unix

Today I spent large part of the day to configure a vpn to access our servers. Instead of leaving port 22 wide open, I prefer to use a vpn to access the internal network and to do ordinary administration tasks. This way I'll also be able to use graphical tools that I don't feel like to use over the internet.

This is data related with a dell 2950 + md1000 that I'm configuring. /dev/sda is the onboad raid controller with 3 300G sas disks (raid5). /dev/sdb is the md1000 with 5 1T sata disk (raid5). First when configuring the md1000 you must create the logical volume from the bios. I've created a fairly standard raid5 array using with all disks.

The crude data without any optimization is as follows:

<code lang=sh> promethium:~# hdparm -tT /dev/sda

/dev/sda: Timing cached reads: 5872 MB in 2.00 seconds = 2940.90 MB/sec

nc, TCP/IP swiss army knife, is an utility to transfer data across the network (actually is much more then that...). If you need to transfer large files inside you private network it might be a good idea to use nc, instead of heavier data transfer protocols (such as nfs, samba, ssh, http...)

Server side :

nc -vvn -l -p 3000 -w 3 | pv -b > outputfile


where -l says to listen and -p 3000 specifies the port.

Client side :


nc -vvn 192.168.0.5 3000 < inputfile


This is pretty straightforward.

To make the process a bit more human friendly I've used pv that is a small monitor the progress to show how much data has been transfered.

This is a small recipe to resize a disk image. In this case I wanted to make it bigger.

create a sparse file :

dd if=/dev/zero of=xen.img bs=1k count=1 seek=30M


copy the old file system to the sparse file:

dd if=old-xen.img of=xen.img conv=notrunc


now we resize the fs (reiserfs in this case)

resize_reiserfs xen.img


and we can happily mount it.

mount -o loop xen.img test/


now we have a bigger fs !

# df -h
Filesystem Size Used Avail Use% Mounted on
/home/xen.img 30G 338M 30G 2% /home/test


If I don't trust a stranger to wonder inside my house, why should I allow a closed source program to access my home directory ? Apart from the paranoia and conspiracy implications I decided to spend some time learning how to chroot skype (and iceweasel for that matter, since I don't really trust javascript, flash and the mozilla plugin model) in a chroot.

I started from this article :
http://www.debian-administration.org/articles/566

This recipe didn't work out of the box. This is mine:

Now step by step:
First we install the software. I'm working on a debian unstable...