SharePoint 2010/2013: Create custom My Site host template
This article demonstrates how to create a new My Sites host. Once you apply this My Site site host template, all new My Site will use this as a template to create a My Site.
Steps
Create a new My Site host.
Open Central admin > Application management > Create new site collection
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Provider Name, URL path, Select template as “My site host” and a site collection admin > Click OK
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Now you can make the required modification (e.g. custom master page, custom list, library, web part, etc.) in this My Site template.
Update this My Site Host site in User profile service application
Open Central admin > Application Management > Manage service application > User profile service application
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Under My site settings select “Setup My sites” > On my site host select the new My Site host we just created e.g. http://portal/sites/host > Click OK
Now all new my Site collections will use this as Host template
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Note
This My Site host does not affect any existing site. It only works on new My Sites.