is it correct to change all magento folders permission to 755 and all files to 644 using chmod?

Question

is it correct if i change all files permisson to 644 and all folders to 755 using following commands?

find . -type f -print0 | xargs -0 chmod 0644
find . -type d -print0 | xargs -0 chmod 0755

Answer 1

No. For one thing, mage should be executable. Also, your database password is in app/etc/local.xml, so you want to make that not readable by world. You don't really need find to accomplish setting the permissions. From the mage root:

chmod -R -x . # remove execution bit from everything
chmod o-r app/etc/local.xml
chmod +x mage
chmod -R ug+rwX . # make files read/write, dirs rwx for owner and group

This doesn't reset the permissions for other users other than for app/etc/local.xml.

Answer 2

Yes, those commands are technically correct in terms of using chmod to affect those changes.

The permissions you listed are fine if the server you are on is running PHP / the webserver as your FTP user, and all files and directories are owned by you. This would be the case with php-fpm, or PHP as a CGI and using suphp.

If however, your host is running PHP as mod_php, and Apache is set to a generic "nobody" or "www" user, then a few directories (recursively) need to be world writable (chmod 0777):

var/
downloader/
media/