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guide:cloud:faq

CHPC Cloud Resources

Technical FAQs

1) Do you monitor my VM’s activity?

   Answer: We do not monitor user VM activity.

2) I cannot SSH into my VM which was working fine yesterday, do you know what happened?

   Answer: Please provide us more details about your VM in order to investigate. In the meantime, please
   click on the Instance name in the Compute -> Instances tab, and then click on the Console tab to see
   if there is any error output sent to the console.

If you see messages like below it means that the kernel has hung and you will have to hard reboot the VM using the Actions drop-down menu.

 [ 1920.399095] Not tainted 3.13.0-79-generic #123-Ubuntu
 [ 1920.399559] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 [ 1920.400763] INFO: task apt-check:1286 blocked for more than 120 seconds.
 [ 1920.401360] Not tainted 3.13.0-79-generic #123-Ubuntu
 [ 1920.401820] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 [ 2040.400079] INFO: task rs:main Q:Reg:1061 blocked for more than 120 seconds.
 [ 2040.400697] Not tainted 3.13.0-79-generic #123-Ubuntu
 [ 2040.401132] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
 [ 2040.401883] INFO: task apt-check:1286 blocked for more than 120 seconds.

Basically, add these lines to “/etc/sysctl.conf”:

  vm.dirty_background_ratio = 5 
  vm.dirty_ratio = 10

And then apply them:

  sysctl -p 

A good reading describing these parameters can also be found here: https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performance-vm-dirty_ratio/

3) How can I save the changes I made to my VM, so I can use it later?

  Answer: You can snapshot your instance which saves its state into a new base image that you can use
  later. The snapshot causes the instance to be paused temporarily and it's preferable to not have disk
  activity while doing this, and the snapshot might even fail if the instance has (or had) a lot of data
  written to it since it was started. Please see the User Guide section for more info on how to take a
  snapshot.

4) I attached a large volume to my instance (10 TB), but when I try to format it takes a very long time. What can I do to make this step faster?

Answer: We recommend you format it as XFS and use the “-K” option:

  mkfs.xfs -K /dev/vdb 

In our tests, it took around 3 min to format a 10 TB attached volume.

5) How do I give access to another user to my instance, without giving him access to my SSH private key?

Answer:You should never give another user access to your credentials or private key. Please run the following commands inside your instance in order to create a new user and allow him SSH key-based access to your instance. Replace “username” with your colleague's name.

  sudo adduser username
  sudo usermod -a -G users username
  mkdir /home/username/.ssh/
  chmod 700 /home/username/.ssh/
  chown username:username /home/username/.ssh/
  Obtain the user’s SSH public key and add it to his home directory: /home/username/.ssh/authorized_keys
  chown username:username /home/username/.ssh/authorized_keys

For More Technical Assistance

If you can’t find what you are looking for, please contact our support team. We are working hard to get back to you within 1-2 business days. Submit the ticket at Helpdesk


Billing FAQs

1) I powered off my instance but I was still charged for usage!

   Answer: CHPC charges for resources allocated to the users whether they are actively using them or not.
           The resources you were approved for are reserved for you therefore  you obligated to pay
           for them.
   

2) How often am I billed?

  Answer: CHPC will send out invoices on the 5th of every month for the previous calendar month usage.
          

4) If I have an unpaid invoice, does that unpaid invoice get rolled in to the next months invoice?

  Answer: Yes.

5) Why does my bill fluctuate each month even though I am consuming the same amount of resources each month?

  Answer: We charge for resources used per hour and the number of hours per month vary throughout the
          year (28 days, 30 days, 31 days).

6) Why am I not receiving an invoice?

  Answer: CHPC sends cloud resource usage invoices to all paying users on the 5th of every month.  
  

If you would like to terminate your account please email helpdesk@chpc.ac.za

7) I have a billing related question that is not listed here, help?

Answer: Email helpdesk@chpc.ac.za with your question!

/var/www/wiki/data/pages/guide/cloud/faq.txt · Last modified: 2020/09/11 17:32 by zmtshali