sudo aptitude install pdftk
(if you run Fedora, RedHat or CentOS use this one: sudo yum install pdftk)

Split large pdf into many one-page files:

pdftk largepdfile.pdf burst

(as the result you will get many small files like pg_0001.pdf, pg_0002.pdf and so on).

Merge files into one PDF file:

pdftk *.pdf cat output onelargepdfile.pdf

pdftk is extremely powerful and makes it possible to do almost anything with input pdf files. Thus above two commands are just examples showing how to split and merge pdf files in Ubuntu easily.

Rather long preface but solution is quite simple. If u run Ubuntu you can try lxsplit utility for breaking files into parts (binary packages for other Linux distributions as well as source code are available at lxsplit project’s homepage.):

sudo apt-get install lxsplit

In order to split some file in 3.99GB parts use the following command:

lxsplit -s /path/to/hugemoviefile.mkv 3999M

Depending on size of hugemoviefile.mkv you will get several parts hugemoviefile.mkv.001, hugemoviefile.mkv.002 and so on stored in current directory. It means that if you’re going to store those parts on some external storage like ipod you can do the following:

cd /media/ipod/
lxsplit -s /path/to/hugemoviefile.mkv 3999M

and hugemoviefile.mkv.001.. will saved in /media/ipod/ directory regardless where hugemoviefile.mkv is located.

Now coming to assembling procedure. It’s just as easy as splitting:

lxsplit -j hugemoviefile.mkv.001

Once done you will get hugemoviefile.mkv saved in current directory.

Have an interesting article? You’re welcome to contact me and get it published at LinuxScrew.com!

Anyways sometimes Packet Tracer as like as dynamips/gns3 are not a panacea when it’s necessary to emulate mid-sized network or test some specific ios features on real Cisco devices. There are several options: the first and the easiest one means to buy Cisco device. But we all know that Cisco’s pricing policy is far away from democratic in application to individual users so even used or refurbished Cisco router/switch will cost enough to think about another option. Second option is to schedule access to Community Lab at packetlife.net. Nice to know the access to it is absolutely free so anyone can get logon to Cisco routers, switches or ASAs once user reached his/her timeslot. Here is the list of hardware you can have access to (there are multiple devices of the same model):

Cisco ASA 5505
Cisco 2811 (2xWIC-2T)
Cisco 1841 (1xWIC-2T)
Cisco Catalyst 3550-24

Not bad for free lab as for me. The lab is broken into two blocks so user can reserve only one block or both blocks simultaneously. This is to make it possible to access the lab by multiple users simultaneously. Devices are connected to each other according to predefined topology — see separate diagrams for Ethernet and Serial connections below (they are split to prevent overhead on the graph I guess). All documentation as well as FAQs can be found here: here and here. Thanks to Jeremy Stretch.

P.S. By the way if you can share any other similar labs allowing people on the web to access Cisco (or some other networking devices) — you are welcome to share this information here. Thanks!

Truecrypt is cross platform disk/file encryption software that is available for windows, mac os and linux. In order to get started visit www.truecrypt.org site and download the latest version of this software (direct link) and install it:

cd /usr/src
sudo -s
wget -c http://www.truecrypt.org/download/truecrypt-6.3a-linux-x86.tar.gz
tar -xvzf truecrypt-6.3a-linux-x86.tar.gz
./truecrypt-6.3a-setup-x86
exit

When installation is finished you will see Trucrypt item in Gnome menu (if not or use different X manager — type truecrypt in command line). Here how it looks like:

In order to create encrypted file press “Create Volume” button and follow instructions:

Use long passwords like “e07910a06a086c83ba41827aa00b26ed” instead of “123″ or “iloveyou”:

Once encrypted candy is created you can store it on usb flash drive or elsewhere, it doesn’t matter how that storage is formatted — it can be CD or windows formatter ipod.

Use the same utility to open the file — press “Select File” and point to newly created encrypted file, then choose first slot and select “Mount Volume” in drop down menu (it will ask for your sudo password and then password you typed when created the file):

As the result encrypted filesystem will be mounted into /media/truecrypt1 directory:

Copy your sensitive files there and unmount /media/truecrypt1 when done (select “Dismount” in drop down menu).
Good luck!

Currently it is available as a beta so every time Google upgrades their google-chrome-beta_current_i386.deb package you will need to download fresh one and install it again over existing package. This is not so effective as using apt package manager with Google Chrome repository for easy installation and automatic upgrades.

Once you installed Ubuntu Lucid Lynx on your computer and connected it to Internet open terminal (command line) and type there the following:

sudo aptitude update
sudo aptitude install google-chrome-beta

This will install the latest version of Google Chrome (Chromium) browser and also will keep it up to date (Ubuntu checks for updates periodically and will notify you if fresh packages are available). Instead of using command line you can try Synatic Package manager that comes with Ubuntu Lucid Lynx by default and makes it possible to select packages to install without any commands. To open it go to System –> Administration –> Synaptic Package Manager, mark google-chrome-beta for installation and press Apply button. In a few minutes Google Chrome will be installed and appear in Applications –> Internet Gnome menu.

As for me Chrome is much more faster than other browser I’ve been using for a long time like Firefox and Opera but due to lack of extensions I wouldn’t recommend Google Chrome as primary browser. The most important extension for me is Nagios checker that is still in early stage of development for Chrome. Anyway here is official repository of Chrome extensions: https://chrome.google.com/extensions, there are not so many plugins as for Firefox but growing.

Good browsing with Google Chrome!

For rather long time I’ve been using gtkpod, amarok, banshee, exaile or rhythmbox to sync my ipod under Linux/Ubuntu and load my music collection there. As we all know The Elder Brother Apple fights with interoperability and makes ipod/iphone users to use iTunes only. Any other applications that can read/write to ipod data format are prohibited by Apple. This also concerns Rockbox and ipod4linux alternative firmwares — once Apple encrypted ipod firmware it became impossible to use them. It definitely sucks. At least due to the fact there are millions of Linux users who are real or potential customers of Apple products. Anyways these facts have been discussed in various forums, blogs like this and similar but this post about how to install Windows as the second operating system along with Ubuntu or any other Linux.

The first that we need to do is to create new partition for Windows and format it to NTFS. Exact steps to accomplish this depend on your HDD partition table e.g. there is one large ext3/ext4 partition for Ubuntu or there are several partitions for various distributions or mount points. Anyway you should use partition manager to create and/or format NTFS partition. I use gparted. It is graphical and it just works (use ‘sudo apt-get install gparted‘ if you run Ubuntu/Debian).

Second you should backup your MBR record and restore it after Windows installation that silently erases existing bootloader and installs windows one, use “dd if=/dev/sda of=/mbr.bin bs=446 count=1” to save MRB into mbr.bin file and “dd if=/media/sda/mbr.bin of=/dev/sda bs=446 count=1” to restore it from file to HDD.

To sum everything up here is the algorithm:

0. BACKUP ALL YOUR DATA!
1. Create NTFS partition using gparted.
2. Backup MBR using dd command e.g. “dd if=/dev/sda of=/mbr.bin bs=446 count=1″ (/dev/sda means your HDD).
3. Boot Windows installation CD and install it onto newly created NTFS partition.
4. Boot into Linux live CD  e.g. Ubuntu Live CD.
5. Restore MBR using dd e.g. “dd if=/media/sda/mbr.bin of=/dev/sda bs=446 count=1″.
6. Reboot.
7. Select Ubuntu in grub menu and boot it.
8. Setup grup for Windows booting.

In order to accomplish the last 8th item you should add the following text block to the end of grub config (read this article for detailed information):

title Microsoft Windows XP
root (hd0,1)
savedefault
makeactive
chainloader +1

Good luck!

P.S. If something goes wrong or you need more details you can take a look at the following article at ubuntu.com: Recovering Ubuntu After Installing Windows. It’s written in rather tangled manner but still informative.

Today it came to my mind that it is time to make sensitive information stored on my usb flash drive encrypted but still transportable and easy to use. But I don’t want to have whole my 32 GB usb drive fully encrypted using truecrypt or something similar. It is just toooo slow. I also don’t want to use GPG for uncompressing files and directories every time I would like to read them and then create new GPG compressed file every time I save changes. This eats too much of my time and system resources. At the same time it is necessary to be able to use that usb drive under windows, mac, linux whatever (read/write files) but still have my directory structure with sensitive files encrypted. Here is the solution: create encrypted filesystem within a file named, say, 16GB.candy.bin that could be stored on regular windows formatted usb flash drive and then mounted under Linux using the password.

When it becomes necessary I can mount that 16GB.candy.bin as the regular ext3 filesystem with all those stuff like permissions, ownership etc. that is available on ext3 but not in FAT or NTFS. On my windows formatted flash drive candy takes only 16 GB so I can use the rest of space to store not so sensitive information like mp3, movies or photos. Moreover I on windows or linux to read it.

Let’s create that 16GB.candy.bin file with encrypted ext3 filesystem (read below explanations below carefully before just to copy/paste commands into CLI):

[root@artemn root]# cd /path/to/candy/

[root@artemn root]# tune2fs -i 0 -c 0 /dev/loop0

Here are some points: using above commands we create encrypted file of 16 GB so if you need to have more or less just change “count=16000″ in dd line. “count=16000″ means 16GB so “count=20″ means 20MB. Path ‘/path/to/candy/’ is for example only so you should change it to real directory that is able to host encrypted file (16 GB in above example). Command losetup is present in most Linux distributions (btw I recommend Ubuntu especially newly released Lucid Lynx) but if it is not use your disro’s packet manager to install it or compile from sources (for super geeks only, Mr. Stallman if you read this article — Hello). Reader, you can replace “/dev/urandom” in dd line with “/dev/zero” that will make that command to finish faster but will lower security level of resulting file (read about AES for better understanding). You will need to enter the password when running losetup command so make sure it safe and long enough like ‘6U2sAsR37Hn8122dGsaPrew1twt’ but not ‘abc123′ or ‘iloveyou’.

Once commands are done you will get 16GB.candy.bin containing encrypted ext3 filesystem. You can store this file where ever you want, say, on a flash drive. If you loose it nobody won’t be able to open it until he (or she!) cracked AES encryption (use long passwords to prevent this). As the next step it is required to mount filesystem and store some files/directories in it:

[root@artemn root]# mkdir -p /mnt/candy

[root@artemn root]# umount /mnt/candy

When you unmount 16GB.candy.bin the changes are already saved there so it’s not required to compress and encrypt anything unlike with GPG.

P.S. This post is inspired by Loopback tricks article. Thanks to the author. Good luck!

# mkdir /tmp/ramdisk; chmod 777 /tmp/ramdisk
# mount -t tmpfs -o size=256M tmpfs /tmp/ramdisk/

where 256M is amount of RAM you wish to allocate for ramdisk. It’s clear that this value should be less than amount of free memory (use “free -m“). BTW, if you specify too many MBs for ramdisk Linux will try to allocate it from RAM and then from swap so resulting performance would be very poor.