Category: Linux


As we saw earlier, Rsync can be a nifty tool to transfer data across the systems in an organization while taking backup. However, its prompt for password during transfers can irritate everytime you transfer. Even having a cron-job for automatic backups using rsync will mean you having to enter password which defeats the purpose of cron-job. Here I will show you how you can use rsync over ssh to sync data across computers without password. That’s right, password less transfers with rsync.

First on your server(IP:192.168.100.101) create a ssh key using ssh-keygen,

#ssh-keygen

It will ask you for a location, hit enter for the default location. Next you’ll be prompted for a pass-phrase, hit enter & confirm it with another enter. We want the pass-phrase to be blank. You’ll get the following.

Generating public/private rsa key pair.
Enter file in which to save the key (root/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /root/.ssh/id_rsa.
Your public key has been saved in /root/.ssh/id_rsa.pub.

Next we will need to copy the public key to the remote system(192.168.100.102). On the local system(192.168.100.101) enter the following;

#ssh-copy-id -i /root/.ssh/id_rsa.pub 192.168.100.102

You’ll be prompted for password for the remote system. Once you enter it, the key will be copied on the remote host. Now you can use rsync to connect & transfer to the remote system(192.168.100.102) without any password prompt.

#rsync -avz -e ssh /root/Desktop/test root@192.168.100.102:/root/Desktop

Now the transfer will be commenced without any prompt for password. You can transfer your public key to various other systems on your network to facilitate a password-less rsync over ssh.

At times, we need to combine multiple pdf file’s into one pdf file. However, instead of running to get a dedicated program to join the multiple pdf’s, here is a simple & fast way to do so.

Convert command can be used to merge multiple pdf’s into one. Convert command is a subset of the ‘ImageMagick’ suite of tools. So you’ll need to install it first from your distribution’s repository. On a Fedora/Red Hat system it can be done by;

#yum install ImageMagick

Once installed, simply open a terminal & navigate to the directory where you have the multiple pdf’s which need to be merged into one pdf. Once there issue;

$convert file1.pdf file2.pdf output.pdf

I created a calendar for the coming year & in all had 12 pdf’s for each month which I wanted to be merged into one. Hence, I issued the following;

$convert Jan.pdf Feb.pdf March.pdf April.pdf May.pdf June.pdf July.pdf August.pdf September.pdf October.pdf November.pdf December.pdf calendar.pdf

Here my output pdf file will be named ‘calendar.pdf’. Once you execute the above command, it will take sometime(depending on how big or small & how many pdf’s are) and once done it will return you to the prompt. Now your merged pdf file will be saved in the same folder by the name you gave in the command above.

That’s it! It’s so easy.

RSync is useful for fast incremental transfer of data. It is very popular across business organizations as it comes with some pretty handy features which sets it apart from the rest. Some of them are;

1) Security – One can transmit the data using the ssh tunneling which provides encryption & safety from eavesdroppers.

2) Speed – Since rsync transmits only the data which has changed over subsequent time, the transmission is fast as only the bits which are changed are transferred & not the entire file. This can mean tremendous saving of time. It also comes with options which lets you fine-tune the transfer which can further improve the transfer speed.

3) Less Bandwidth Intensive – Rsync uses compression & decompression algorithms at the sending & receiving end respectively. This not only speeds up the transfer but also saves the bandwidth.

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Install Cisco Packet Tracer under Linux

Cisco Packet Tracer can be a very useful tool for learning about networking without needing to spend tons of money(infact, none). The simulator allows you to create a networking topology & then carry on your configurations & changes before they can be implemented in the real world networking environment. This is critical as you get to learn from any mistakes in simulation thus not needing your network to act as a guinea pig. Here, I’ll show you how you can install the Cisco Packet Tracer under your linux system. I would be installing it on Fedora 18.

Cisco Packet Tracer Linux

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The ‘Recent’ item under places in nautilus sidebar can be handy for accessing recent files on the system. However it can also be a privacy breach. There seems no easy setting to hide the ‘recent’ entry under places. Hiding the sidebar option will hide it completely. Here is a way to hide the ‘recent’ places under the file manager. Actually this does not hide the recent places, but does not allows any files to be listed there in the first place. After doing the following, you’ll see the ‘recent’ under places but there won’t be files listed in there.

The items shown under the recent are stored in a file which is dynamically modified as the user access the files over the system. Simply delete the file containing the recent items history using the following command.

$rm -rf ~/.local/share/recently-used.xbel

Now you’ll need to logout & relogin for changes to take effect. However this is only a one time solution. You’ll need to manually run this command from time to time to clear the recent items.

If you want to save this hassle, you can do the following changes to clear the recent items from not showing up at all. A permanent fix would be to first delete the above file. Now immediately before you open any of your documents(audio, video, text or any file), open a terminal & do the following.

$cd ~/.local/share/

$touch recently-used.xbel

$su

#chattr +i recently-used.xbel

That’s it & you’re done. Now ‘recent’ items under the sidebar will always be empty. To know more about the chattr command, read this post.

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