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circular soft links

Posted on 2002-06-20
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Last Modified: 2013-12-26
I think I have softlinks that point to themselves somewhere on my system.  Is there a way to find and
diagnose circular links?
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Question by:cotec1
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13 Comments
 
LVL 21

Expert Comment

by:tfewster
ID: 7096939
ls -l `find . -type l -exec ls -l {} \; | awk '{print $NF}'` |grep "^l"
will list links to links [not very good practice, obviously!] - Hopefully that list will be short enough check manually.
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by:tfewster
ID: 7096998
In this scenario:
/tmp/junk> ls -lR
total 0
drwxr-xr-x   2 root       sys             96 Jun 20 19:20 d1
lrwxr-xr-x   1 root       sys              2 Jun 20 19:15 l1 -> l2
lrwxr-xr-x   1 root       sys              2 Jun 20 19:14 l2 -> l1

./d1:
total 0
lrwxr-xr-x   1 root       sys             12 Jun 20 19:20 l3 -> /tmp/junk/l1
lrwxr-xr-x   1 root       sys             12 Jun 20 19:17 ld1 -> /tmp/junk/d1

results in:
/tmp/junk> find . -follow -exec ls -ld {} \;
drwxr-xr-x   3 root       sys             96 Jun 20 19:16 .
drwxr-xr-x   2 root       sys             96 Jun 20 19:20 ./d1
find: ./d1/ld1 creates a cycle
lrwxr-xr-x   1 root       sys             12 Jun 20 19:17 ./d1/ld1 -> /tmp/junk/d1
find: cannot stat ./d1/l3
find: cannot stat ./l1
find: cannot stat ./l2

Of course, `find` may return the "cannot stat" error for other reasons, but it's a useful pointer to problems ;-)
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by:yuzh
ID: 7097708
Hi cotec1,

   You put this question on Soalris area as well, you should create a link for the question to save to points.

    I don't think you can make a  symbolic link to point to themselves.

Just ask yourseft a question, do you think the following command work ?
  ln -s test test
  The answer is NO !
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LVL 51

Expert Comment

by:ahoffmann
ID: 7098034
>  I don't think you can make a  symbolic link to point to themselves.
you can, unfortunately :-(
The answer is YES ! (at least for some flaviours of UNIX)
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Author Comment

by:cotec1
ID: 7098492
They don't actuall point back to themselves.  I should have been more specific in the description.  The links are causing our backups to go in to a loop, for instance:  There may be a link /home/cotec1/link_example > /home/cotec1

It points back to the directory that the link is in causing the backups to get trapped in a loop.

That is what I am trying to find.
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by:ahoffmann
ID: 7098661
to narrow down all possibilities: you're only interested in links pointing the a part of the physical part where it resides.
That would make a search easyer
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Expert Comment

by:tfewster
ID: 7098668
If you're using Solaris, my earlier suggestions won't work (I guess I can't persuade you to switch to HP-UX? ;-)

However, what are you using for backups? Even tar and cpio will copy links as links, rather than following the link (unless you specify the h option to tar)
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Author Comment

by:cotec1
ID: 7098690
We are using a no-frills, no-cost NT backup to a Mapped drive through Samba.  
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Expert Comment

by:ahoffmann
ID: 7098700
.. NT .. and which people adicted to NT, know about so sophisticated things like symbolic links? Just joking ...
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LVL 38

Expert Comment

by:yuzh
ID: 7098772
Why don't you just use Solaris to backup, a symbole link cost you no almost no tape space!
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Author Comment

by:cotec1
ID: 7098804
I have been working with our IT department to change our backup process.  The mode we are in now is temporary.  I think for a temp solution I am going to create a tar file for the backup and backup the tar file through NT/Samba.
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yuzh earned 300 total points
ID: 7098884
use: tar cvf dev-file-or-file file-list
will do the job for you.

    do not use:
    tar cvhf dev-file-or-file file-list
    -h it follow symbolic links and try to copy the normal
       file, you'll end up have mult-copies of the file in your tape.
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Expert Comment

by:bearware
ID: 7365476
If your backup interperates the likes as it does instead of just copying them as discussed above. Then when you restore a backup you WILL NOT get back to the original data symlinks will be lost, and you make need a biger disk drive.

Also symlinks to directorys closer to the root will probably be common and it will be futile to hunt them.
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