A method of booting an operating system in a container providing a file system virtualization environment isolated from a host computing environment hosting the container, the method comprising: receiving a specification of a composite device as a boot device, the composite device abstracting a first device as a primary layer of the composite device and a second device as a secondary layer of the composite device, wherein the first device and the second device of the composite device are accessed as the boot device in an hierarchical order such that the first device is accessed first, and the second device is accessed if information from the first device is unavailable; reading, in response to the receipt of the specification of the composite device as the boot device, operating system configuration data from a composite file system associated with the composite device , the composite file system abstracting, as a primary layer of the composite file system, a first file system providing access to data persisted on the first device and, as a secondary layer of the composite file system, a second file system providing access to data persisted on the second device; and utilizing the operating system configuration data to boot the operating system in the container , wherein the operating system configuration data is read from the first file system if the operating system configuration data is found in the first file system; and the operating system configuration data is read from the second file system based upon the operating system configuration data not being found in the first file system. receiving a specification of a composite device as a boot device, the composite device abstracting a first device as a primary layer of the composite device and a second device as a secondary layer of the composite device, wherein the first device and the second device of the composite device are accessed as the boot device in an hierarchical order such that the first device is accessed first, and the second device is accessed if information from the first device is unavailable; reading, in response to the receipt of the specification of the composite device as the boot device, operating system configuration data from a composite file system associated with the composite device , the composite file system abstracting, as a primary layer of the composite file system, a first file system providing access to data persisted on the first device and, as a secondary layer of the composite file system, a second file system providing access to data persisted on the second device; and utilizing the operating system configuration data to boot the operating system in the container , wherein the operating system configuration data is read from the first file system if the operating system configuration data is found in the first file system; and the operating system configuration data is read from the second file system based upon the operating system configuration data not being found in the first file system. the operating system configuration data is read from the first file system if the operating system configuration data is found in the first file system; and the operating system configuration data is read from the second file system based upon the operating system configuration data not being found in the first file system. <EOS>