# six demon bag

Wind, fire, all that kind of thing!

2017-08-07

## Generate a Solr Password Hash

Recent versions of Solr allow restricting access via authentication and authorization plugins, for instance the basic authentication plugin. The documentation shows an example security.json that you can upload into Zookeeper (assuming that you're running SolrCloud).

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Posted 22:15 [permalink]

2017-08-04

## Useful settings for grub on Debian

### Boot a kernel just once

If you want to test a new kernel without having access to the console you need to make sure that the system comes back up with the old kernel if the new one panics. Add a setting panic=2 to the kernel commandline in /etc/default/grub to have the system automatically reboot in case of a kernel panic, and tell grub to boot a saved kernel by default:

GRUB_DEFAULT="saved"
GRUB_CMDLINE_LINUX="panic=2"


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Posted 01:45 [permalink]

## IPMI interface network configuration from Linux

Load the relevant modules, either via modprobe or by entering them into /etc/modules (so they're loaded automatically on the next system startup).

modprobe ipmi_devintf
modprobe ipmi_si


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Posted 00:36 [permalink]

2017-04-01

## Reset VSS Writers

VSS writers are application-specific components for Microsoft's Volume Shadow Copy Service, which ensure the consistency of application data when a shadow copy is created. That's quite useful for creating consistent backups of a system. However, some of these writers go into error states more or less frequently. And Microsoft did not deem it necessary to document how to reset writers without rebooting the entire system (or at least I didn't manage to find that piece of information).

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Posted 20:41 [permalink]

2017-03-21

## Verifying checksums on Windows systems - correctly

Posted here, since the Fedora people apparently can't be bothered to fix their documentation.

In January 2016 I came across this question on StackOverflow, asking about an OutOfMemory error when validating the SHA256 checksum of a Fedora ISO image. The Fedora documentation suggested reading the full file and then calculating the checksum from the bytes:

$sha256.ComputeHash([System.IO.File]::ReadAllBytes("$PWD\$image"))  Why anyone would even want to read an entire ISO image into memory for a checksum calculation is beyond me. The recommended way of doing this is to open the file as a stream and calculate the checksum on that stream: See more ... Posted 00:53 [permalink] 2016-12-17 ## Disable AVAHI Daemon on Debian To prevent the AVAHI daemon on Debian systems from running without actually uninstalling the package avahi-daemon or touching the runlevels do this: touch /var/run/avahi-daemon/disabled-for-unicast-local sed -i 's/^#\?$$AVAHI_DAEMON_DETECT_LOCAL$$=.*/\1=1/' /etc/default/avahi-daemon service restart avahi-daemon  I've seen people suggest putting a line exit 0 into /etc/default/avahi-daemon, but I wouldn't recommend that, because it would prevent not only starting the daemon, but also stopping it. Posted 15:35 [permalink] 2016-09-01 ## Forwarding JVM Garbage Collector Logs Recently I was tasked with forwarding logs to a central log server - in this case JVM garbage collector logs from Solr instances. Normally not a big deal. Configure log rotation (to avoid filling the disk), then have rsyslog read the active log file via an imfile input. Sounds simple, right? Until you realize that JVM log rotation marks the active log with the extension .current and rotates that extension instead of actually rotating the logs. See more ... Posted 23:27 [permalink] 2016-04-12 ## Spark Workers Not Starting If you're using Apache Spark and run into an issue where your workers fail to start, make sure that the workers use the same SPARK_MASTER_IP value that was used when starting the master. You can see it in the top left corner of the master's web interface: See more ... Posted 21:37 [permalink] 2016-02-27 ## VBSdoc - A VBScript API Documentation Generator API documentation is nice, and being able to generate it from the code is even nicer. However, unlike Perl, Python, Java, or several other languages, VBScript doesn't have a feature or tool that supports this. Which kinda sucks. I tried VBDOX, but didn't find usability or results too convincing. I also tried doxygen by adapting Basti Grembowietz' Visual Basic doxygen filter. However, doxygen does a lot of things I don't actually need, and I didn't manage to make it do some of the things I do need. Thus I ended up writing my own VBScript documentation generator. See more ... Posted 19:15 [permalink] 2016-01-04 ## Cannot delete my own scheduled task Recently I noticed that I was no longer able to delete scheduled tasks on my Windows 7 test box, even though I created them myself. Deletion attempts failed with the following error: The user account does not have permission to delete this task. Deleting my own tasks works fine in a vanilla install of Windows 7 SP1, so the issue must have been introduced by some update along the way. I had to modify the permissions on C:\Windows\System32\Tasks to get it to work again: icacls "C:\Windows\System32\Tasks" /grant "Authenticated Users":(RD)  Granting "list folder/read data" on the folder itself was sufficient, since the task files are owned by the user creating them and the CREATOR OWNER principal has full access to subfolders and files. Posted 19:51 [permalink] 2015-12-31 ## Barracuda Backup Agent for Linux Unattended Installation Barracuda Networks provide agents for their backup appliance for various operating systems. Unfortunately the Linux agent (unlike the Windows agent) does not come with an option for a silent installation, and it doesn't look like the vendor can be bothered to do anything about it. Instead of being able specify a path on the commandline (or at least force a silent installaton to the default path) you're always prompted for the path where the agent should be installed: /tmp # tar xzf barracuda_backup_agent-x.x.x.tar.gz /tmp # cd barracuda_backup_agent-x.x.x /tmp/barracuda_backup_agent-x.x.x # ./install Please choose an installation path, or press enter for default. [/usr/local/barracuda/bbs]: _ See more ... Posted 01:13 [permalink] 2015-12-30 ## Save and Restore a DataTable If you have a DataTable object in PowerShell and you want to persist that object as a file (and restore it back to a DataTable object sometime later) the naïve approach would be to export the (tabular) data to a (tabular) CSV: $dt | Export-Csv -Path 'C:\path\to\table.csv' -NoType


However, the problem with this approach is that you lose the type information for the columns of the datatable (the only type information saved by the Export-Csv cmdlet is about the type of the objects representing the rows). Also, there's no simple way to restore the CSV back to a datatable.

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Posted 17:01 [permalink]

2015-09-29

## Hyper-V Live Migration fails with error 0x80090303

If you have a live migration fail with an error like this:

Live migration of 'Virtual Machine VM01' failed.

Virtual machine migration operation for 'scvmm_instance' failed at migration source 'Hypervisor01'. (Virtual machine ID XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX)

The Virtual Machine Management Service failed to establish a connection for a Virtual Machine migration with host 'Hypervisor02': The specified target is unknown or unreachable (0x80090303).

The Virtual Machine Management Service failed to authenticate the connection for a Virtual Machine migration at the source host: The specified target is unknown or unreachable (0x80090303).

check that both hypervisors have the required SPNs registered.

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Posted 17:22 [permalink]

2015-06-14

## Querying DB2 Backups in TSM Fails with Return Code 106

On one of my servers a query for DB2 backups in TSM (db2adutl query full db DBNAME) failed with the following error:

Error: Initialize environment failed with TSM return code 106

As per dsmrc.h return code 106 indicates a permission problem:

#define DSM_RC_ACCESS_DENIED       106 /* denied due to improper permission */


which was weird, since the user in question is a member of the DB2ADMNS group that is supposed to have all required permissions.

See more ...

Posted 23:40 [permalink]

2015-06-07

## Using the DB2 Command Line Processer from PowerShell

Even for DB2 10.5 the official documentation says to use the db2cmd command for a Command Line Processor enabled environment on Windows:

On Windows operating systems, db2cmd command opens the CLP-enabled DB2® window, and initializes the DB2 command line environment.

However, being able to use PowerShell instead of db2cmd would be much nicer, since the former is far more versatile in practically every respect (control structures, output processing, file handling, etc.).

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Posted 01:38 [permalink]

2015-03-18

## Now With a Tag Cloud

As you can see my blog now has a fancy tag cloud. This is my first attempt at a Blosxom plugin, and I'm quite proud of it. *^_^*

I've already been using Gregor Rayman's keywords plugin for auto-generating the keywords meta tag, so I wanted something based on that rather than having to use an additional tag line as required for the tagcloud plugin. The tag cloud is generated from the keywords with the HTML::TagCloud Perl module, and I'm using Fletcher Penney's find plugin for linking to blog posts that match the respective keyword. The find plugin also gives me a nice search box (another thing I've been wanting to add for a while). Sweet.

Download: wordcloud-0.1

The keywords and find plugins are included, since their homepages don't seem to be online anymore. Also included is a patch for HTML::TagCloud that allows for case-insensitive sorting.

Posted 20:37 [permalink]

2015-03-12

## Repairing a Suspect msdb Database

Sometimes a situation arises where an SQL Server instance comes back up with a database tagged as "suspect". Apparently there is a number of possible causes for this, like transaction log corruption, insufficient memory or disk space, or unexpected shutdowns due to hardware or power failure. In our case the reason was probably a hardware failure, since the database resides on an iSCSI volume, and we were making changes to our iSCSI network. And to make things a little bit more interesting, our msdb database just had to be among the affected databases.

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Posted 19:07 [permalink]

## Transfer Active Directory Site Subnets

A while ago I had to take a couple hundred subnets (don't ask) of an Active Directory site in one domain and re-create them in another domain. Doing that manually would've been a real pain. But if you export the subnets to a file the list can easily be transferred to the other domain and imported there.

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Posted 17:42 [permalink]

2015-03-09

## Drag & Drop in a PowerShell GUI

For a little PowerShell GUI (using Windows Forms) the requirement to drag & drop files into a listbox came up. Some quick googling showed several articles (like this one) suggesting to set AllowDrop = \$true and add a handler for the DragEnter event.

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Posted 19:18 [permalink]

2015-02-22

## NTP "Leap not in sync"

Today I had a rather curious problem on my fileserver. I noticed that its system time was behind the clock, but when I tried to manually synchronize it with my timeserver, ntpdate failed with the error message "Leap not in sync".

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Posted 21:40 [permalink]