Year: 2013

IT

IPv6 privacy

On most Linux distributions, the right hand part of the IPv6 address is based on the computer's MAC address. As your MAC address is fixed and (in theory) worldwide unique, your computer can be traced anywhere it goes online. While cookies track you all the time, stil having another tracker around is not desired.

The "IPv6 Privacy Extensions" fix this by giving you a regularly changed random IPv6 address.

To enable IPv6 Privacy Extensions, edit the file /etc/sysctl.conf and add these lines:

net.ipv6.conf.wlan0.use_tempaddr = 2
net.ipv6.conf.eth0.use_tempaddr = 2
net.ipv6.conf.all.use_tempaddr = 2
net.ipv6.conf.default.use_tempaddr = 2

Still, whenever you go online on a browser that carries your cookies/flash cookies/zombie cookies/supercookies, you may be identified. But at least, it's a little harder to track you.

© GeekLabInfo IPv6 privacy is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

Review: Belkin KVM Omniview 5216K – part 3

Tonight, it's time for part 3 of my Belkin Omniview IP 5216K KVM Switch

End 2010/begin 2011 I bought a Belkin KVM Omniview 5216K. When I first started to use is a few months later, it crashed so often that the device was useless. And if accidentilly, I could connect, keys got stuck so often that typing my username or password was absolutely impossible.

With one of the required reboots, the device finally died on june 17 of that year. After having to deal with a terrible helpdesk that answered things that resemble "so, your car crashed into a canyon? Have you tried to restart your car to fix this?" and weeks of waiting, it finally got replaced by a 32 port switch, the Belkin Omniview IP 5232K KVM Switch..

Since the new device has a new firmware, the stuck keys got a little better. But another problem came up. I just tried to login to the device. And I definitely used the right password. The device is only accessible over VPN, so it's very unlikely that someone else got access to the device. And last time, I had this problem, the device just needed a restart to recognise my password again.

Probably the internal authentication daemon has died or something.

© GeekLabInfo Review: Belkin KVM Omniview 5216K – part 3 is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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Business

How to decrypt a PDF file on Linux

Sometimes, I receive digital invoices in PDF format with a password. That way I shouldn't be able to modify them and commit fraud. Unfortunately, this also makes it impossible to perform normal operations on them, such as removing unneeded specifications or merging all invoices into one single file.

Luckily, most Linux distributions come with a tool that can be used to remove these passwords: ghostscript.

In order to remove the password, simply run:

gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=unencrypted.pdf -c .setpdfwrite -f encrypted.pdf

While this does remove the password, I'm not sure if it does not degrade the quality of the file a little (I don't notice any quality difference, but if you use highres files, you may lose quality).

© GeekLabInfo How to decrypt a PDF file on Linux is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

Manually undeleting a file from ext2, ext3, ext4 or any other filesystem

Yesterday, I worked on a PHP project all day. At the end of the day, I moved it from development to staging. And finally I deleted it from staging. Oops!

I just discovered an hour ago what I did. What to do, what to do...?

Back in the old days, Midnight Commander supported some undelete function, but this option has been removed in the CentOS 6 version I'm running.

Then there's the option to use extundelete, but that would need compiling and a lot of other disk activity before I could use it. Normally, I would compile such a program on another server, then hook up the disk. But since it's a cloud server that I cannot access in any other way but SSH, that's not an option.

And finally there's the option to use ext3undel+foremost+testdisk from rpmforge to undelete information, but somehow I couldn't get all dependencies to install. So there's no usable software to fix this.

Or is there?

Manual recovery

Most filesystems, except for filesystems that do raid/compression/encryption, just write data to blocks on the disk in a structured manner. If you could save and access the blocks, you may be able to do some manual recovery.

Continue Reading…

© GeekLabInfo Manually undeleting a file from ext2, ext3, ext4 or any other filesystem is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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IT

WiFi on a HP Elitebook 8570w

There once was a day that I compiled my own kernels and configured all modules manually. It's been quite a while since I've done anything like that, but I remembered some of it.

Today I installed my WiFi drivers. The HP Elitebook 8570w I own has a Centrino Advanced-N 6205 on board that is actually supported by Fedora 17.

$ lspci
00:00.0 Host bridge: Intel Corporation Ivy Bridge DRAM Controller (rev 09)
00:01.0 PCI bridge: Intel Corporation Ivy Bridge PCI Express Root Port (rev 09)
00:14.0 USB Controller: Intel Corporation Panther Point USB xHCI Host Controller (rev 04)
00:16.0 Communication controller: Intel Corporation Panther Point MEI Controller #1 (rev 04)
00:19.0 Ethernet controller: Intel Corporation 82579LM Gigabit Network Connection (rev 04)
00:1a.0 USB Controller: Intel Corporation Panther Point USB Enhanced Host Controller #2 (rev 04)
00:1b.0 Audio device: Intel Corporation Panther Point High Definition Audio Controller (rev 04)
00:1c.0 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 1 (rev c4)
00:1c.1 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 2 (rev c4)
00:1c.2 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 3 (rev c4)
00:1c.3 PCI bridge: Intel Corporation Panther Point PCI Express Root Port 4 (rev c4)
00:1d.0 USB Controller: Intel Corporation Panther Point USB Enhanced Host Controller #1 (rev 04)
00:1f.0 ISA bridge: Intel Corporation Panther Point LPC Controller (rev 04)
00:1f.2 SATA controller: Intel Corporation Panther Point 6 port SATA AHCI Controller (rev 04)
00:1f.3 SMBus: Intel Corporation Panther Point SMBus Controller (rev 04)
01:00.0 VGA compatible controller: nVidia Corporation Device 0ffc (rev a1)
01:00.1 Audio device: nVidia Corporation Device 0e1b (rev a1)
24:00.0 FireWire (IEEE 1394): JMicron Technology Corp. IEEE 1394 Host Controller (rev 30)
24:00.1 System peripheral: JMicron Technology Corp. SD/MMC Host Controller (rev 30)
24:00.2 SD Host controller: JMicron Technology Corp. Standard SD Host Controller (rev 30)
25:00.0 Network controller: Intel Corporation Centrino Advanced-N 6205 (rev 34)

The device at the very bottom is the WiFi device we're looking for. But iwconfig shows it's not available to the system somehow:

$ iwconfig
thuisf    no wireless extensions.
 
vmnet8    no wireless extensions.
 
thuis     no wireless extensions.
 
eth0      no wireless extensions.
 
lo        no wireless extensions.
 
virbr0-nic  no wireless extensions.
 
virbr0    no wireless extensions.
 
noc       no wireless extensions.
 
vmnet1    no wireless extensions.

Continue Reading…

© GeekLabInfo WiFi on a HP Elitebook 8570w is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info

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