topic Re: symlinks -r -d / in Operating System - Linux

symlinks -r -d /

'chris' — Tue, 20 May 2008 16:30:59 GMT

hi

what happens after this command:

# symlinks -r -d /

on linux ?

Re: symlinks -r -d /

Steven Schweda — Tue, 20 May 2008 16:49:03 GMT

"man symlinks"?

-d causes dangling links to be removed.

-r recursively operate on subdirectories within the same filesys-
tem.

"on linux" is not a very useful description
of the system.

Re: symlinks -r -d /

'chris' — Tue, 20 May 2008 17:00:59 GMT

thanks, but what dangling links means ?

Re: symlinks -r -d /

Steven Schweda — Tue, 20 May 2008 17:14:39 GMT

> [...] but what dangling links means ?

I guess that it means that you didn't take
the "man symlinks" hint offered earlier.

"man symlinks":

dangling links are those for which the target of the link does not cur-
rently exist. This commonly occurs for absolute links when a filesys-
tem is mounted at other than its customary mount point (such as when
the normal root filesystem is mounted at /mnt after booting from alter-
native media).

For information on most commands, "man
command" is often helpful. In this case,
"man symlinks".

Did you try "man symlinks"?

"man symlinks" might help.

Re: symlinks -r -d /

James R. Ferguson — Tue, 20 May 2008 19:16:25 GMT

Hi Chris:

A simple way to find dangling symbolic links is to use this Perl snippet:

# perl -MCwd=realpath -MFile::Find -wle 'find(sub{print $File::Find::name," -> ",realpath($_) if -l && ! -e},@ARGV)' /path

Pass the /path argument that represents the directory that you want to examine. If there are dangling links, this reports them. For example, do:

# touch /tmp/myfile
# ln -s /tmp/myfile /tmp/mylink
# rm /tmp/myfile
# perl ...
/tmp/mylink -> /tmp/myfile

...which exposes '/tmp/mylink' as a dangling symbolic link.

Regards!

...JRF...

Re: symlinks -r -d /

Dennis Handly — Sun, 25 May 2008 04:50:17 GMT

On HP-UX anyway, if you use "ls -lL" on a directory, any dangling link would have bogus permissions, owner, group and time. Then you could just grep for that pattern.

Re: symlinks -r -d /

'chris' — Sun, 25 May 2008 09:27:54 GMT

thanks to ALL,

do I understand correct ?

symlinks -r -d /

cannot damage my linux system ?

Re: symlinks -r -d /

Steven Schweda — Sun, 25 May 2008 17:28:14 GMT

> [...] cannot damage my linux system ?

It _probably_ won't. I can _imagine_ someone
using a dangling link for data storage, like
a simple text file, so I wouldn't _guarantee_
that it's safe.

ln -s 'Any text may be stored here.' fred
symlinks .
dangling: /house/antinode/fred -> Any text may be stored here.

Have you looked at the output without "-d",
to see what will happen with "-d"?

If you have any doubts about the safety of
"symlinks -d", why do you want to do it?

Re: symlinks -r -d /

Dennis Handly — Tue, 27 May 2008 02:22:14 GMT

>Steven: I can _imagine_ someone using a dangling link for data storage, so I wouldn't _guarantee_ that it's safe.

That's exactly what netscape does to prevent multiple instances. It has a .lock that is linked to the value of DISPLAY and maybe the PID.

Re: symlinks -r -d /

James R. Ferguson — Tue, 27 May 2008 12:28:06 GMT

Hi (again) Chris:

> symlinks -r -d / ...cannot damage my linux system ?

If it is a *personal* system, then it's up to you to choose. If this is a company/production server, then I'd be a bit more careful.

Instead of capraciously removing all dangling links, I would do:

# symlinks -r / | grep dangling

...and exaxmine the output. Then, perhaps on a case-by-case basis make a determination to manually remove ('rm') dangling links that you don't want.

A dangling link isn't necessarily a "bad thing". For instance, you might want to keep symbolic links to an installation CD/DVD/USB. I might have:

# symlinks -r /home
dangling: /home/jrf/install -> /media/JRF_DISK/ARCHIVE.tar

...which I might wish to retain for times when I actuall mount a USB device named "JRF_DISK".

Regards!

...JRF...