&quot;FreeBSD jails is the same concept as Docker, even it has been around for longer. Can somebody explain why it has never gained more momentum?&quot;<p>The very first VPS provider[1] based their offering on jail and FreeBSD.  They still offer them today (I sold the business in 2004).<p>We didn&#x27;t call them &quot;VPS&quot; - that term came about later, in 2002 I think ... we called them &quot;server instances&quot;.<p>We also didn&#x27;t have any of these nifty deployment&#x2F;monitoring&#x2F;management tools - there was nothing but jail(8).<p>[1] JohnCompanies in 2001.