Jtdylktuy

I'm trying to better understand symbolic links... and not having very much luck. This is my actual shell output with username/host changed:

username@host:~$ mkdir actual

username@host:~$ mkdir proper

username@host:~$ touch actual/file-1.txt

username@host:~$ echo "file 1" > actual/file-1.txt

username@host:~$ touch actual/file-2.txt

username@host:~$ echo "file 2" > actual/file-2.txt

username@host:~$ ln -s actual/file-1.txt actual/file-2.txt proper

username@host:~$ # Now, try to use the files through their links

username@host:~$ cat proper/file-1.txt

cat: proper/file-1.txt: No such file or directory

username@host:~$ cat proper/file-2.txt

cat: proper/file-2.txt: No such file or directory

username@host:~$ # Check that actual files do in fact exist

username@host:~$ cat actual/file-1.txt

file 1

username@host:~$ cat actual/file-2.txt

file 2

username@host:~$ # Remove the links and go home :(

username@host:~$ rm proper/file-1.txt

username@host:~$ rm proper/file-2.txt

I thought that a symbolic link was supposed to operate transparently, in the sense that you could operate on the file that it points to as if you were accessing the file directly (except of course in the case of rm where of course the link is simply removed).

Symlinks tend to like full paths or relative to the link, otherwise they can often be looking for file-1.txt locally (oddly enough).

Navigate to proper and execute ls -l and you can see that the symlink is looking for actual/file-1.txt, when it should be ../actual/file-1.txt.

So you have two options:

1. 
   

   Give the full path

   
   
   

   ln -s ~/actual/file-1.txt ~/actual/file-2.txt ~/proper
   
   

   
   


2. 
   

   Navigate to the folder you want the link to be in and link from there

   
   
   

   cd proper
   
   ln -s ../actual/file-1.txt ../actual/file-2.txt ./
   
   

   
   

Edit: A hint to save typing.

You could just do ln -s ~/actual/file-{1,2}.txt ~/proper

The items in the curly braces are substituted and placed after each other, creating the command

ln -s ~/actual/file-1.txt ~/actual/file-2.txt ~/proper

which links both files to the target directory. Saves some major typing as you get further on in the shell.

The problem is the usage of relative paths. If you specify your link creation with the full explicit path, it works.

$ ln -s ~/actual/file1.txt ~/actual/file2.txt ~/proper/

$ cat proper/file1.txt

file 1

$

Your example creates links in proper that look for a subdirectory named actual under the current directory, rather than your intended parent-of-both.

Symbolic links can be tricky.  In essence, a symbolic link is a file that contains a filename/pathname for another file (and that is flagged for special treatment).  If the pathname in the link file begins with ‘/’, then it is treated as an absolute pathname, and things are fairly straightforward.  If it doesn’t begin with a slash, it is treated as a relative pathname — relative to the directory where the link is located.  (This is true whether or not the name contains slashes.)  So, you created proper/file–1.txt as a link to “actual/file–1.txt”, and when you tried to access it, the system tried to access proper/actual/file–1.txt.  You should have said

ln –s  ../actual/file–1.txt  ../actual/file–2.txt  proper

By the way, you didn’t need the touch commands.  echo "file 1" > actual/file–1.txt is sufficient to create actual/file–1.txt.

A related issue, and it may be obvious to many, but stumped me for a few minutes: if you're creating a symlink within a directory that is itself symlinked, or there's a symlink within the path of the current working directory, you might run in to problems with symlinks not working.

Use cd .. and ls -l repeatedly, to see if your parent directories are themselves symlinked.

If you need to create a symlink, cd to the original Target directory, and create new symlinks there, so the relative paths are accurate.

Or to put it another way: the relative path is from the Origin to the Target. If the Origin is subsequently symlinked, that's OK. But you might run in to problems setting up a new Origin link_name within a directory that is itself somehow symlinked.

When you try to create a link to a file that doesn't exist (or you've given the path incorrectly) ln -s doesn't throw an error. It creates a link but when you try 'cat' on that link it says no file found. Even when you can see it using ls. In such cases always double-check your file path.

ubuntu@ip-172-31-80-155:~/lab5$ ln -s etc/ufw/ufw.conf link1

ubuntu@ip-172-31-80-155:~/lab5$ ls -al

total 5360

drwxrwxr-x 2 ubuntu ubuntu    4096 Mar  9 18:56 .

drwxr-xr-x 7 ubuntu ubuntu    4096 Mar  9 18:42 ..

-rwxr--r-- 1 ubuntu ubuntu 5478400 Mar  9 18:32 backup.tar

lrwxrwxrwx 1 ubuntu ubuntu      16 Mar  9 18:56 link1 -> etc/ufw/ufw.conf

ubuntu@ip-172-31-80-155:~/lab5$ cat link1

cat: link1: No such file or directory

Because the file etc/ufw/ufw.conf doesn't exist. The correct path is /etc/ufw/ufw.conf

ubuntu@ip-172-31-80-155:~/lab5$ ln -s /etc/ufw/ufw.conf link2

ubuntu@ip-172-31-80-155:~/lab5$ ls -l

total 5352

-rwxr--r-- 1 ubuntu ubuntu 5478400 Mar  9 18:32 backup.tar

lrwxrwxrwx 1 ubuntu ubuntu      16 Mar  9 18:56 link1 -> etc/ufw/ufw.conf

lrwxrwxrwx 1 ubuntu ubuntu      17 Mar  9 19:00 link2 -> /etc/ufw/ufw.conf

ubuntu@ip-172-31-80-155:~/lab5$ cat link2

# /etc/ufw/ufw.conf

#



# Set to yes to start on boot. If setting this remotely, be sure to add a rule

# to allow your remote connection before starting ufw. Eg: 'ufw allow 22/tcp'

ENABLED=no



# Please use the 'ufw' command to set the loglevel. Eg: 'ufw logging medium'.

# See 'man ufw' for details.

LOGLEVEL=low