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diff --git a/www/posts/linux/2021-06-05/xrandr-failed-to-get-size-of-gamma-for-output-default/index.html b/www/posts/linux/2021-06-05/xrandr-failed-to-get-size-of-gamma-for-output-default/index.html index 3720159..006b031 100644 --- a/www/posts/linux/2021-06-05/xrandr-failed-to-get-size-of-gamma-for-output-default/index.html +++ b/www/posts/linux/2021-06-05/xrandr-failed-to-get-size-of-gamma-for-output-default/index.html @@ -20,7 +20,7 @@ <body> <section><h1>Xrandr: Failed to Get Size of Gamma for Output Default</h1><blockquote>Sat 5th June 2021 By David T. Sadler.</blockquote><p>After updating a laptop to Ubuntu 20.04 I found that the resolution of the display was fixed at 1024x1028 with no option in the settings for changing it to correct resolution of 1368x768.</p><p>Now normally I would fall back on using the xrandr command to add the missing resolution.</p><p>First the output of cvt command gives me the VESA CVT mode lines for the resolution and refresh rate.</p><pre><code class="shell">$ cvt 1366 768 60 -Modeline "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync</code></pre><p>This mode is then added with xrandr.</p><pre><code class="shell">$ xrandr --newmode "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync</code></pre><p>The mode can then be associated with the display.</p><pre><code class="shell">$ xrandr --addmode default 1368x768_60</code></pre><p>Like I said, normally this is all that is required but in this instance the xrandr command kept displaying the below message and the desired resolution would not be applied.</p><pre><code class="shell">xrandr: Failed to get size of gamma for output default</code></pre><p>After several fruitless attempts at fixing this I eventually found that the nomodeset kernel boot option had been set. This instructs the kernel to not load any video drivers and instead use BIOS modes. Apparently many open source drivers have removed support for non-kernel modes and fall back to using a very basic VESA driver. I'm assuming this basic driver does not support the resolution I want.</p><p>With further investigation I found that nomodeset was been specified via grub so removing it meant re-configuring grub by editing /etc/default/grub.</p><pre><code class="shell">$ sudo vim /etc/default/grub</code></pre><p>In this file I located the below line.</p><pre>GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"</pre><p>I edited this line to remove nomodeset and saved the changes.</p><pre>GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"</pre><p>Now all I needed to do was update grub with the new default settings.</p><pre><code class="shell">$ sudo update-grub</code></pre><p>After a reboot the laptop was using the correct resolution and there was no need to use xrandr.</p><h3>Links</h3><a href="https://askubuntu.com/questions/207175/what-does-nomodeset-do">askubuntu/ question regarding nomodeset does.</a><a href="/posts/linux/">Linux - Read More Posts.</a><p>I don't have comments as I don't want to manage them. You can however contact me at the below address if you want to.</p><a href="mailto:david@davidtsadler.com">Email david@davidtsadler.com</a><h3>License</h3><a href="https://creativecommons.org/licenses/by-sa/4.0/">The contents of this site is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.</a><p>Copyright © 2021 David T. Sadler.</p><a href="/">Return to Homepage.</a></section> +Modeline "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync</code></pre><p>This mode is then added with xrandr.</p><pre><code class="shell">$ xrandr --newmode "1368x768_60.00" 85.25 1368 1440 1576 1784 768 771 781 798 -hsync +vsync</code></pre><p>The mode can then be associated with the display.</p><pre><code class="shell">$ xrandr --addmode default 1368x768_60</code></pre><p>Like I said, normally this is all that is required but in this instance the xrandr command kept displaying the below message and the desired resolution would not be applied.</p><pre><code class="shell">xrandr: Failed to get size of gamma for output default</code></pre><p>After several fruitless attempts at fixing this I eventually found that the nomodeset kernel boot option had been set. This instructs the kernel to not load any video drivers and instead use BIOS modes. Apparently many open source drivers have removed support for non-kernel modes and fall back to using a very basic VESA driver. I'm assuming this basic driver does not support the resolution I want.</p><p>With further investigation I found that nomodeset was been specified via grub so removing it meant re-configuring grub by editing /etc/default/grub.</p><pre><code class="shell">$ sudo vim /etc/default/grub</code></pre><p>In this file I located the below line.</p><pre>GRUB_CMDLINE_LINUX_DEFAULT="quiet splash nomodeset"</pre><p>I edited this line to remove nomodeset and saved the changes.</p><pre>GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"</pre><p>Now all I needed to do was update grub with the new default settings.</p><pre><code class="shell">$ sudo update-grub</code></pre><p>After a reboot the laptop was using the correct resolution and there was no need to use xrandr.</p><h3>Links</h3><a href="https://askubuntu.com/questions/207175/what-does-nomodeset-do">askubuntu/ question regarding nomodeset does.</a><a href="/posts/linux/">Linux - Read More Posts.</a><p>I don't have comments as I don't want to manage them. You can however contact me at the below address if you want to.</p><a href="mailto:david@davidtsadler.com">Email david@davidtsadler.com</a><h3>License</h3><a href="https://creativecommons.org/licenses/by-sa/4.0/">The contents of this site is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.</a><p>Copyright © 2021 David T. Sadler.</p><a href="/">Return to Homepage.</a></section> <script defer src="/js/highlight.min.js"></script> <script defer src="/js/site.js"></script> </body> |