Jun 3 2020

Open Media Vault admin site not working

I have a NAS running Open Media Vault (OMV) and this week it decided to not display the web front end.

When browsing to http://omvIPaddress I received the below error:

OMV\Exception: Failed to read file ‘/var/cache/openmediavault/cache.omv\controlpanel\login_js.json’ (size=0). in /usr/share/php/openmediavault/json/file.inc:207

To resolve the issue I connected to the NAS using secure shell:

ssh root@ipaddressOfYourNAS and supplied the root password
After authenticating and connecting I ran omv-aptclean and rebooted the server for good measure.

I was able to access the web front end again after running omv-aptclean as per above.


Apr 20 2020

Unable to send mail through specific Send Connector

I’m finding it difficult to give this post a proper heading but hopefully the tags in the post would have led you to the solution of this problem I experienced.

We have a specific Send Connector in Exchange 2016 that sends mail to one of our other companies in a different forest. I noticed that only on one server the queue for mail destined to this domain was queueing. 

The error in the queue destined to the other domain was stating that it failed to connect. I tested with telnet to the VIP IP and could not connect to the VIP on port 25.

After restarting the Transport service and rebooting the server since only this server was experiencing the issue, I found that mail was still stuck in the queue to this VIP.

We checked the F5 and eventually found that I was unable to ping the gateway from my Exchange server but could ping it from my other Exchange nodes.

Changing the gateway to another gateway solved the issue but changing back to the original gateway caused the queue build up again. Scratching our heads that the gateway works for the other nodes.

The solution at the end was to clear the arp cache on the server where the mail was queueing up. From the command prompt I ran arp -a to get the cached entry for the gateway and then ran arp -d to delete the arp cache.

The issue was resolved after we cleared the arp cache from this Exchange node.


Aug 20 2019

Error Installing CentOS 7

I received the error “This program has encountered an unknown error.” When installing CentOS. At the end of the report it had details about RAID and I remembered that the disk was part of a RAID.

To get rid of the RAID config:

  1. Restart the server.
  2. At the menu choose Troubleshooting Choose Rescue a CentOS system.
  3. You will be asked to make a selection, type in 1 and press enter. 
  4. You will see a prompt “Please press return to get a shell.
  5. Press the enter key Under “Rescue Mount” check which disk you need to configure i.e. sdb
  6. Now type: dmraid -E -r /dev/yourDisk i.e. (dmraid -E -r /dev/sda1)
  7. You will be asked if you want to erase “isw”. type y and press enter.
  8. Reboot your server and install CentOS 7

Here’s a video showing the screenshots I took:

 


Aug 20 2019

Moving my server from Windows to Linux

I have moved from Windows to Linux on my laptop and gaming PC (Elementary OS) to be more specific and have not looked back.

My home server was running Windows Home Server 2011 and it seemed like I lost one of my disks with my music on. Windows could not see the disk at all but I could see the disk in the BIOS. I then booted into Linux using a USB thumb drive and managed to access the disk and it’s data so proceded to backup the data.

I then decided to get rid of Windows on my server and move to CentOS 7. I chose CentOS 7 as I am currently studying for my RHCSA

Below is the first video of the series. I stumbled across a few issues which I will be sharing soon.

 


Jul 15 2019

How to install PyQt4 on Elementary OS (Linux)

In this video I show the steps on how to install PyQt 4 on Elementary OS which should work on all Ubuntu based Linux distributions.

I already had PyQt 5 installed but my study guide requires PyQt 4 so I decided to install and run both on my system.

Here’s the steps:

  • Open a terminal and run the below to install PyQt 4
  • sudo apt-get install python3-pyqt4
  • sudo apt-get install libqt4-dev
  • sudo apt-get install python-qt4 qt4-dev-tools python-qt4-dev pyqt4-dev-tools

Here’s a video if that’s more to your liking:


Apr 27 2019

How to make another version of Python the default version in Linux

In this post I show you how to make Python 3.7 the default version of Python on Linux. (This should work on all distributions of Linux).

My default version of Python was Python 2 and I needed to change it to version 3.7. 1.

Steps:

  1. Open your .bashrc file in your home directory using a text editor or the shell.
  2. Add alias python=’/usr/bin/pythonx.x’ to the file and save it. (x.x is your version that you want to be the default)
  3. Logout of your session or reboot your computer, then log back in.
  4. Open the terminal and then type in Python. It should now show you the version that you specified in the .bashrc file


Apr 25 2019

Install Python 3.7 on Elementary OS

In this article and the below video I show you how to install Python 3.7 the easy way on Elementary OS. This works on Pop_OS! and Ubuntu too.

1. Open a terminal
2. type and run: sudo apt update
3. type and run: sudo apt install software-properties-common
4. type and run: sudo add-apt-repository ppa:deadsnakes/ppa
5. Press Enter to add the above repository
6. type and run: sudo apt update
7. type and run: sudo apt install python3.7

You now have Python 3.7 installed


Jul 31 2018

Maximum number of items that can be serialized or deserialized in an object graph is ‘2000000’

You receive the below error when moving a mailbox to another database in Exchange 2013:

Graph error when moving a mailbox

The default limit for the maxItemsInObjectGraph is set to 20000000. The work around that resolved this for me is as per below:

  • Open Notepad and browse to: C:\Program Files\Microsoft\Exchange Server\V15\Bin (or where you installed Exchange).
  • Look for the config file (MsExchangeMailboxReplication.exe.config) and open it.

Hit ctrl + f and search for graph. You will see the below entries.

  • Change the “2” to “3” in order to increase the limit.
  • Restart the Microsoft Exchange Mailbox Replication service on the server you are migrating the mailbox to.
  • Resume the move-request.
  • Change the above back to the previous values and then restart the Microsoft Exchange Mailbox Replication service again.

I managed to complete the mailbox move after running through the above. I’m not 100% sure if this works for Exchange versions older than version 2013 though.







Jan 4 2018

The trust relationship between this workstation and the primary domain failed

I had an issue when trying to logon to one of our servers. After providing my credentials I received the below error.

All we needed to do was to reboot the server and I was able to RDP and login again. What caused the issue is not known as yet.







Jan 2 2018

The InnerException message was ‘Maximum number of items that can be serialized or deserialized in an object graph is ‘2000000’.

This was quite an interesting error for a mailbox I tried to migrate from Exchange 2013 to Exchange Online. The mailbox synced to 95% and I received the below error after I tried completing the batch.

Error details: The formatter threw an exception while trying to deserialize the message: There was an error while trying to deserialize parameter http://tempuri.org/:ISourceFolder_EnumerateChanges2Result. The InnerException message was ‘Maximum number of items that can be serialized or deserialized in an object graph is ‘2000000’.

The key to this error is the object graph limit that is set in the MsExchangeMailboxReplication.exe config file. To resolve the issue do the following:

  1. Logon to your on premises Exchange CAS servers that you use as the proxies for migrating mailboxes to EOL. (In my case this was Exchange 2013)
  2. Open Notepad as an administrator
  3. Browse to C:\Program Files\Microsoft\Exchange Server\V15\Bin (or your Exchange installation path) and open the MsExchangeMailboxReplication.exe config file
  4. Hit ctrl + f in Notepad and search for maxItemsInObjectGraph (there are two entries and I had to change both values)
  5. You want to increase the number in these strings:   <dataContractSerializer maxItemsInObjectGraph=”20000000″/> This is what the original looks like below.
  6. Restart the mailbox replication service on all the servers where you have changed the value.
  7. If the migration failed, then delete the migration job and restart it. You should not have the error again.
  8. Change the strings back to default using the above steps after you migrated the affected mailboxes for which you received the above error.

Here’s what the entries in the config file look like before any changes were made:

 

<behavior name=”MrsProxyServiceBehavior”>
<serviceDebug includeExceptionDetailInFaults=”True” />
<serviceAuthorization serviceAuthorizationManagerType=”Microsoft.Exchange.MailboxReplicationService.MRSProxyAuthorizationManager, Microsoft.Exchange.MailboxReplicationService.ProxyService, Version=15.0.0.0, Culture=neutral, PublicKeyToken=%%%%%%%”/>
<serviceThrottling
maxConcurrentCalls=”200″
maxConcurrentSessions=”200″
maxConcurrentInstances=”200″ />
 <dataContractSerializer maxItemsInObjectGraph=”20000000″/>
</behavior>
</serviceBehaviors>
<endpointBehaviors>
<behavior name=”MrsProxyEndpointBehavior”>
 <dataContractSerializer maxItemsInObjectGraph=”2000000″/>