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Dirk Mittler's Blog

A Journal of my Ongoing Experiences.

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  • Apache
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  • Custom-Compile
  • DCT
  • Debian
  • Debian 9
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  • Downtime
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  • GPU
  • HBS-750
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  • Kernel Update
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  • memcached
  • MOSFET
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  • MySQL
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  • Power Failure
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  • Successful Update
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  • Update
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  • WordPress
  • X-Server

Most Directly-Viewed, Individual Posts

  • One reason Why, It is Difficult For Me to Guess, at the Variable-Length Encoding of numbers, Chosen By Other People (7,605)
  • Testing the Focusrite Scarlett 2i2 external sound device, with my Samsung S6 Smart-Phone (5,285)
  • My Experiences with the Bell Home Hub 3000 (5,255)
  • I can offer a sound-compression scheme that I know will not work, as a point of reference. (4,881)
  • How DynDNS Works (2,801)
  • I now have Linux installed on my Samsung Galaxy Tab S. (2,425)
  • Getting Pulseaudio to schedule real-time threads under Debian / Stretch and beyond. (2,261)
(Hit Counters Installed March 5, 2016)

Recent Posts:

  • Guessing at the discretization, of the Sallen-Key Filter, with Q-Multiplier.
  • Installing Chrome on Old Debian Versions (Redirect from Installing Old Chrome Version on Debian).
  • How the chain rule applies to integral equations.
  • Exploring the Discrete Sine Transform…
  • Power Failure Today, Downtime
  • Samsung’s Auto Hot-Spot Feature
  • How to route a USB MIDI Keyboard to a JACK-MIDI Input, under Debian.

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  • How the chain rule applies to integral equations. | Dirk Mittler's Blog on There has been some confusion about the Sinc-Filter.
  • Exploring the Discrete Sine Transform… | Dirk Mittler's Blog on How the chain rule applies to integral equations.

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Tag: System Processes

Casual Maintenance today – No Worries

I apply the unusual procedure, of hosting this Web-site and blog, on a personal computer at home, which I name ‘Pheonix’ on my LAN, and not on a professional hosting-service. What this results in is a personal computer, which has an unusually large amount of RAM dedicated to non-user processes, such as for instance the Apache Web server, the MySQL server, and various other services that assist in hosting the actual site, while also assigning much RAM to my user-space processes, that create a full KDE desktop-session.

It would be an oversimplification to say, that the system-services actually run as root, because many of them switch from root to a different user-name, that just exists for one Web-service to run, but which is not root, simply to protect my computer against eventual hacking-attempts. For example, if my Web-server was to run entirely as root, and if a hacker was able to find a PHP-scripting vulnerability, he could get the thread in question to vandalize my whole computer. But in reality, the Apache thread he’d be hijacking runs with limited privileges…

One of the facts about this setup that is not ideal, is that the user-space processes that create my desktop-session, from my perspective in the foreground, actually take up more RAM than my Web-services do, just because I have such an extensive KDE setup, with PIM-services etc.. What actually happens is that as this user-session continues to run, there is a miscellanea of memory-leaks within, due to which more and more virtual addresses are allocated. Fortunately, because this is also a 64-bit system, the risk is very small, that it could actually ‘run out of 64-bit numbers’ to assign. But what this does also mean, is that an increasing amount of data – most of that presumably garbage – gets swapped out into my swap-partition over time.

This can make me feel uncomfortable, because when and if the next power-failure hits, I could lose data, simply because data which was not garbage, could be swapped-out at that moment. So when this type of imbalance has reached a certain point, what I tend to do is a log-out / log-in. This maneuver does not really reboot the computer, unmount my file-systems, or restart the kernel. It just tells my extensive desktop-session to save all its data to permanent files and databases, to exit, and then to restart. My system-processes continue to run, unaffected. Therefore, the visibility of my site, and of this blog, are not affected at all, when I do this, as long as the procedure went smoothly.

This afternoon, I enacted this procedure, and it went smoothly.

Continue reading Casual Maintenance today – No Worries

Posted on October 1, 2017Tags Apache, Log-In, Log-Out, Memory Leaks, MySQL, Plex Server, Routine Maintenance, Swap File, System Processes, X-Server1 Comment

Successful X-server Update Today

Today the Debian / Jessie package maintainers pushed through an update to my X-server, bringing that up to version ‘2:1.16.4-1+deb8u1‘. In a case like this, it’s better to restart the session, just to load the new X-server version, but also, to make sure that any problems in running the X-server do not take us by surprise, during some later reboot.

As it happens, the computer this took place on, which I name ‘Phoenix‘, is also my Web-server. And so it’s desirable to perform the restart of the session, without doing a full reboot of the computer. Under Linux, with the ‘KDE’ desktop manager, we can do this by just Logging Out, and then Logging back In. Doing so also causes an X-server restart.

Not doing a full reboot of my computer, also meant that my Apache Web-server continued running, without causing any disruption to the visibility of my Web-site, or of this blog.

Yet, there was a glitch. As I told my user-session to log out, the display hanged, with the mouse-pointer still visible, but with the rest of my display black, and with no further activity on the hard-drive. In this situation I can help myself, by using the KDE, <Ctrl>+<Alt>+Backspace key-combination, to force an X-server restart. Doing so successfully ended my user-session. Then, the X-server restarted, and I got to log back in.

What this means is that the preparatory work I did according to this earlier posting, has paid off.

I count this as a successful update.

Dirk

 

Posted on July 9, 2017July 9, 2017Tags Apache, KDE, Log-In, Log-Out, System Processes, System Services, Update, User Processes, User Space, Web-server, X-ServerLeave a comment on Successful X-server Update Today

KDE Update This Morning

This morning, effectively as I slept, my Linux computer named ‘Phoenix’ downloaded and installed a set of updates, to KDE, which is the framework installed on this computer, for managing the display of my Desktop / GUI, as well as for PIM. Because this update installed itself unattended, it meant that user-processes were still running, which did not have the latest version of the software loaded into RAM.

This can happen easily on Linux computer-systems, which generally just keep working that way – in the short term. But in the long term, eventually something is going to want to wake up a KDE-program which is not already running, and which will want to use the latest images, at which point some sort of incompatibility could set in.

Fortunately though, KDE will only affect user-processes, as I just wrote, but will not affect system-processes, such as my Apache Web-server, or the instance of the MySQL-server, which is running as a system- rather than as a user-process. And so what I can do in this case, is just log out the user, and log him back in. Doing so also reloads the X-server, which does a shutdown as well, and restarts the graphics-driver.

Both the update to KDE, as well as my log-out, log-in maneuver, worked well, without any hint at first glance, of anything going wrong. As a  result, the availability of the site and my blog were unaffected. Also, the ‘memcached‘ process is a system-process that did not require any restart, so that the responsiveness of my blog, to the most-frequent requests for postings from readers, should still be as quick as it was only 30 minutes ago.

Dirk

 

Posted on May 12, 2017Tags Apache, KDE Update, KDE-PIM, Log-In, Log-Out, memcached, MySQL, Routine Update, Successful Update, System Processes, User Processes, Web-serverLeave a comment on KDE Update This Morning
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