Before I forget, I would like to keep it here.

setfacl -Rm group:SOME_GROUP_NAME:r-x /foo

Sometimes, you may mess up with your grub and you can not even boot up your system because of the broken grub.

Here is a simple way to restore or re-setup grub.

1. Boot up your system with the first install CD or DVD to go to the rescue mode (e.g., linux rescue)
2. Let the rescue mode mount your linux partition(your root(/) partition) to /mnt/sysimage.
3. chroot /mnt/sysimage
4. grub-install /dev/hda ⇐ if your grub is not installed/messed up, try to reinstall it
5. grub
6. root (hd0,1) ⇐ The first number indicates the disk and second one is for the boot partition
7. setup (hd0)
8. quit
9. And get out of the rescue mode and then boot up your system without your installation CD / DVD

This is a very useful thing to remember when I need to run a remote X application on a local machine. Especially, when I need to test a web server which is not open to the public.
Before using ssh-tunneling, I had to setup ssh X-forward which is not safe at all and then run the web browser on the ssh-connected machine. This causes a really heavy traffic.

ssh -C -o CompressionLevel=9 -L 5901:localhost:5901 USER@hostname

Where

• USER needs to be replaced with your real username available on the server which you try to connect
• hostname is the hostname of your server. Of course, it can be just an IP address.
• 5901 can be any other ports to tunnel. 5901 is used for VNC

There is another good example to do ssh-tunneling for accessing the secondary remote host so that we don't have to do “ssh” twice (e.g., first ssh to the first remote host and then second ssh to the second remote host).

ssh oscar.osl.iu.edu -L 10000:192.168.0.101:22 -g

After setting up the ssh-tunneling like this, run the following command to access the second host directly.

ssh -p 10000 localhost

There are three things that you have to consider to make your remote X applications work on your Apple machine.

1. The server side configuration of SSH to allow “X11Forwarding=yes” on /etc/ssh/sshd_config (most linux boxes)
2. Turn on “X11” terminal application
3. Set the “DISPLAY” environment if it is not setup yet

         export DISPLAY=127.0.0.1:0.0
       or
         setenv DISPLAY 127.0.0.1:0.0
    

And then you can ssh into your remote machine and run any X applications.