Thread:Project:Support desk/mediawiki.log.js access denied when backing up (copying) mediawiki folder/reply (5)

No, this file just comes with MediaWiki and has nothing custom.

Yes, you can download your MediaWiki version again, extract that file out of the newly downloaded package and overwrite your old file with it. It will not change anything with any data in your wiki (which for the most part is stored in the database).

I dont't know, if what you describe can be caused by bad sectors; in that case I would expect that you can no longer read the file (e.g. when you open it in a text editor that does not work or you only see garbage).

I don't know what causes your problem. I once had the case that files were extracted in a folder and extracting them seemed to work (at least it did not give an error and the files were extracted). However, a few of the deepest files finally had a path and file name, which was longer then should be possible. Windows was unable to access the files. Through the tar tool, which I used to extract them I could finally remove them again... Maybe something like that is your problem?