Bug #86742 refman-5.7-en.pdf instructs to $chown -R mysql . #from /usr directory
Submitted: 19 Jun 2017 5:08 Modified: 26 Oct 2017 16:08
Reporter: Brian Wells Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S2 (Serious)
Version:5.7.18 OS:Ubuntu (16.04 LTS)
Assigned to: CPU Architecture:Any
Tags: basedir, chown

File: Maximum allowed size is 50MB.
Description:
Privacy:

If the data you need to attach is more than 50MB, you should create a compressed archive of the data, split it to 50MB chunks, and upload each of them as a separate attachment.

To split a large file: