When I open the file with TextEdit (I don't want (truly, I am not able) to use vim), it is seen as "locked", even if I modify the permissions of the file via the "Get Info" window.
How can I modify the hosts file with TextEdit?
Open TextEdit as sudo
sudo -b /Applications/TextEdit.app/Contents/MacOS/TextEdit
Open /etc/hosts in this new TextEdit instance using any of the following methods:
Alternatively, you can edit in Terminal using nano:
SUDO_EDITOR=nano sudo -e /etc/hosts
sudo -e ensures that temporary files etc. are handled in the proper way and you don't run into permission issues with them.
nano is a simple console-based editor which is quite user-friendly.
You could try TextWrangler for this sort of thing; much more capable than TextEdit, and if you use the direct install from BareBones Software instead of the App Store version, it will happily open locked files. When you try, it asks permission, reminding you that you are not a member of the required group, but password entry will allow you to open and edit the file. Plus, it has optional command line additions (also not built in to App Store version) that will allow you to use TextWrangler by entering
edit (name of file) to open things directly from Terminal. Open File dialog has a handy "show invisibles" option to help you open and edit hidden or dot-prefixed files too. It's a free app so no risk in trying.