On 08/31/2015 10:25 PM, William Harrington wrote:
On Mon, August 31, 2015 18:47, Simon Kitching wrote:
Hi All,
Some examples in the LFS book create symbolic links as follows:
ln -sfv ../../lib/$(readlink /usr/lib/libz.so) /usr/lib/libz.so
while some create them like this:
ln -sv /proc/self/mounts /etc/mtab
ln -sv /tools/lib/libgcc_s.so{,.1} /usr/lib
As far as I can see, all links under /usr/lib which point back to stuff
under /lib use relative paths, while links pointing to config-files and
temporary hacks use absolute.
Is there any reason why relative is preferred over absolute in some
cases? I do find the absolute paths easier to understand..
It really depends on what you want to do.
The classic case for relative links is for a project directory tree so
that when the project is backed-up, moved, or duplicated to another place
in which case absolute links would be confusing and dangerous.
Absolute links are good for something such as systemwide tools where
multiple versions are installed, such as different versions of the GNU
Compiler Collection.
In a nutshell, if the files are in the same relative positions and may be
moved around, relative links are good. If the file is in a known location,
such as a config file, then absolute links would be good.
Sorry, should have been more explicit. I was wondering about the use of
rel vs abs symlinks *in this particular LFS context* (/usr/lib->/lib). I
couldn't see any reason why "/usr/lib" would get moved, so saw no
difference between relative ("/usr/lib/../../lib/foo") and absolute
("/lib/foo") usage in this case except that absolute is slightly more
readable.
Initially, the LFS root is mounted in the host system as "/mnt/lfs", so
the relative links would point to the right files there, while absolute
links would not. But I can't see that making any difference, as
presumably nobody _expects_ those links to be usable in that circumstance.
I certainly agree with you (and Bruce) that relative links have their
purposes - just wasn't sure if there was something special reason to use
relative here (eg to do with chroots or something). Looks like it is
just a stylistic choice, which is fine. And as Bruce noted in another
email, demonstrating both relative and absolute symlinks is good for the
reader.
Thanks, Simon
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