Re: improvement for 'ln' to add the '-m' switch

[Dragan Simic]

Hello,

On 2024-02-09 09:22, aotto wrote:
> I understand your concern because from a technical point of view a
> "link" and "mount" is something total different
> *but* from an end-user point of view the end-user want to have the
> "srcDir" mapped (I use "mapped" because I want *not*
> use the term "link" or "mount") into the "tgtDir" because the end-user
> *require* this.

As Bernhard already explained, linking files and performing mounting
are two distinctively separate, different operations.  As such, they
belong to two different userspace utilities.

> for my special case the "ln -s .." is even don't work with git and so
> I was left scan the internet for such a simple task.
>
> the classic "mount" feature does even *not* fit because, as you
> mentioned also, the mount does *not* survive a reboot.

Perhaps you can add the required mount commands to the startup
scripts of your system.  Even more conveniently, bind mounts can be
defined in /etc/fstab, [1] please read the fstab(5) man page.

> I came up with the "ln -m ..." purpose because this is the end-user
> front-end for "mapping" a directory/file into an other place.
> I understand that this is *not* easy because to survive a reboot
> without "spam" the "/etc/fstab" definitely require a new technology.

As already explained, such an approach simply wouldn't fit into
the way things are intended to work, despite what they might look
like when viewed from the end-user perspective.

[1] https://man.archlinux.org/man/fstab.5


> On 09.02.24 09:10, Bernhard Voelker wrote:
> > [+coreutils ML]
> >
> > On 2/8/24 17:43, aotto wrote:
> > > Hi, I write to you because of a suggestion from the "https://serverfault.com/"; 
> > Q&A side
> >
> > you sent this to my personal email, so you're lucky this didn't land 
> > in spam.
> > Hence I'm hereby forwarding to the coreutils mailing list.
> >
> > > subtract: add a "-m" switch to "ln" to support "mount -bind srcDir tgtDir"
> > >
> > > As reference please read:
> > >
> > > → 
> > https://serverfault.com/questions/1153146/improvement-add-new-switch-to-ln-called-m-to-link-a-directory-as-mount
> > >
> > > As original reference please read:
> > >
> > > → 
> > https://stackoverflow.com/questions/77954023/git-check-in-a-file-in-a-symlink-directory-fails/77960139#77960139
> > >
> > >
> > > mfg
> > >
> > >    aotto
> >
> > ln(1) is the userland tool for the link/linkat system calls for hard 
> > links
> > and for the symlink/synlinkat system calls for symbolic aka soft 
> > links.
> > Both hard and soft links are persisted in the file system.
> >
> > mount(1)-ing is a completely different matter, because it tells the 
> > kernel
> > to well, mount(2), one file system (or part of it) on another place, 
> > and
> > this is gone when the system reboots.
> >
> > Therefore, I don't see any common point in this, and therefore adding 
> > such
> > a functionality to ln(1) is the wrong thing to do.