Code Freeze is a free wordpress plugin to change your wordpress site temporarily into read only state.
Main features:
Disables adding/editing/deleting new content, media, themes, etc.
Disables installing/activating/deactivating/updating/deleting all plugins
Disables new comments/trackbacks on all content items
Removes the QuickPress widget and notices to upgrade core or plugins
Provides notice to dashboard users that any changes will be lost
Provides generally “read only” access to the dashboard
Login to wordpress (wp-admin).
In your admin dashboard click plugins and select Add New.
Type Code Freeze in the search field and click Search Plugins button.
Install Code Freeze.
After the successfully Installation click the activate Plugin link to activate the plugin.
[OR]
Download Code Freeze wordpress plugin. Download link
Unzip and upload it to your WordPress wp-content/plugins directory.
Login to wp-admin. In your admin dashboard click plugins and activate the Code Freeze wordpress plugin