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  • Debugging native file system watcher for Linux

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Due to tons of variations of Linux environment recently introduced native file system watcher for Linux may refuse to function properly. Here are some simple steps which may help to track down a problem.


Make sure you are using the latest versions (download them from Git repository), they are named fsnotifier and fsnotifier64, placed into bin/ directory of IDEA, and granted execution rights.


Execute watcher in self-diagnostics mode:

Code Block
$ ./fsnotifier --selftest

It should print something like this:

Code Block
fsnotifier[5661]  info: started (self-test mode)
fsnotifier[5661] debug: inotify fd: 4
fsnotifier[5661]  info: inotify watch descriptors: 524288
fsnotifier[5661]  info: updating roots (curr:0, new:1)
fsnotifier[5661]  info: registering root: /home/sher/Tools/idea-IU-dev/bin
fsnotifier[5661] debug: watching /home/sher/Tools/idea-IU-dev/bin: 1
fsnotifier[5661]  info: unregistering root: /home/sher/Tools/idea-IU-dev/bin
fsnotifier[5661] debug: unwatching /home/sher/Tools/idea-IU-dev/bin: 1 (0x9795068)
fsnotifier[5661]  info: finished

Examine its output for any errors or warnings.

Warning: fsnotifier will try to setup a watch for directory tree starting from current directory – if hierarchy is deep, there will be lots of output.

Activate logging

The next step is to activate logging for watcher and see what's happening in real.

Watcher utilizes "user" facility of syslog(3) – messages usually can be found in /var/log/user.log. Verbosity is regulated via FSNOTIFIER_LOG_LEVEL environment variable, possible values are: debug, info, warning, error, off.

By default logging is switched off. To activate it set FSNOTIFIER_LOG_LEVEL to appropriate value before starting IDEA, e.g.:

Code Block

Warning: "debug" verbosity level may produce really huge amount of messages – use with care.

If you see something suspicious in logs please feel free to post it here as comment (or via attachment if your log is long enough).