As gzip command only compresses a file not a directory, you should use another tool like tar. I hope it is available on your web server
Please find out where is tar by running the command:
$ whereis tar
You should see if your web server is running Ubuntu like mime
tar: /bin/tar /usr/include/tar.h /usr/share/man/man1/tar.1.gz
In your config.php, you can set
$cfg->pathtozip = '/bin/tar';
$cfg->ziprecursearg = '-zcf';
You can now export your porfolio into a zip file. Please then change the file extension from .zip to .tar.gz.
This is a workaround for your issue of lacking zip command.
Cheers,
Son Nguyen
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