.uk/~sgtatham/putty/ PuTTY] with similar settings. Local connections (within HacDC's network) will need to use IP address .
On other platforms, try applications like [http://www.chiark.greenend.org.uk/~sgtatham/putty/ PuTTY] with similar settings. Local connections (within HacDC's network) will need to use IP address .

Revision as of 18:01, 12 March 2017

Simple project server, likely successor to Shimmer. Emphasis on high-availability.

For discussion purposes, server is nicknamed "Nebula".


  • Matthew "mirage335" Hines


#hacdc on irc.freenode.net (or via chat.hacdc.org)


On any unix terminal emulator, enter the command:

ssh <userName>@nebula.srv.hacdc.org -p 2222

On other platforms, try applications like PuTTY with similar settings. Local connections (within HacDC's network) will need to use IP address .


Consider using Nebula as a fallback for mission-critical lightweight services hosted on Starlight (eg. MediaWiki, git, etc).


Routinely important commands unique to this server documented as follows.

Root (Admin)


  • apt-get install xen-linux-system xen-tools git sudo
  • dpkg-divert --divert /etc/grub.d/08_linux_xen --rename /etc/grub.d/20_linux_xen
  • Installation of hostedXen .


  • ./hxNewUser <userName> # Creates user account with default Xen VM and permissions.
  • ./hxDelUser <userName> # Deletes user account, associated VMs, and associated Xen permissions.
  • ./hxNewVM <userName> <VM_Number> <dist> # Creates VM accessible to non-root user <userName> .


Through normal reboots, host will suspend/resume any guest VMs. If that is insufficient, the correct way to enable autostarting is through the xm command, documented as method 2 here.



  • iptables -t nat -L -n -v #Lists port forwarding rules.
  • iptables -t nat -F #Deletes port forwarding rules.
  • iptables -D PREROUTING 1 #Deletes port forwarding rule.


/sbin/iptables -P FORWARD ACCEPT
/sbin/iptables --table nat -A POSTROUTING -o eth0 -j MASQUERADE

/sbin/iptables -t nat -A PREROUTING -p tcp -i eth0 --dport 20283 -j DNAT --to


Package iptables-persistent has been installed. Upon installation, existing iptables rules were saved. Edit /etc/iptables/rules.v4 .


Please note, your virtual machine has most likely been created with a root password identical to your account, but will require, through the console, manually enabling root SSH login.


List Xen VMs created for you.

cat ~/xenList


Start Xen VM, and launch console.

sudo /usr/sbin/xl create -c /etc/xen/<name>.cfg     #Escape with Ctrl+] .

Just start Xen VM. Useful if planning to interact through other means (ie. network).

sudo /usr/sbin/xl create /etc/xen/<name>.cfg


Yes, really, hard shutdown is termed "destroy". Don't worry, not synonymous with "delete".

sudo /usr/sbin/xl destroy <name>


Opens the console of running VM <name> .

sudo /usr/sbin/xl console <name>     #Escape with Ctrl+] .


Dell 1850

  • CPU - Dual Processor, Quad-Core
  • RAM - 2GB ECC, future upgrade to 16GB
  • HDD - 100GB SAS RAID1
  • Hostname - HacDC-shared-m335-3
  • FQDN - HacDC-shared-m335-3.srv.hacdc.org

Redundancy (RAID)

Root filesystem is comprised of two approximately 100GB HDDs.

Chasis supports second redundant power supply, to be installed when available.




HacDC members with a demonstrable need or willingness to manage non-root users may be given root access. Imperative that root users do not jeopardize uptime.


All HacDC members are welcome to non-root shell accounts, directly provided by the server.


All HacDC members are welcome to Xen Virtual Machines. Resources, including CPU, disk space, and external network ports, will be allocated on an as-needed first-come-first-serve basis.

Root users, please use the provided hostedXen scripts. Following the naming conventions set therein helps account for which resources belong to whom.


Internal server email will notify users, if feasible, on the following schedules, subject to change.

  • Three days before planned downtime exceeding one hour.
  • One week before planned permanent downtime (obsolescence).

Forwarding to another email address is possible with the following command.

echo 'person@mail.com' > ~/.forward


  • Up to three months before removal of ex-member accounts. Exceptions on a case-by-case basis.
  • Compromised accounts will be immediately removed or disabled as discovered.
  • Excessive resource use, including disk space consumption, may be terminated, particularly if account holder is not responsive to inquiries.


  • Failure of both disks will result in unrecoverable loss of data on this server.
  • Removed accounts or terminated services may result in immediate, permanent deletion.
  • As array repair procedures are rarely done, catastrophic mistakes are possible.


Machine is security is not especially tight. Sysadmins may investigate possible abuse. Privacy may exist, but is not a reasonable expectation.



Vast quantities of disk space are available. Still, please be considerate, and understand that on-mission HacDC activities may be given priority.


Sharing of account resources is permitted, however, additional resources will be allocated according to individual member needs for specific purposes. As a reminder, compromised accounts will be immediately removed or disabled as discovered.


Although HacDC has a high-capacity 175/15Mbit link, it is shared with other tenants. Please be courteous. If internet bandwidth use is required for downloading large files, between 2200EDT and 0600EDT is best.

Hard bandwidth limits have not been set to ease administration of local file servers. However, please configure applications to limit maximum bandwidth use where possible, particularly for web servers.

  • NOTE: If your bandwidth use is too high during normal hours, the church administrator will cut bandwidth available to the whole subnet and will call mirage335, juri_, Ethan Waldo, or other admin team members to resolve the issue (no one will be happy).

Special Services


Ports 80/443 are available through reverse proxy. Please setup a relevant domain name (eg. *.member.hacdc.org) through FreeDNS or other service, and contact the HacDC admin team for assistance.


Periodic backup to server Starlight may be performed by admins.


Preferred network names for participating machines and virtual machines.




  • HacDC - Identifies machine as HacDC or HacDC member property on the local network.
  • shared - One of private, restricted, shared. Private = one member only (eg. RasPi). Restricted = limited access (eg. HacDC web server). Shared = shared resources (ie. remote shells).
  • m335 - Abbreviated member name or screen name. Full contact details should be written on the physical machine.
  • 1 - Unique identifier.






  • mirage335 - Local username.
  • 1 - Unique machine identifier.




EST/EDT aka US Eastern, America/NewYork, or "Eastern"


SSH KeepAlive

Due to limited bandwidth, SSH sessions may freeze. To prevent this, consider the following to configuration, appended to client-side ~/.ssh/config .

Host *
  ServerAliveInterval 30


MAW3147NC hard disks are available at reasonable cost from eBay.


No guarantees. Admins are expected to make best efforts toward reliability, security, and privacy. Monitoring may include without limitation system health, resource consumption, and authentication failures, and the like. More intrusive monitoring, such as of user filesystems, should be avoided if possible.

Excepting the case, reasonably requsitioned as a supply, the server is property of mirage335 and Julia Longtin. Administration is at their discretion.

Substantial personal investments were put into this server. Misuse will be taken as a severe disappointment.


Hardware donor.