Here’s one way, using the bash shell and a few handy linux utilities.

1. The bash $RANDOM function. It generates a random number between 0 – 32767.
2. Linux DD utility, to output files.
3. /dev/(h|s)da, your hard drive in linux.
4. All wrapped in a bash while loop.

So lets start. First define a bash variable with the number of files we wish to create, lets say 10.

no_of_files=10

Then we’ll assign the a bash variable for the counter.

counter=1

As for the dd command, this creates a file with random content from your hard disk. (Mine’s /dev/sda) which is 1KB in size. The count switch tells dd to repeat 1024 bytes 1 time, thus the 1Kb file size. skip makes dd skip an x amount of bytes before reading further. Since this requires raw access to your hard drive, you’ll have to run this as root unfortunately.

dd bs=1024 count=1 skip=0 if=/dev/sda of=random-file

So now imagine, if we let bash assign the count and skip random numbers, we get random file contents. (Light bulbs flashing eh?)

Of course, all of it will be written to a single file called random-file in my case. To add just slight amount of variety, we can add the counter variable that we will use in our while loop as an extension. The dd command will now be:-

 dd bs=1024 count=$($RANDOM) skip=$($RANDOM) if=/dev/sda of=random-file.$counter

Finally, we will wrap it up in a bash while loop like this:-

no_of_files=10;
counter=1;
while [[ $counter -le $no_of_files ]];
 do echo Creating file no $counter;
  dd bs=1024 count=$RANDOM skip=$RANDOM if=/dev/sda of=random-file.$counter;
  let "counter += 1";
 done

When you run it, you will get output like this:-

Creating file no 1
16614+0 records in
16614+0 records out
17012736 bytes (17 MB) copied, 0.29308 s, 58.0 MB/s
Creating file no 2
14456+0 records in
14456+0 records out
14802944 bytes (15 MB) copied, 0.100101 s, 148 MB/s
.................
Creating file no 10
25224+0 records in
25224+0 records out
25829376 bytes (26 MB) copied, 0.492113 s, 52.5 MB/s

when you do a directory listing, you’ll see this:-

[root@atreides rd-test]# ls -lh
total 226M
-rw-r--r-- 1 root root 17M 2009-07-29 00:25 random-file.1
-rw-r--r-- 1 root root 25M 2009-07-29 00:25 random-file.10
-rw-r--r-- 1 root root 15M 2009-07-29 00:25 random-file.2
-rw-r--r-- 1 root root 20M 2009-07-29 00:25 random-file.3
-rw-r--r-- 1 root root 21M 2009-07-29 00:25 random-file.4
-rw-r--r-- 1 root root 30M 2009-07-29 00:25 random-file.5
-rw-r--r-- 1 root root 22M 2009-07-29 00:25 random-file.6
-rw-r--r-- 1 root root 27M 2009-07-29 00:25 random-file.7
-rw-r--r-- 1 root root 25M 2009-07-29 00:25 random-file.8
-rw-r--r-- 1 root root 29M 2009-07-29 00:25 random-file.9

For more info, refer to the $RANDOM function from the Advanced Bash Scripting Guide.

First make sure you install the Adobe yum repository.

As root:-

rpm -ivh http://linuxdownload.adobe.com/adobe-release/adobe-release-i386-1.0-1.noarch.rpm

Then install the flash plugin.

yum install flash-plugin.i386

The flash plugin will be installed in /usr/lib/flash-plugin/libflashplayer.so

Chrome plugins are supposed to be located in /usr/lib/chromium-browser/plugins. So lets create a symbolic link, so that whenever your Adobe flash plugin is updated, your Chrome automatically gets the latest version.

n -sv /usr/lib/mozilla/plugins/libflashplayer.so /usr/lib/chromium-browser/plugins/libflashplayer.so

Now start your Chrome browser from the command line, with the --enable-plugins switch. This will enable the flash plugin.

Here’s a screenshot of me watching a video from youtube on chrome:-

Flash Player in Google Chrome for Linux

Say goodbye to geek productivity once this is done

1. Install bind and bind-chroot packages

   # yum install bind bind-chroot

2. Edit your /etc/sysconfig/named file.

   # vim /etc/sysconfig/named

   Add the following line:

   ROOTDIR="/var/named/chroot"

3. Edit your /etc/named.conf file.

   # vim /etc/named.conf

4. Change the following line:

   listen-on port 53 { 127.0.0.1; };

   to

   listen-on port 53 { any; };

   This allows the bind daemon to listen on all your network IPs, not just your loopback(127.0.0.1) address.

5. Change this line:

   allow-query     { localhost; };

   to

   allow-query     { 192.168.0.0/24; };

   You now allow all the machines in your home LAN to use your DNS server.

6. Make sure it starts at boot time.

   # chkconfig named on

   Restart your DNS server.

   # service named restart

7. Make sure its listening on the correct ports.

   # netstat -ntupl | grep named

   In my case, the DNS server IP is 192.168.0.10. So, as seen here, the line udp 0 0 192.168.0.10:53 0.0.0.0:* 2851/named shows it is listening correctly.

8. Then test your server from another machine in your network. Most probably another linux box or laptop.

   # dig @192.168.0.10 google.com

   The dig command, with the ‘@’ instructs it to get the IP address for google.com from your newly set up server. On my machine, it looked like this:-

   [root@atreides ~]# dig @192.168.0.10 google.com
    
   ; < <>> DiG 9.6.1-RedHat-9.6.1-2.fc11 < <>> @192.168.0.10 google.com
   ; (1 server found)
   ;; global options: +cmd
   ;; Got answer:
   ;; ->>HEADER< <- opcode: QUERY, status: NOERROR, id: 6515
   ;; flags: qr rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 4, ADDITIONAL: 0
    
   ;; QUESTION SECTION:
   ;google.com.			IN	A
    
   ;; ANSWER SECTION:
   google.com.		300	IN	A	74.125.127.100
   google.com.		300	IN	A	74.125.45.100
   google.com.		300	IN	A	74.125.67.100
    
   ;; AUTHORITY SECTION:
   google.com.		171853	IN	NS	ns3.google.com.
   google.com.		171853	IN	NS	ns1.google.com.
   google.com.		171853	IN	NS	ns2.google.com.
   google.com.		171853	IN	NS	ns4.google.com.
    
   ;; Query time: 82 msec
   ;; SERVER: 192.168.0.10#53(192.168.0.10)
   ;; WHEN: Sat Jul 18 20:14:59 2009
   ;; MSG SIZE  rcvd: 148

   Note the SERVER: line. that shows you the answer for the query came from my DNS server (192.168.0.10).

9. Finally, set up your /etc/resolv.conf accordingly.

   On the server:

   nameserver 127.0.0.1

   And on all your other machines:

   nameserver 192.168.0.10

Unlike Windows, which requires some registry editing or even specialized tools, its just a command line away in Linux.

For example, lets change the MAC address of your first netwrok card, usually called eth0.

Let’s swith to being the root user and view the current MAC address:-

ifconfig eth0

You should get something similiar:-

[root@rhel-5new ~]# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 08:00:27:2C:D2:B5
          inet addr:192.168.0.108  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe2c:d2b5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:20545 errors:0 dropped:0 overruns:0 frame:0
          TX packets:18348 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:10083277 (9.6 MiB)  TX bytes:7489363 (7.1 MiB)
          Interrupt:11 Base address:0xd020

The MAC address is listed next to the HWAddr column, which is 08:00:27:2C:D2:B5 in this case.

We’ll change it. First shutdown the network interface.

ifconfig eth0 down

Now change it to say, 08:00:27:2C:D2:B4.

ifconfig eth0 hw ether 00:00:27:2c:d2:b4

Bring the interface back up.

ifconfig eth0 up

Finally, lets have a look at the new mac address.

[root@rhel-5new ~]# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:00:27:2C:D2:B4
          inet addr:192.168.0.108  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::200:27ff:fe2c:d2b4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:20957 errors:0 dropped:0 overruns:0 frame:0
          TX packets:18642 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:10146055 (9.6 MiB)  TX bytes:7520724 (7.1 MiB)
          Interrupt:11 Base address:0xd020

You can see that the HWaddr field now reports 00:00:27:2C:D2:B4.

First, make sure you have aspell installed. In Fedora, just yum install it.

$ yum install aspell

You’ll also need a dictionary, from which aspell can search for words.
A yum search aspell will give you a list.

[raja@atreides visilon]$ yum search aspell
-----------------------------------------------------------
aspell-af.i586 : Afrikaans dictionaries for Aspell
aspell-bg.i586 : Bulgarian dictionaries for Aspell
aspell-br.i586 : Breton dictionaries for Aspell
aspell-ca.i586 : Catalan dictionaries for Aspell
aspell-cs.i586 : Czech dictionaries for Aspell
aspell-cy.i586 : Welsh dictionaries for Aspell
aspell-da.i586 : Danish dictionaries for Aspell
aspell-de.i586 : German dictionaries for Aspell
aspell-el.i586 : Greek dictionaries for Aspell
aspell-en.i586 : English dictionaries for Aspell
aspell-es.i586 : Spanish dictionaries for Aspell
aspell-fr.i586 : French dictionaries for Aspell
aspell-ga.i586 : Irish dictionaries for Aspell
aspell-gl.i586 : Galician dictionaries for Aspell
aspell-hr.i586 : Croatian dictionaries for Aspell
aspell-id.i586 : Indonesian dictionaries for Aspell
aspell-is.i586 : Icelandic dictionaries for Aspell
aspell-it.i586 : Italian dictionaries for Aspell
aspell-no.i586 : Norwegian dictionaries for Aspell
aspell-pl.i586 : Polish dictionaries for Aspell
aspell-pt.i586 : Portuguese dictionaries for Aspell
aspell-ru.i586 : Russian dictionaries for Aspell
aspell-sl.i586 : Slovenian dictionaries for Aspell
aspell-sr.i586 : Serbian dictionaries for Aspell
aspell-sv.i586 : Swedish dictionaries for Aspell
aspell-fo.i586 : Faeroese dictionaries for Aspell
aspell-gd.i586 : Gaelic dictionaries for Aspell
aspell-nl.i586 : Dutch dictionaries for Aspell
aspell-ar.i586 : Arabic dictionary for Aspell
aspell-bn.i586 : GNU Aspell Bengali Dictionary Package
aspell-gu.i586 : GNU Aspell Gujarati Dictionary Package
aspell-he.i586 : Hebrew dictionary for Aspell
aspell-hi.i586 : GNU Aspell Hindi Dictionary Package
aspell-ml.i586 : GNU Aspell Malayalam Dictionary Package
aspell-mr.i586 : GNU Aspell Marathi Dictionary Package
aspell-or.i586 : GNU Aspell Oriya Dictionary Package
aspell-pa.i586 : GNU Aspell Punjabi Dictionary Package
aspell-sk.i586 : Slovak dictionaries for Aspell
aspell-ta.i586 : GNU Aspell Tamil Dictionary Package
aspell-te.i586 : GNU Aspell Telugu Dictionary Package

That’s a lot of languages. I’ll just install the English dictionaries.

yum install aspell-en.i586

Now the fun part. Checking your spelling via command line.
Just type aspell -a and it will give you a prompt. I’ll intentionally type a misspelled word and see what it returns:-

[raja@atreides visilon]$ aspell -a
@(#) International Ispell Version 3.1.20 (but really Aspell 0.60.6)
psychatrist
& psychatrist 5 0: psychiatrist, psychiatrists, psychiatrist's, psychiatry's, psychiatric

I spelt ‘psychiatrist’ wrongly, and it gave me back a few suggested corrections. (Ok I admit, I didn’t know how to spell it in the first place. )

Lets see what happens when you give it a correctly spelled word:-

[raja@atreides visilon]$ aspell -a
@(#) International Ispell Version 3.1.20 (but really Aspell 0.60.6)
disapprove
*

Yes, it returns an asterisk(*), showing you’re spelling is correct.
Press Ctrl + D when you’re done, to bring you back to the command line.

If you have a text file, you could check that using aspell as well. For example, here’s some sample text:-

Mary had a little lamb. It's fleede was whote as snow.

We’ll save it as mary.txt and run aspell like this to check the file:

aspell check mary.txt

You’ll get a interface like this, highlighting every misspelled word, with the suggested actions.

Aspell in action

When done with the checking, aspell will exit, saving the previous copy with a .bak extension.

First, the task we are going to do:

We have a list of files:

[raja@atreides test]$ ls
data_file_1   data_file_2  data_file_4  data_file_6  data_file_8
data_file_10  data_file_3  data_file_5  data_file_7  data_file_9

We have been instructed to replace the underscores (_) in the file names with hyphens (-).

A menial task not really suited for humans. We’ll start building a script for this, one piece at a time.

1. Check which type of shell you are using.

   echo $SHELL

   As I am using bash scripting, make sure the result is /bin/bash

2. List out all the file that you wish to rename

   $ ls data_file_*

   It should give you output like this:-

   [raja@atreides test]$ ls data_file_*
   data_file_1   data_file_2  data_file_4  data_file_6  data_file_8
   data_file_10  data_file_3  data_file_5  data_file_7  data_file_9

3. Lets display each one of this in a for loop.

   for file_name in `ls data_file_*`; do echo "The file:" $file_name; done

   What this for loop does is take each of the file names given by the ls command and store it in the $file_name bash variable. You’ll see this:-

   [raja@atreides test]$ for file_name in `ls data_file_*`; do echo "The file:" $file_name; done
   The file: data_file_1
   The file: data_file_10
   The file: data_file_2
   The file: data_file_3
   The file: data_file_4
   The file: data_file_5
   The file: data_file_6
   The file: data_file_7
   The file: data_file_8
   The file: data_file_9

4. Now that we’ve stored the file names in variables, we can use the sed command to edit it, replacing the underscores with a hyphen. I’ll echo the file name and pipe it to sed, to make sure it replaces the file name, and not modify the files itself.

   I used the sed replace command, s with a global option behind, the g, to make sure it replaces all occurrences of the underscore. Without the ‘g’, sed will only replace the first underscore and ignore the rest.

   for file_name in `ls data_file_*`; do echo "The file:" $file_name; echo $file_name | sed 's/_/-/g' ; done

   When you run this command in your console, you will see this output:

   [raja@atreides test]$ for file_name in `ls data_file_*`; do echo "The file:" $file_name; echo $file_name | sed 's/_/-/g' ; done
   The file: data_file_1
   data-file-1
   The file: data_file_10
   data-file-10
   The file: data_file_2
   data-file-2
   The file: data_file_3
   data-file-3
   The file: data_file_4
   data-file-4
   The file: data_file_5
   data-file-5
   The file: data_file_6
   data-file-6
   The file: data_file_7
   data-file-7
   The file: data_file_8
   data-file-8
   The file: data_file_9
   data-file-9

5. Of course, all this script is doing right now is editing the file name in the $file_name variable itself. Even though you can see what the modified file name will look like, we have not actually renamed the files on your hard disk yet. (This can be a good method of testing your sed-fu, before you really do it )
6. In order to actually rename the file, I’ll put the results of sed’s transformation in a variable called $new_file_name.I’ll also print this out to the terminal, so you can see the changes that are about to take place.

   for file_name in `ls data_file_*`; do echo "The file:" $file_name; new_file_name=$(echo $file_name | sed 's/_/-/g'); echo "New name:" $new_file_name ; done

   You’ll then see this being output on the terminal:

   [raja@atreides test]$ for file_name in `ls data_file_*`; do echo "The file:" $file_name; new_file_name=$(echo $file_name | sed 's/_/-/g'); echo "New name:" $new_file_name ; done
   The file: data_file_1
   New name: data-file-1
   The file: data_file_10
   New name: data-file-10
   The file: data_file_2
   New name: data-file-2
   The file: data_file_3
   New name: data-file-3
   The file: data_file_4
   New name: data-file-4
   The file: data_file_5
   New name: data-file-5
   The file: data_file_6
   New name: data-file-6
   The file: data_file_7
   New name: data-file-7
   The file: data_file_8
   New name: data-file-8
   The file: data_file_9
   New name: data-file-9

7. Now that we’ve got both the old AND new file names, nicely stored in variables, its time to actually rename them using the mv command. The syntax for renaming is mv current_file_name new_file_name. I think you’re starting to see where these variables come in handy.

   for file_name in `ls data_file_*`; do echo "The file:" $file_name; new_file_name=$(echo $file_name | sed 's/_/-/g'); echo "New name:" $new_file_name ; mv -v $file_name $new_file_name; done

   I’ve added a -v to the mv, so it displays what it is changing. As I always say, a little more verbosity is always good, especially on the terminal. Your final output will be something like this:-

   [raja@atreides test]$ for file_name in `ls data_file_*`; do echo "The file:" $file_name; new_file_name=$(echo $file_name | sed 's/_/-/g'); echo "New name:" $new_file_name ; mv -v $file_name $new_file_name; done
   The file: data_file_1
   New name: data-file-1
   `data_file_1' -> `data-file-1'
   The file: data_file_10
   New name: data-file-10
   `data_file_10' -> `data-file-10'
   The file: data_file_2
   New name: data-file-2
   `data_file_2' -> `data-file-2'
   The file: data_file_3
   New name: data-file-3
   `data_file_3' -> `data-file-3'
   The file: data_file_4
   New name: data-file-4
   `data_file_4' -> `data-file-4'
   The file: data_file_5
   New name: data-file-5
   `data_file_5' -> `data-file-5'
   The file: data_file_6
   New name: data-file-6
   `data_file_6' -> `data-file-6'
   The file: data_file_7
   New name: data-file-7
   `data_file_7' -> `data-file-7'
   The file: data_file_8
   New name: data-file-8
   `data_file_8' -> `data-file-8'
   The file: data_file_9
   New name: data-file-9
   `data_file_9' -> `data-file-9'

   An ls will reveal that all files have really been changed this time.

   [raja@atreides test]$ ls
   data-file-1   data-file-2  data-file-4  data-file-6  data-file-8
   data-file-10  data-file-3  data-file-5  data-file-7  data-file-9

   This should give you an idea on how to mass rename files. Of course there are probably better ways. Please do comment if you know some.

First, you’ll need to register for a free account at their site. Once you’ve chosen a domain name and setup your details, you’ll need a dynamic dns client to update your IP, which probably changes every time you sign on to your ISP.

I use inadyn, a free dynamic dns update client that works in linux.

The Inadyn package name is inadyn-mt. Install inadyn using yum:

yum install inadyn-mt

Then edit the /etc/inadyn.conf file with your details.

Then turn on the service.

service inadyn start

Check /var/log/messages. you should get some entires showing whether you edited the config file properly, and the update was successful.

Jul 10 22:50:43 atom INADYN[8251]: Fri Jul 10 22:50:43 2009: I:INADYN: Alias 'your-hostname.dyndns.org' to IP '12.34.56.78' updated successfully.

Once you know the client works, dont forget to turn it on permanently on startup.

chkconfig inadyn on

Use the awk command.

awk -F":" ' $3 > 200  {print $1} '  /etc/passwd

So, you’ve heard about the versatile port scanning tool called nmap and want to install it in Fedora Linux. The only problem is, you don’t know if it has been pre-packaged and is available as an rpm binary. No worries, all you need to do is search for using yum.

Use the yum search command.

yum search nmap

Based on its output, you know there are packages available, and all you need to do is yum install nmap

[raja@atreides ~]$ yum search nmap
Loaded plugins: fastestmirror, presto, refresh-packagekit
================================ Matched: nmap =================================
nmap.i586 : Network exploration tool and security scanner
nmap-frontend.i586 : the GTK+ frontend for nmap
onesixtyone.i586 : An efficient SNMP scanner
perl-Nmap-Parser.noarch : Parse nmap scan data with perl
psad.i586 : Port Scan Attack Detector (psad) watches for suspect traffic

Or, you might know that its called nmap, and want to search through you yum repositories to find if any of the available rpms have a file called nmap. To do that, use the yum provides */ command. e.g.

yum provides */nmap

[raja@atreides ~]$ yum provides */nmap
Loaded plugins: fastestmirror, presto, refresh-packagekit
2:nmap-4.76-4.fc11.i586 : Network exploration tool and security scanner
Repo        : fedora
Matched from:
Filename    : /usr/share/nmap
Filename    : /usr/bin/nmap

From this, you know that the nmap-4.76-4.fc11.i586 rpm contains these files, and by installing it, you get nmap.

1. Edit your /etc/rc.sysinit file, change line no 26 from

   mount -n -t usbfs /proc/bus/usb /proc/bus/usb

   to

   mount -t usbfs -o remount,devgid=$(awk -F: '/^vboxusers:/{print $3}' /etc/gr    oup),devmode=664 /proc/bus/usb /proc/bus/usb

   So, your /etc/rc.sysinit should change from:

    23 if [ ! -d /proc/bus/usb ]; then
    24         modprobe usbcore >/dev/null 2>&1 && mount -n -t usbfs /proc/bus/usb     /proc/bus/usb
    25 else
    26        mount -n -t usbfs /proc/bus/usb /proc/bus/usb
    27 fi

   to

    24         modprobe usbcore >/dev/null 2>&1 && mount -n -t usbfs /proc/bus/usb     /proc/bus/usb
    25 else
    26 #       mount -n -t usbfs /proc/bus/usb /proc/bus/usb
    27 mount -t usbfs -o remount,devgid=$(awk -F: '/^vboxusers:/{print $3}' /etc/gr    oup),devmode=664 /proc/bus/usb /proc/bus/usb
    28 fi

2. Next, edit your /etc/udev/rules.d/10-vboxdrv.rules. Change line number 1 from

   KERNEL=="vboxdrv", NAME="vboxdrv", OWNER="root", GROUP="root", MODE="0600"

   to

   KERNEL=="vboxdrv", NAME="vboxdrv", OWNER="root", GROUP="root", MODE="0660"

3. Reboot your machine. You should now be able to mount you usb devices.

The following screenshot shows some of the USB devices can allow my guest machine to view.

The USB devices available for VirtualBox Guests

Devices like my USB Flash Drive are still blurred out. In order to get them to work, I need to install the VirtualBox Guest Additions first.

Source:

VirtualBox Community Forum