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title = "FAQ"
description = "HCC Frequently Asked Questions"
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- [I have an account, now what?](#i-have-an-account-now-what)
- [How do I change my password?](#how-do-i-change-my-password)
- [I forgot my password, how can I retrieve it?](#i-forgot-my-password-how-can-i-retrieve-it)
- [I just deleted some files and didn't mean to! Can I get them back?](#i-just-deleted-some-files-and-didn-t-mean-to-can-i-get-them-back)
- [How do I (re)activate Duo?](#how-do-i-re-activate-duo)
- [How many nodes/memory/time should I request?](#how-many-nodes-memory-time-should-i-request)
- [I am trying to run a job but nothing happens?](#i-am-trying-to-run-a-job-but-nothing-happens)
- [I keep getting the error "slurmstepd: error: Exceeded step memory limit at some point." What does this mean and how do I fix it?](#i-keep-getting-the-error-slurmstepd-error-exceeded-step-memory-limit-at-some-point-what-does-this-mean-and-how-do-i-fix-it)
- [I want to talk to a human about my problem. Can I do that?](#i-want-to-talk-to-a-human-about-my-problem-can-i-do-that)

---

#### I have an account, now what?

Congrats on getting an HCC account! Now you need to connect to a Holland
cluster. To do this, we use an SSH connection. SSH stands for Secure
Shell, and it allows you to securely connect to a remote computer and
operate it just like you would a personal machine.

Depending on your operating system, you may need to install software to
make this connection. Check out on Quick Start Guides for information on
how to install the necessary software for your operating system

- [For Mac/Linux Users]({{< relref "for_maclinux_users" >}})
- [For Windows Users]({{< relref "for_windows_users" >}})

#### How do I change my password?

#### I forgot my password, how can I retrieve it?

Information on how to change or retrieve your password can be found on
the documentation page: [How to change your
password]({{< relref "/accounts/how_to_change_your_password" >}})


All passwords must be at least 8 characters in length and must contain
at least one capital letter and one numeric digit. Passwords also cannot
contain any dictionary words. If you need help picking a good password,
consider using a (secure!) password generator such as
[this one provided by Random.org](https://www.random.org/passwords)

To preserve the security of your account, we recommend changing the
default password you were given as soon as possible.

#### I just deleted some files and didn't mean to! Can I get them back?

That depends. Where were the files you deleted?

**If the files were in your $HOME directory (/home/group/user/):** It's
possible.

$HOME directories are backed up daily and we can restore your files as
they were at the time of our last backup. Please note that any changes
made to the files between when the backup was made and when you deleted
them will not be preserved. To have these files restored, please contact
HCC Support at
{{< icon name="envelope" >}}[hcc-support@unl.edu] (mailto:hcc-support@unl.edu)
as soon as possible.

**If the files were in your $WORK directory (/work/group/user/):** No.

Unfortunately, the $WORK directories are created as a short term place
to hold job files. This storage was designed to be quickly and easily
accessed by our worker nodes and as such is not conducive to backups.
Any irreplaceable files should be backed up in a secondary location,
such as Attic, the cloud, or on your personal machine. For more
information on how to prevent file loss, check out [Preventing File
Loss]({{< relref "preventing_file_loss" >}}).

#### How do I (re)activate Duo?

**If you have not activated Duo before:**

Please stop by
[our offices](http://hcc.unl.edu/location)
along with a photo ID and we will be happy to activate it for you. If
you are not local to Omaha or Lincoln, contact us at
{{< icon name="envelope" >}}[hcc-support@unl.edu] (mailto:hcc-support@unl.edu)
and we will help you activate Duo remotely.

**If you have activated Duo previously but now have a different phone
number:**

Stop by our offices along with a photo ID and we can help you reactivate
Duo and update your account with your new phone number.

**If you have activated Duo previously and have the same phone number:**

Email us at
{{< icon name="envelope" >}}[hcc-support@unl.edu] (mailto:hcc-support@unl.edu)
from the email address your account is registered under and we will send
you a new link that you can use to activate Duo.

#### How many nodes/memory/time should I request?

**Short answer:** We don’t know.

**Long answer:** The amount of resources required is highly dependent on
the application you are using, the input file sizes and the parameters
you select. Sometimes it can help to speak with someone else who has
used the software before to see if they can give you an idea of what has
worked for them.

But ultimately, it comes down to trial and error; try different
combinations and see what works and what doesn’t. Good practice is to
check the output and utilization of each job you run. This will help you
determine what parameters you will need in the future.

For more information on how to determine how many resources a completed
job used, check out the documentation on [Monitoring Jobs]({{< relref "monitoring_jobs" >}}).

#### I am trying to run a job but nothing happens?

Where are you trying to run the job from? You can check this by typing
the command \`pwd\` into the terminal.

**If you are running from inside your $HOME directory
(/home/group/user/)**:

Move your files to your $WORK directory (/work/group/user) and resubmit
your job.

The worker nodes on our clusters have read-only access to the files in
$HOME directories. This means that when a job is submitted from $HOME,
the scheduler cannot write the output and error files in the directory
and the job is killed. It appears the job does nothing because no output
is produced.

**If you are running from inside your $WORK directory:**

Contact us at
{{< icon name="envelope" >}}[hcc-support@unl.edu] (mailto:hcc-support@unl.edu)
with your login, the name of the cluster you are running on, and the
full path to your submit script and we will be happy to help solve the
issue.

##### I keep getting the error "slurmstepd: error: Exceeded step memory limit at some point." What does this mean and how do I fix it?

This error occurs when the job you are running uses more memory than was
requested in your submit script.

If you specified `--mem` or `--mem-per-cpu` in your submit script, try
increasing this value and resubmitting your job.

If you did not specify `--mem` or `--mem-per-cpu` in your submit script,
chances are the default amount allotted is not sufficient. Add the line

{{< highlight batch >}}
#SBATCH --mem=<memory_amount>
{{< /highlight >}}

to your script with a reasonable amount of memory and try running it again. If you keep
getting this error, continue to increase the requested memory amount and
resubmit the job until it finishes successfully.

For additional details on how to monitor usage on jobs, check out the
documentation on [Monitoring Jobs]({{< relref "monitoring_jobs" >}}).

If you continue to run into issues, please contact us at
{{< icon name="envelope" >}}[hcc-support@unl.edu] (mailto:hcc-support@unl.edu)
for additional assistance.

#### I want to talk to a human about my problem. Can I do that?

Of course! We have an open door policy and invite you to stop by
[either of our offices](http://hcc.unl.edu/location)
anytime Monday through Friday between 9 am and 5 pm. One of the HCC
staff would be happy to help you with whatever problem or question you
have.  Alternatively, you can drop one of us a line and we'll arrange a
time to meet:  [Contact Us](https://hcc.unl.edu/contact-us).