I upgraded my server to a newer version of Linux in December. Today I suddenly noticed that I see "No image generated" yellow banner across all images in the TYPO3 backend.

Normal steps in such cases would be to go and check ImageMagick installation using the TYPO3 Install tool:

There is a special section there for image tests:

Basic tests for reading graphics formats told me that convert did not produce any results.

I know what it means. I run Apache in the chrooted environment and after upgrades copies of ImageMagick in the chroot jail are not the same as outside of it. So I upgraded binaries in the jail but it did not change anything. Hmmmm.

I went to chroot jail and tried to call convert from there. Here is what I got:

convert: UnableToOpenConfigureFile `delegates.xml' @ configure.c/GetConfigureOptions/553.

delegates.xml is a file that contains ImageMagick configuration for image conversions with external programs. So it must be missing. I checked /usr/share/ImageMagic-x.y.z and that directory was empty.

"This is easy" I thought. I reinstalled ImageMagick and ran convert again. Huh? Same error? Checking the directory: it is still empty.

Finally I managed to solve it. I had to delete ImageMagick completely with all its dependencies and install it fresh. Than it worked. Now I have my thumbnails again!