Mailinglist Archive: opensuse (3566 mails)
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Re: [opensuse] Another back-up question - Over & over again
- From: Randall R Schulz <rschulz@xxxxxxxxx>
- Date: Mon, 30 Apr 2007 11:27:49 -0700
- Message-id: <200704301127.49488.rschulz@xxxxxxxxx>
On Monday 30 April 2007 11:13, Carlos E. R. wrote:
> The Monday 2007-04-30 at 16:55 +0200, jdd wrote:
> > I never really understood was arise, but I think I had cross links
> > (links from a partitio to an other and vice-versa)
>
> It is safe to copy "the link" but not the file that the link is
> pointing to. On the other hand, when doing a backup, you might find
> out that the backup is full of links which are not saved elsewhere...
> so one has got to be careful.
It's important to distinguish hard links from symbolic links.
Hard links are fundamentally restricted from ever crossing file system /
device / volume boundaries. This is because all the hard links to a
file are co-equal. It's not that one is "the file" and others
are "links." This kind of link is the reference from a directory entry
to an inode and takes the form of a simple integer index in the inode
table. Because it has this form, in which the device / file system
volume is implicit and must be equal to the one on which the directory
entry resides. Manually created hard links cannot refer to directories.
The only hard links to directories are those created automatically when
directories are created or moved (specifically, the link from the
parent to the directory, the "." entry in the directory and the ".."
entries in all immediate sub-directories).
Symbolic links _are_ asymmetric. A symbolic link is quite distinct from
the entity to which it refers (which may by any kind of file system
entity, including directories). A symbolic link is just a plain file
that contains a substitute file name (relative or absolute) to use when
the symlink is accessed. Symbolic links may cross file system
boundaries because there referents (the thing to which they point) have
no implicit component or aspect other than the directory in which the
symlink resides in the case that the symlink's value is a relative path
name.
> --
> Cheers,
> Carlos E. R.
Randall Schulz
--
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For additional commands, e-mail: opensuse+help@xxxxxxxxxxxx
> The Monday 2007-04-30 at 16:55 +0200, jdd wrote:
> > I never really understood was arise, but I think I had cross links
> > (links from a partitio to an other and vice-versa)
>
> It is safe to copy "the link" but not the file that the link is
> pointing to. On the other hand, when doing a backup, you might find
> out that the backup is full of links which are not saved elsewhere...
> so one has got to be careful.
It's important to distinguish hard links from symbolic links.
Hard links are fundamentally restricted from ever crossing file system /
device / volume boundaries. This is because all the hard links to a
file are co-equal. It's not that one is "the file" and others
are "links." This kind of link is the reference from a directory entry
to an inode and takes the form of a simple integer index in the inode
table. Because it has this form, in which the device / file system
volume is implicit and must be equal to the one on which the directory
entry resides. Manually created hard links cannot refer to directories.
The only hard links to directories are those created automatically when
directories are created or moved (specifically, the link from the
parent to the directory, the "." entry in the directory and the ".."
entries in all immediate sub-directories).
Symbolic links _are_ asymmetric. A symbolic link is quite distinct from
the entity to which it refers (which may by any kind of file system
entity, including directories). A symbolic link is just a plain file
that contains a substitute file name (relative or absolute) to use when
the symlink is accessed. Symbolic links may cross file system
boundaries because there referents (the thing to which they point) have
no implicit component or aspect other than the directory in which the
symlink resides in the case that the symlink's value is a relative path
name.
> --
> Cheers,
> Carlos E. R.
Randall Schulz
--
To unsubscribe, e-mail: opensuse+unsubscribe@xxxxxxxxxxxx
For additional commands, e-mail: opensuse+help@xxxxxxxxxxxx
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