How to properly umount when the device is busy

Valic —  April 24, 2013 — 2 Comments

When you try to unmount a device sometimes you get this error: /media/sdxy: device is busy when you need to unmount a CD drive or to remove an external drive or anything else.The ideal situation is when your Linux is telling you what is keeping the device busy, but is not happening.

This is how to properly use umount command:

When you get this error,

# umount /media/sdxy
umount: /media/sdxy: device is busy
umount: /media/sdxy: device is busy

1. First thing you’ll probably do is to use fuser to find out what process is keeping your device busy. You can do it like this:

# fuser -m /dev/sdxy
/dev/sdxy: 230452
# ps -aux | grep 230452
root     230452  0.2  0.0  20756  3764 pts/0    Ss   22:35   0:00 -bash

You need to kill the 230452 process then umount the drive.

2. The second way to umount your drive is to use the -l argument from umount command. This is short for Continue Reading…

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How to avoid spelling mistakes with cdspell

Valic —  April 18, 2013 — Leave a comment

If you are not very good at typing or your keyboard is messing with you and you are making a lot of mistakes when you navigate on your Linux server this option will be very helpful to you:

Just add shopt -s cdspell in your .bashrc file and suddenly you will be very good at typing.

Some examples:

root@deb:cd /ect
/etc
root@deb:/etc#
root@deb:/var# cd miail
mail
root@deb:/var/mail#

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How to show hidden files in ProFTPd

Valic —  April 11, 2013 — Leave a comment

This is how you can enable hidden files(.htaccess) in ProFTPd.

Open proftpd.conf file and change ListOptions from -l to -a. Or if doesn’t exists add ListOptions -a to your proftpd.conf file.

nano /etc/proftpd/proftpd.conf

Change:

ListOptions "-l"

to:

ListOptions "-a"

Now restart proftpd and it’s done.

/etc/init.d/proftpd restart
Stopping ftp server: proftpd.
Starting ftp server: proftpd.

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How to use .htaccess to stop image hotlinking

Valic —  January 9, 2013 — Leave a comment

You can stop others from hotlinking your site images by placing a .htaccess  file in your website main directory:

RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)debian-tutorials.com/.*$ [NC]
RewriteRule \.(gif|jpg|png)$ http://www.debian-tutorials.com/wp-content/uploads/2012/12/hotlinkimage.png [R,L]

  1. The first line of the code enables the rewrite.
  2. The second line will block any website other than your own.
  3. The No case [NC] code will match the url regardless of being in upper or lower case letters.
  4. We allow empty referrals on the third line.
  5. The last line matches any files ending with the extension gif jpg and png. The hotlinked image will be replaced by the image specified here. You can also use here a link from another domain.
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How to fix [emerg]: could not build the server_names_hash, you should increase server_names_hash_bucket_size: 64

Valic —  January 5, 2013 — Leave a comment

This error usually appear when you test the nginx configuration.

If you want to fix this nginx error [emerg]: could not build the server_names_hash, you should increase server_names_hash_bucket_size: 64

Just add the following in your nginx.conf file:

http {
server_names_hash_max_size 512;
server_names_hash_bucket_size 128;

...
}

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