FW: [patch 01/02] vfs: variant symlinks

FW: [patch 01/02] vfs: variant symlinks

[Schmidt, Kenneth P]

On 9/28/07 11:22 AM, "Jan Dittmer" <jdi@l4x.org> wrote:

> Ken Schmidt wrote:
>> Variant symlinks add the ability to embed variables in to the
>> contents of symbolic links so their targets can change based on
>> outside sources (user environment, uts, filesystems, etc.)
> 
> Could you elaborate why this is needed and what part cannot
> be solved in userspace (linkfarm on tmpfs or intelligent
> scripts)?

Several networked filesystems (i.e. afs) have similar concepts.  This just
moves it into the vfs layer so that it can be used on all of them and even
local filesystems.

The best example of how this can be useful is to allow a heterogeneous
environment which uses a common filesystem. For example, both x86_64 and
power systems could mount a root nfs share and execute with a common set of
configurations and data, but the binary directories (bin and lib) could
point to architecture specific directories.

Re: FW: [patch 01/02] vfs: variant symlinks

[Al Viro]

On Sat, Sep 29, 2007 at 12:40:23PM -0700, Schmidt, Kenneth P wrote:

> The best example of how this can be useful is to allow a heterogeneous
> environment which uses a common filesystem. For example, both x86_64 and
> power systems could mount a root nfs share and execute with a common set of
> configurations and data, but the binary directories (bin and lib) could
> point to architecture specific directories.

mount --bind /usr/$(ARCH)/bin /usr/bin
mount --bind /usr/$(ARCH)/lib /usr/lib

or corresponding ones in /etc/fstab.  BFD...

Re: FW: [patch 01/02] vfs: variant symlinks

[Trond Myklebust]

On Sat, 2007-09-29 at 12:40 -0700, Schmidt, Kenneth P wrote:

> The best example of how this can be useful is to allow a heterogeneous
> environment which uses a common filesystem. For example, both x86_64 and
> power systems could mount a root nfs share and execute with a common set of
> configurations and data, but the binary directories (bin and lib) could
> point to architecture specific directories.

That would hardly be a portable NFS environment. Boot a Solaris, or
older Linux kernel, and watch your applications barf...

This sort of stuff belongs in the automounter, not the kernel.

Trond