So I have a question about binding directories to other directories.....

I have a folder where I keep my movies and music. My buddies want to be able to sftp in and rip my media. I made them a folder /bin/ftp where when they login they are bound to this directory and can only access their own directory inside /bin/ftp. But inside of /bin/ftp I want to make a "tunnel" to my media folder. I want this tunnel to be a read only tunnel so they can view my media and use the "get" commands but cant screw anything up....

Im trying to learn as much about ubuntu as possible so command line solutions would be appreciated, and please explain what each line does. I need to learn! haha

Hello,

You will want to create a symbolic link to your media directory using the "ln" command, using the -s argument. Look at the following:
Cheers,

Josh

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First thought - a subdirectory of /bin feels like a bad idea to me. /bin is for essential binaries ... in fact see Filesystem Hierarchy Standard:
Presumably each user has their own account and home directory on your system? You could just create a symlink, as corp679 suggests, within their home:
Or you could put a central ftp directory in /var

Second thought - by default the files in your home directory are readable but not writeable by another user. You can check the situation with ls -l and you can (probably should) set your other directories not to be readable by other users (with chmod).

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thanks for the input, I moved my /bin/ftp directory to just /ftp. That a better location?

Question about ln -s.....I did some googling and it looks like ln does not perform as well as other options. They compared it to mouth --bind. How would I do it using mount --bind? or is there an even better way?

Also, it looks like neither of these would survive a reboot. How do I make it survive a reboot?

afaik /ftp is fine.

Odd, I have not heard that a symlink would not perform as well - under what circumstances? Once the user has navigated to the right directory I would have thought it was identical. mount --bind should be an option but I haven't worked with it.

Creating a symlink creates a point on the file system and will definitely survive a reboot (imho). A mount would need to be rerun each time, via /etc/fstab (possibly) or an init script.

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Well I tried it out and everything worked great! Except for one thing....haha. Theres always a kicker.

I want to make the permissions 755, but symlinks are only 777. How can I get around this?

I think ... symlinks themselves don't need permissions, but the linked file/directory will control it.

Try creating or deleting a file in your media folder when logged in (or using su) as one of the sftp users. (Not the symlink itself, they will still be able to delete that).

Well normally I would be able to just change the permissions on the linked directory, but its on a partition and the data type of the partition does not allow permissions..... so the default is 777. So sadly that doesn't work...

Yup, that's correct. On a side note, create a hard link, and then look at the permissions...

Ah. Not good news. Now you might need to consider mount --bind.

Awesome. That works perfectly. Now that does not survive a reboot...so how would I make that happen?

I think someone else will need to advise on that! ...

haha alright. thanks so much of your help!