From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dave Schwartz Subject: Re: Mirror a file system on the fly Date: Fri, 19 Aug 2005 11:27:49 -0400 Message-ID: <3e32b777050819082723b0f8d6@mail.gmail.com> References: <3e32b777050818124045dcd1f0@mail.gmail.com> <1124395116.5222.396.camel@localhost> <3e32b77705081813273f887aef@mail.gmail.com> <1124398992.5222.404.camel@localhost> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Cc: linux-fsdevel@vger.kernel.org Return-path: Received: from wproxy.gmail.com ([64.233.184.199]:30809 "EHLO wproxy.gmail.com") by vger.kernel.org with ESMTP id S1751147AbVHSP17 convert rfc822-to-8bit (ORCPT ); Fri, 19 Aug 2005 11:27:59 -0400 Received: by wproxy.gmail.com with SMTP id i20so588184wra for ; Fri, 19 Aug 2005 08:27:50 -0700 (PDT) To: Ram Pai In-Reply-To: <1124398992.5222.404.camel@localhost> Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Ram, Your code snippet seems to work great as discussed. Thanks. :-) However, my requirement is slightly different. What I also want is that any file created from the mirrored/cloned file-system must not be available in the parent file system. Gracias, decebel On 8/18/05, Ram Pai wrote: > On Thu, 2005-08-18 at 13:27, Dave Schwartz wrote: > > Hi Ram, > > Thanks for the inputs. I was going over the man pages describing the > > clone system call and its option of CLONE_NEWNS. Could understand the > > description only in parts. > > > > The man page suggests that this flag when set, the cloned child is > > started in a new name space, initialized with a copy of the parent. > > Now does that mean, a program like a shell when cloned with > > CLONE_NEWNS set, will have a copy of file hierarchy of the underlying > > parent process? > > Yes the child process will see an exact copy of all the mounts of > various filesystems as that of the parent. However if you mount/unmount > any filesystems in the child, the same will not be mounted/unmounted in > the parent and vice-versa. Each has its individual view of the > the filesystem heirarchy. > > Try the following program that clones off a child process with a mirror > namespace and gives you a bash prompt. Try mounting and unmounting > in this bash prompt and see if the same is visible in a totally > different window. > > > #include > #include > #include > > char somemem[4096]; > > int myfunc(){ > system("bash"); > } > > int > main(int argc, char *argv[]) > { > if(clone(myfunc, somemem, CLONE_NEWNS|SIGCHLD, NULL)) { > wait(NULL); > } else { > printf("clone failed\n"); > } > printf("exit\n"); > } > > > Hope this helps, > RP > > > > > > > > Gracias, > > decebel > > > > > > > > On 8/19/05, Ram Pai wrote: > > > On Thu, 2005-08-18 at 12:40, Dave Schwartz wrote: > > > > Hi list, > > > > > > > > Not too sure if this is the right forum to ask this question but since > > > > my requirement is around linux filesystems, I shall take this liberty > > > > to post my question. > > > > > > > > My requirement is to develop a kernel/user space module to add an > > > > extension to the shell program environment such that this shell forks > > > > a mirror look-alike filesystem of the underlying OS to the programs > > > > run in that particular shell. > > > > > > u seem to be talking about namespaces, if I get you right. > > > > > > there is a flag CLONE_NEWNS to the system call 'clone' which does what > > > u r talking about. > > > > > > RP > > > > > > > > > > > > > > > > > > > > > > > > Was trying to look thru the FAQ and a few list archives to look for > > > > ideas around my requirement. The archives were overwhelming. > > > > > > > > > > > > Any ideas/pointers will be a great help, > > > > Gracias, > > > > decebel > > > > - > > > > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > > > > the body of a message to majordomo@vger.kernel.org > > > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > >