[Bug 1892949] Re: [SRU] grub can no longer detect kernels after ubuntustudio-lowlatency-settings is uninstalled

[Erich Eickmeyer]

** Description changed:

- ubuntustudio-lowlatency-settings does not contain a postrm script to
- reenable executability (+x bit) of /etc/grub.d/10_linux after it has
- been removed, thus rendering grub unable to detect any installed
- kernels, potentialy breaking installations.
+ [Impact]
+ 
+  * When ubuntustudio-lowlatency-settings is installed, it disables the executable 
+    bit on /etc/grub.d/10_linux because it installs a replacement file at 
+    /etc/grub.d/09_lowlatency in order to ensure that the lowlatency kernel is 
+    always default when both generic and lowlatency are installed.
+ 
+  * ubuntustudio-lowlatency-settings does not contain a postrm script to reenable 
+    executability (+x) of /etc/grub.d/10_linux after it has been removed, thus 
+    rendering grub unable to detect any installed kernels, potentialy breaking 
+    installations and causing people's systems unable to boot.
+ 
+ [Test Case]
+ 
+  * Install Ubuntu Studio or add ubuntustudio-lowlatency-settings to any 
+    installation
+ 
+  * Uninstall ubuntustudio-lowalatency-settings, run update-grub.
+ 
+  * Reboot. Kernels will be unavailable for boot. This is further proven prior to 
+    this when update-grub is run as it will not detect any installed kernels.
+ 
+ [Regression Potential]
+ 
+  * The only regression this may have is that the .postrm script does not actually 
+    add +x, but this is highly unlikely as it adds it if the /etc/grub.d/10_linux 
+    file simply exists, even if the executable bit is already set.
+ 
+ [Other Information]
+ 
+  * This was recently discovered when I installed the surface-linux kernel on my 
+    MS Surface Pro 4 and found it unable to boot the custom kernel, as with 
+    ubuntustudio-lowlatency-settings it was only recognizing the generic and 
+    lowlatency kernels. Removing ubuntustudio-lowlatency-settings and attempting
+    to run update-grub resulted in no kernels detected. Upon investigation,
+    I discovered that the +x bit was not set in /etc/grub.d/10_linux.

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https://bugs.launchpad.net/bugs/1892949

Title:
  [SRU] grub can no longer detect kernels after ubuntustudio-lowlatency-
  settings is uninstalled

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