0xStubs – Page 2 – System Administration, Reconfigurable Computing and Other Random Topics

Migrating from ownCloud 9.1.6 to Nextcloud 10

June 14, 2017 / By Michael / In System Administration / 3 Comments

If you are stuck with PHP 5.4 (e.g. because you are still running Debian Wheezy) and want to migrate from ownCloud to Nextcloud, you are probably facing a minor issue. Nextcloud 11 and newer require PHP 5.6 so you have to stick to version 10 instead. Nextcloud 10 reached its end-of-life with version 10.0.5, which internally corresponds to ownCloud version 9.1.5. The most recent version of ownCloud 9 is version 9.1.6 though, so when trying to migrate to Nextcloud you will face the following error:

Downgrading is not supported and is likely to cause unpredictable issues (from 9.1.6.2 to 9.1.5.2)

Looking at the git commits between ownCloud 9.1.5 and 9.1.6 shows that there were no changes to the database layout. So, as a workaround, you can just edit your config/config.php and set version to 9.1.5.1 or lower. Afterwards, you should be able to run the normal upgrade procedure.

Using the HackRF One as a wideband spectrum analyzer

April 5, 2017 / By Michael / In Ham Radio / 9 Comments

The HackRF One is a popular software defined radio (SDR) device, supporting not only reception but also the transmission of radio signals in the range between 1 MHz and 6 GHz. A new feature in the HackRF firmware now allows using it as a spectrum analyzer over the full 6 GHz range.

Fixing Roundcube’s command execution vulnerability in Debian Wheezy

December 7, 2016 / By Michael / In System Administration / Leave Comment

Recently a quite serious vulnerability (CVE-2016-9920) in Roundcube was reported. Until now (7th Dec) this vulnerability is unfixed in Debian’s roundcube packages (see the corresponding entry in the Debian Security Tracker).

The upstream patch is not directly applicable to version 0.7 which is used in Debian Wheezy but with a little modification it is. Following you find a corresponding patch*.
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IPv6 slowly gaining ground in Germany

February 25, 2016 / By Michael / In System Administration / Leave Comment

A few years ago I migrated some German websites to a new server and took the opportunity to make them accessible via IPv6. Later I wondered how many people actually access these websites over IPv6 and started collecting some data. Now, 15 months later, it’s time to have a look at it:

IPv6 usage for different German websites

Broken calendar migration from Google to ownCloud

October 2, 2015 / By Michael / In System Administration / Leave Comment

For some time now I run a small ownCloud instance to synchronize my contacts and calendars across different devices. When another person tried to migrate his Google calendars to this instance there was an issue though. The .ics files exported from Google contained invalid entries that were copied into ownCloud’s database and broke synchronization with 3rd party applications like Thunderbird’s Lightning extension.

Measuring time in a bare-metal Zynq application

July 1, 2015 / By Michael / In Reconfigurable Computing / 11 Comments

If you want to measure elapsed time in a bare-metal application on the Xilinx Zynq SoC—for example to measure how long your external accelerator takes to get a result—you will soon notice that typical methods do not work. But there is a simple and precise replacement for those methods.
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How systemd-timesyncd handles leap seconds

June 30, 2015 / By Michael / In System Administration / Leave Comment

This night we get another leap second, meaning that the last second of today is not 23:59:59 but 23:59:60 instead. The last time this happened was on June 30, 2012 and lead to issues on several servers due to bugs in the Linux kernel. Since then these bugs were fixed and also methods of hiding the leap second altogether were implemented. Here you can find a good overview over different configurations of kernel, ntpd and tzdata and how a leap second will be handled using these configurations. What is missing here is how a setup using systemd-timesyncd instead of ntpd will handle this situation.
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Zynq DDR self-refresh

May 27, 2015 / By Michael / In Reconfigurable Computing / Leave Comment

The Xilinx Zynq SoC supports disabling the DDR3 memory controller and the corresponding clocks to save energy. The memory can be put into self-refresh mode to retain its data. Inspired by a thread on the Xilinx forums I measured the actual effect of this power saving method on a Digilent ZedBoard.
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XST and the difficulty of proper addition

May 26, 2015 / By Michael / In Reconfigurable Computing / Leave Comment

More than a year ago I faced a strange issue with a hardware design on a Virtex-5 FPGA. Basically an addition of multiple values had no effect at all. Out of curiosity I reproduced this issue and now here are the details about what seems to be a serious bug in the XST synthesis tool for Virtex-5 FPGAs bundled with ISE 14.7.
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XPS on RHEL 7 / CentOS 7

May 24, 2015 / By Michael / In Reconfigurable Computing / Leave Comment

Officially the ISE suite is not supported to run on RHEL / CentOS 7. But since time moves on and Vivado nowadays is supported on those systems you may be tempted to run the ISE tools on this system as well.

If you face the issue that XPS just shows a blank window and even XPS project files are opened as text files, the following will probably solve this issue:

yum install mesa-libGLU

By now this was also mentioned on a Xilinx forum thread but I thought I’d post it anyway.