Juste quelques mots en Wolof que j’ai appris aujourd’hui:
[beu soubeu] -> a demain[beu lundi] -> a lundi[kokala] -> qui c’est ? (aggressif)Aprés la korité, aprés la tabaski, on se souhaite la bonne année:
[dewenati] -> bonne année[fakeldewan] -> a l’année prochaine !This howto explain how to use rsync to build a data mirroring mechanism on a local machine, with two hard drives, ala RAID 1, but without RAID 1 (!).
I had the project to setup a RAID 5 array using 3*120 Gb hard drives in USB enclosures. Unfortunately my project stalled due to instability in early 2.6.x kernels (I heard that 2.6.12 and upper are now useable for “RAID over USB”).
Because of the urgency of reliable storage (and because I don’t want to waste time compiling and fine-tuning kernels), I decided to do it using traditionnal IDE host. So I plugged two 120Gb HDD on my machine as master device, one on each IDE channel.
Then I made a big XFS partition on each, and update my /etc/fstab:
/dev/sda1 / auto noatime 1 1 /dev/hda1 /mnt/hd1 xfs defaults 1 2 /dev/hdc1 /mnt/hd1_mirror xfs defaults 1 2
At that moment I have to explain you that my machine is an OpenBrick NG, with a USB 2.0 512 Mb thumb drive (/dev/sda1 in the fstab) on which all my linux system is installed. That explain why my two IDE channels are free for use.
The idea is now to use /mnt/hd1 to store and manipulate my datas, then rsync that drive with his alter-ego (/mnt/hd1_mirror) every night. To do that, I’ve just added the following command in a cron entry:
rsync -a --delete --delete-excluded --delete-after /mnt/hd1/ /mnt/hd1_mirror/
And voilà !
As you guess, this solution is far from perfect, and has major inconvenients regarding RAID 1:
Oh, and by the way, be careful to not write files on /mnt/hd1_mirror/ because they will be deleted each night during the mirroring process.
Get the last stable source code archive on xvidcap Sourceforge project page or download it from the CVS:
cvs -z3 -d:pserver:anonymous@cvs.sourceforge.net:/cvsroot/xvidcap co -P xvidcap
Install required dependencies:
urpmi gcc automake libgtk+2-devel ffmpeg-devel liblame0-devel
Dirty compile:
make distclean [optional] CPPFLAGS=-I/usr/include/ffmpeg LDFLAGS=-L/usr/bin/ffmpeg ./configure --with-gtk2 --with-forced-embedded-ffmpeg && make gvidcap make gvidcap make install [optional]
Quick test:
./src/gvidcap &
Raw capture:
gvidcap --gui no -v --file ~/img_%04d.xwd --frames 0 --fps 10 --cap_geometry 1024x768+0+0
The following can be used but it slow down the machine (png compression require too cpu):
gvidcap --gui no -v --compress 9 --file ~/img_%04d.png --frames 0 --fps 10 --cap_geometry 1024x728+0+0
Convert .xwd images to .png images because mplayer only support .png, .jpg, .tga and .sgi image file format:
convert img_*.xwd img_%04d.png && rm -rf ./*.xwd
Preview the video:
mplayer "mf://*.png" -mf fps=10
Make a video from successive screenshots:
mencoder "mf://*.png" -mf fps=10 -ovc lavc -o ./video.avi
Documentation:
Create a file /etc/qemu-ifup that contain:
#!/bin/sh sudo modprobe tun sudo /sbin/ifconfig $1 up 10.0.2.2 netmask 255.255.255.0 broadcast 10.0.2.255 # IP masquerade sudo echo "1" > /proc/sys/net/ipv4/ip_forward sudo /sbin/iptables -N nat sudo /sbin/iptables -t nat -F sudo /sbin/iptables -t nat -A POSTROUTING -s 10.0.2.15 -j MASQUERADE sudo /sbin/iptables -t nat -A POSTROUTING -d 10.0.2.15 -o $1
Don’t forget to give it execution permissions:
chmod 755 /etc/qemu-ifup
Start qemu with the following parameters:
qemu /home/kevin/qemu-mdk10.1.img -n /etc/qemu-ifup
Setup the network in your ghest OS in qemu:
ifconfig eth0 10.0.2.15 route add default gw 10.0.2.2
Test the visibility of the guest OS from the host OS:
[root@localhost kevin]# ping 10.0.2.15 PING 10.0.2.15 (10.0.2.15) 56(84) bytes of data. 64 bytes from 10.0.2.15: icmp_seq=1 ttl=64 time=2.96 ms 64 bytes from 10.0.2.15: icmp_seq=2 ttl=64 time=0.295 ms 64 bytes from 10.0.2.15: icmp_seq=3 ttl=64 time=0.296 ms --- 10.0.2.15 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2000ms rtt min/avg/max/mdev = 0.295/1.185/2.965/1.258 ms
Test the visibility of the host from the guest:
[root@localhost root]# ping 10.0.2.2 PING 10.0.2.2 (10.0.2.2) 56(84) bytes of data. 64 bytes from 10.0.2.2: icmp_seq=1 ttl=64 time=1.08 ms 64 bytes from 10.0.2.2: icmp_seq=2 ttl=64 time=0.433 ms 64 bytes from 10.0.2.2: icmp_seq=3 ttl=64 time=0.383 ms --- 10.0.2.2 ping statistics --- 3 packets transmitted, 3 received, 0% packet loss, time 2001ms rtt min/avg/max/mdev = 0.383/0.634/1.087/0.321 ms
Some useful command to help running and setup qemu…
qcow2 format):qemu-img create -f qcow2 /home/kevin/qemu-disk-image.qcow 10G
qemu -cdrom /dev/cdrom -hda /home/kevin/qemu-disk-image.qcow -boot d
iso image:qemu -cdrom /home/kevin/ubuntu.iso -hda /home/kevin/qemu-disk-image.qcow -boot d
qemu /home/kevin/qemu-disk-image.qcow
qcow image to a raw image:qemu-img convert /home/kevin/qemu-disk-image.qcow -O raw /home/kevin/qemu-disk-image.raw
mount -o loop,offset=32256 /home/kevin/qemu-disk-image.raw /media/qemu/
qcow2 disk image via the nbd protocol (don’t forget to install the nbd-client package):modprobe nbd max_part=63 qemu-nbd -c /dev/nbd0 /home/kevin/qemu-disk-image.qcow2 mount /dev/nbd0p1 /media/qemu
qemu-system-x86_64 binary command instead of qemu.We have a USB key with a file system on it, and we want to save its content. We do a binary image using:
dd if=/dev/sda1 of=/home/kevin/usb_key.img
Get informations about the file system of the image file using:
fdisk -l -u /home/kevin/usb_key.img
This show you something like that:
Disque usb_key.img: 0 Mo, 0 octets 9 têtes, 56 secteurs/piste, 0 cylindres, total 0 sectors Unités = secteurs de 1 * 512 = 512 octets Périphérique Boot Start End Blocks Id System usb_key.img1 56 511559 255752 83 Linux
Get the sector number where the partition start (56) and the size of sectors (512). Multiply the two values:
56 * 512 = 28672
Then setup a loopback block device based on the image:
losetup -o 28672 /dev/loop0 /home/kevin/usb_key.img
Now you can mount your USB key:
mount /dev/loop0 /mnt/usb_key/
