Ubuntu – Help with creating a symbolic link

symbolic-link

I'm confused with how symbolic links work. I hope someone can guide me in the right direction.

I want to put a demo online from our software, which normally only runs locally on a Mac Mini. So I put all the files in the var/www from my Ubuntu 12.04 server installation.

There are a lot of hardcoded links in the software which point to /Applications/XAMPP/xamppfiles/htdocs/narrowcasting

Of course, I could change all these code on my html/php files in /var/www, but that would be quite annoying. I hope I can fix this by creating a symbolic link. For example, I have a directory called thumb in /var/www/thumb. The PHP code is trying to put an image in /Applications/XAMPP/xamppfiles/htdocs/narrowcasting/thumb.

Can anyone give me a tip how to achieve this with a symbolic link?

Best Answer

use the ln command to do symbolic links.

 ln -s <real folder> <link folder>

in this example, you will create link folder that will actually contain what real folder have, and if you save something to link folder it will actually save it into real folder

You can verify the link with the command ls -l which will show an arrow to where the link points.

Note that the folder containing the link must exist, so you would have to create it first.

So in your situation, the commands that you are looking for are

sudo mkdir /Applications/XAMPP/xamppfiles/htdocs/narrowcasting

sudo ln -s /var/www/thumb /Applications/XAMPP/xamppfiles/htdocs/narrowcasting/thumb

Again, you can verify that the link was actually made with

ls -l /Applications/XAMPP/xamppfiles/htdocs/narrowcasting/thumb

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Symbolic-Link – Difference Between Symbolic Link and Hard Link After Unlink

I'll make a quick reference from an existing article,

With hardlink files,

When deleting files, the data part isn't disposed of until all the filename parts have been deleted. There's a count in the inode that indicates how many filenames point to this file, and that count is decremented by 1 each time one of those filenames is deleted. When the count makes it to zero, the inode and its associated data are deleted.

Please read The difference between hard and soft links for details.

Like, you may be interested in this other factoid on hardlinks,

the count also reflects how many times the file has been opened without being closed (in other words, how many references to the file are still active). This has some ramifications which aren't obvious at first: you can delete a file so that no "filename" part points to the inode, without releasing the space for the data part of the file, because the file is still open.

You could try that with your test-code.

btw: can you recheck your two cases?
I think you would get error for the symlink() case and success for the link() case.
I suggest you run them in different directories or use different file names for the two cases :-)

Ubuntu – Creating a symbolic link to a directory

Thanks everyone for your suggestions. I found it easiest to understand how to do it (though I still don't understand the logic behind it) with:

cd ~/workspace_b4a
cd android-sdk-linux
cd platform-tools
ln -sv ../build-tools/20.0.0/lib/ .

Best Answer

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Symbolic-Link – Difference Between Symbolic Link and Hard Link After Unlink

Ubuntu – Creating a symbolic link to a directory

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