20
File tagging software?
(hexbear.net)
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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
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For images, you can use a photo library application like digikam and set tags on the files, which are saved both to a relational database and to the photo metadata inside the image file. For other file types I don't think there's anything standard.