xreader: pdf thumbnails do not work

[MikeNavy]

Hi, When I install Firejail, PDF thumbnailing is disabled; old PDF thumbnails stay there, but when a new PDF document is created / copied, there is no thumbnail created, iust a PDF icon.

System: Linux Mint Mate 20.3 Una (based on Ubuntu 20.04 LTS Fossa, with Mate 1.26 desktop environment). File Manager: caja Thumbnailer: xplayer-thumbnailer "Thumbnailer for xreader". Firejail: Installed version "firejail_0.9.68-apparmor_1_amd64.deb" from https://sourceforge.net/projects/firejail/files/firejail/firejail_0.9.68-apparmor_1_amd64.deb/download

The problem occurs as soon as Firejail deb is installed, even without desktop integration (no use of "$ sudo firecfg").

To reproduce the problem:

• install Firejail,
• open file manager,
• copy / paste an existing PDF file,
• the copied file has no thumbnail, just a PDF icon.

To correct the problem:

• uninstall Firejail,
• open file manager,
• copy / paste an existing PDF file,
• the copied filed has a thumbnail.

It seems that Firejail prevents xplayer-thumbnailer to function.

[MikeNavy]

Not sure if PDF thumbnails are made by xreader or by xplayer-thumbnailer; xplayer-thumbnailer is presented as "Thumbnailer for xreader", but it might be a typo instead of "Thumbnailer for xplayer". Checked: PDF thumbnails are generated by "xreader-thumbnailer", part of xreader package.

[rusty-snake]

The problem occurs as soon as Firejail deb is installed, even without desktop integration (no use of "$ sudo firecfg").

Can you watch sudo firemon so wee which sandboxes are running/started when you test this.

[MikeNavy]

Hi,

• I completely uninstalled Firejail.
• Then installed it again.
• I launched no sandbox, no "sudo firecfg".
• "sudo firemon" gives no answer, empty screen.
• Once again I copy / paste a PDF file, the copied file has a PDF icon, not a thumbnail.
• "sudo firemon" output still empty.

[MikeNavy]

Hi, I have finally found the root cause and solved the problem.

It seems that, in a former attempt to use Firejail, it had created symbolic links from "/usr/bin" to "/usr/local/bin". In the links created, I could find "xreader", "xreader-thumbnailer" (xreader is the default document reader, including PDF format, for Linux Mint). The links created did not point to the original executable but to firejail: as an example, the "/usr/local/bin/xreader-thumbnailer" pointed to "/usr/bin/firejail". I suppose that links had been created when using a "sudo firecfg"... When Firejail is uninstalled, these symbolic links are not removed and point to non-existing firejail command, without consequence. But as soon as Firejail is installed again, the symbolic links point to firejail command, and xreader-thumbnailer does not work any longer.

I found a workaround:

• install symlinks, "sudo apt install symlinks"
• open a terminal in "/usr/local/bin",
• list dangling links with "symlinks .",
• delete dangling links with "sudo symlinks -dr .". (there were some 35 dangling links pointing to firejail)

Now, when I install Firejail (0.9.72-1), without firecfg, pdf thumbnailing still works and I can use Firejail to launch some appimages (it works well with LibreOffice or BlueGriffon appimages, not with Squishpic one).

This creation of symbolic links pointing to firejail should be documented (is it a consequence of firecfg?), and a way to recover original links or to delete links should exist. Note that, with the links and Firejail installed, xreader-thumbnailer does not work, there is a confirmed bug.

Regards,

MN

[rusty-snake]

This creation of symbolic links pointing to firejail should be documented (is it a consequence of firecfg?), and a way to recover original links or to delete links should exist.

Both are documented.

xreader-thumbnailer does not work, there is a confirmed bug.

Does it not work at all or only when called by mate?

[rusty-snake]

If I have to guess xreader-thumbnailer.profile misses a noblacklist ${HOME}/.path/to/thumbnails.

[kmk3]

@MikeNavy on May 1:

This creation of symbolic links pointing to firejail should be documented (is it a consequence of firecfg?)

Yes, they are created by firecfg; see man firecfg.

and a way to recover original links or to delete links should exist.

Run sudo firecfg --clean.

[MikeNavy]

Hi, @rusty-snake Normally, pdf thumbnails are automatically created when I open a directory where pdf files are found, using Mate file manager, Caja. When the symlinks are there and Firejail installed, thumbnails creation does not work. When the symlinks are there and Firejail not installed, thumbnails creation does work. When the symlinks are not there (removed) and Firejail installed, thumbnails creation does work. Yes, something is probably wrong in xreader-thumbnailer profile. Path to thumbnails is "~/.cache/thumbnails" on my computer (Linux Mint 20.3, based on Ubuntu 20.04).

@kmk3 I had thought that uninstalling Firejail deb and its configuration files would have been enough, I understand now that, if the symlinks have been ceated after installation, they cannot be removed such a way. I have tested "sudo firecfg" followed by "sudo firecfg --clean", symlinks are created with the 1st command and removed with the 2nd one.

Regards,

MN