A computer implemented method, comprising: mounting, at a seamless file system, SFS, extension to an operating system running within a computer system, a remote file system of a server; receiving, at the SFS extension, a read request from an application program executing on the computer system, wherein the read request includes a request to access, for read access only, a portion of a file stored at the mounted remote file system of the server; in a network access application program running within the computer system: receiving, from the SFS extension, the read request; transforming the read request into a network communications request conforming to a communications protocol, wherein the communications protocol is compatible with the server; forwarding the network communications request to the server; receiving the requested portion of the file from the server, the requested portion of the file being a read-only portion smaller than a complete file; and caching, locally within the computer system, the requested portion of the file received from the server; and in the SFS extension, using the requested portion of the file to respond to the read request as an ordinary file system response, wherein the requested portion of the cached file is hidden, by the file system of the operating system, from a second application program running within the computer system other than the first application program. mounting, at a seamless file system, SFS, extension to an operating system running within a computer system, a remote file system of a server; receiving, at the SFS extension, a read request from an application program executing on the computer system, wherein the read request includes a request to access, for read access only, a portion of a file stored at the mounted remote file system of the server; in a network access application program running within the computer system: receiving, from the SFS extension, the read request; transforming the read request into a network communications request conforming to a communications protocol, wherein the communications protocol is compatible with the server; forwarding the network communications request to the server; receiving the requested portion of the file from the server, the requested portion of the file being a read-only portion smaller than a complete file; and caching, locally within the computer system, the requested portion of the file received from the server; and receiving, from the SFS extension, the read request; transforming the read request into a network communications request conforming to a communications protocol, wherein the communications protocol is compatible with the server; forwarding the network communications request to the server; receiving the requested portion of the file from the server, the requested portion of the file being a read-only portion smaller than a complete file; and caching, locally within the computer system, the requested portion of the file received from the server; and in the SFS extension, using the requested portion of the file to respond to the read request as an ordinary file system response, wherein the requested portion of the cached file is hidden, by the file system of the operating system, from a second application program running within the computer system other than the first application program.