I have a ton of files, 50,000+, in my thumbnails subdirectory ($HOME/.thumbnails). I was wondering what these are thumbnails of? I expect most of them come from the file manager (Thunar in my case), gthumb, etc.

I ask, because there are a few sensitive things I have stored as images on my computer. Things like marriage licenses, social security cards, select pages from tax returns, etc. These sensitive documents are stored encrypted (truecrypt), but I was wondering if this .thumbnail directory and its gigantic amount of contents is a possible security leak. For example, I may use truecrypt to mount an encrypted container, but then I use the file manager, gthumb, and other applications to view these things. Are all these applications creating thumbnails? Thumbnails aren't going to contain as much resolution as the original images, but in some cases they could contain enough to represent a problem, especially the "large" thumbnails.

So, how do you manage this .thumbnail stuff? Can you just delete the entire .thumbnail subdirectory if you have concerns about security? I assume it will be automatically recreated and repopulated. Thumbnails would be handy in some situations, but a potential security liability in others, if indeed they are created willy-nilly as I am assuming.

they are just thumbnail images of images

so if you do not want anyone seeing small versions of photos or videos ........
delete them or use "shred" on them

I use a cronjob to remove older than three days.

It does pose a security risk and so I have located and turned off thumbnailing functionality of the file manager and image viewer. Technically, I wrote my own image viewer, because many write temporary files to disk even if they aren't thumbnails. However, viewnior works well and doesn't write files to disk.

You could see what happens if you make ~/.thumbnails a symbolic link to /dev/null I've not tried it myself. Or you could make ~/.thumbnails a symbolic link to a directory in somewhere that gets wiped on boot. /tmp/ may mounted as tmpfs or on disk depending on your distro and if the latter, it may or may not be wiped on boot depending on your distro. If it's not wiped on boot you could make it be. /dev/shm/ is in RAM so certainly will be cleared on boot. Note that you'd have to put something in place to ensure that the target directory gets recreated after boot, you could do that in ~/.bash_profile or somewhere like that.


Note that the Thumbnail Managing Standard now conforms to XDG Base Directory Specification so on at least some current distros thumbnails are stored in ${XDG_CACHE_HOME}/thumbnails/ If $XDG_CACHE_HOME isn't set thumbnails are in ~/.cache/thumbnails/