Re: Mirror a file system on the fly
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 <[EMAIL PROTECTED]> 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 [EMAIL PROTECTED]
> > > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
> >
> -
> To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
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Re: Mirror a file system on the fly
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? Gracias, decebel On 8/19/05, Ram Pai <[EMAIL PROTECTED]> 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 [EMAIL PROTECTED] > > 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 [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Mirror a file system on the fly
On Fri, 2005-08-19 at 01:10 +0530, 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. > > > 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, The chroot command and mount --bind should give you a good start. > Gracias, > decebel -- David Kleikamp IBM Linux Technology Center - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: Mirror a file system on the fly
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 [EMAIL PROTECTED] > 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 [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
