Octopress is quite popular among opensource developers since its include all the features needed to maintain a simple blog plus some extensions like source code syntax hilight, social networks integrations and support to deploy on GitHub Pages and Heroku (both free).

I should say that Octopress isn’t a CMS as many of you can imagine, but a static html pages generator. This may sounds oldie, but Octopress leverage some existing tools, and you will like it.

The following is a Google Webmaster graph, the performance gain was from an average of 600 ms for page retrivial with Drupal (with caches) to an average of 120 ms with Octopress.

To migrate existing posts from Drupal 7, I’ve used a slightly modified version of an existing migration script. Put your mysql connection details and execute it, it will generate a bunch of files to put inside the source/_posts folder of your Octopress.

On 26 Novembre 2012 I carried out a workshop, sponsored by Develer (offering space, organization and drinks), that attracted quite many people around the Florence area, spending a nice evening discussing about Cloud Computing with OpenNebula.

The presentation covered some basic topics, like what OpenNebula is and why users should use it, and continued with a live demo using the OpenNebula Sandbox VM.

An alternative and effective method to deliver the short status notification is via Twitter messages, using a protected account (for privacy).

Register a new standard Twitter account and make sure to enable in the settings:

We need to install on the monitoring server a command-line Twitter client, such as Twidge:

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sudo apt-get install twidge

Do the one-time configuration procedure with the user you prefer:

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twidge setup

Move the generated configuration file from your home folder somewhere into the nagios/icinga configuration folder:

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sudo mv ~/.twidgerc /etc/icinga/twidgerc

Now add two new custom commands in the nagios/icinga configuration:

/etc/icinga/commands.cfg:

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define command {
        command_name  notify-host-by-twitter
        command_line  /bin/echo "HOST $HOSTALIAS$ is $HOSTSTATE$" | twidge -c /etc/icinga/twidgerc update
}
define command {
  command_name    notify-service-by-twitter
  command_line    /bin/echo "SERVICE $SERVICEDESC$ on $HOSTALIAS$ is $SERVICESTATE$" | twidge -c /etc/icinga/twidgerc update
}

Now you need to use such commands as host and service notifications, like here:

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define contact {
        contact_name                    root
        alias                           Root
        service_notification_period     24x7
        host_notification_period        24x7
        service_notification_options    w,u,c,r
        host_notification_options       d,r
        service_notification_commands   notify-service-by-twitter
        host_notification_commands      notify-host-by-twitter
}

Reload and enjoy!

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sudo /etc/init.d/icinga reload

The proposed solution includes a virtualization stack running on commody hardware, using the Linux KVM hypervisor, managed by Proxmox 2.0 and with a GlusterFS shared storage.

I hope to write down some article to share the most interesting bits of this configuration, but time is not our friend.

Here are the slides of the presentation “Open low-cost HA cluster cloud”, hoping that they will satisfy your curiosity:

Thanks to everyone who helped us in this journey!

cannot create ‘tank’: one or more vdevs refer to the same device, or one of the devices is part of an active md or lvm device

Obviously I’ve removed the device from the old mdadm array with:

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sudo mdadm /dev/md3 --set-faulty /dev/sdb3
sudo mdadm /dev/md3 --remove /dev/sdb3

However, the zpool utility doesn’t actually look if the device is currently used or not, but simply look at the metadata at the beginning of the disk that is still there.

To wipe the mdadm metadata you need to use:

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sudo mdadm --zero-superblock /dev/sdb3

But the good old dd will do the job too:

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sudo dd if=/dev/zero of=/dev/sdb3 count=64 bs=1024

We can use it as a drop-in replacement for the well-known tmpfs (used for speeding up compilation tasks or for /tmp), or better as a primary swap device, that will lead to virtually increase memory capacity, at the expense of a slightly increased CPU usage to compress/decompress the swapped data.

Nowadays RAM is very cheap, so why bother with compression? Because there are some situations where you can’t upgrade memory (netbooks) or you want to over-commit real resources (virtualization hosts).

For Ubuntu Precise and later:

Starting with Ubuntu Precise, there is an official upstart script for Ubuntu by Adam Conrad to configure zram in the main repository:

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sudo apt-get install zram-config

For other distributions or older Ubuntu:

Googlin’ around to find a nice way to configure zram devices as swap, I found a very nice upstart script that will create a bunch of ramz devices depending on the number of CPU cores available, with a total size of the available memory: https://raw.github.com/gionn/etc/master/init.d/zram

Copy the script to the init.d folder, mark it as executable and enable autostart on boot:

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sudo wget https://raw.github.com/gionn/etc/master/init.d/zram -O /etc/init.d/zram
sudo chmod +x /etc/init.d/zram
sudo update-rc.d zram defaults

Try it manually executing it for the first time with:

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/etc/init.d/zram start

Depending on the kernel version you are running, you may need to adjust the module parameter name to num_devices on line 26 to:

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modprobe zram num_devices=$num_cpus

or keep as is for newer kernels:

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modprobe zram zram_num_devices=$num_cpus

Checking if it’s working

If everything went smooth, you will find a few notices on dmesg:

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zram: module is from the staging directory, the quality is unknown, you have been warned.
zram: Creating 4 devices ...
Adding 1497864k swap on /dev/zram0.  Priority:100 extents:1 across:1497864k SS
Adding 1497864k swap on /dev/zram1.  Priority:100 extents:1 across:1497864k SS
Adding 1497864k swap on /dev/zram2.  Priority:100 extents:1 across:1497864k SS
Adding 1497864k swap on /dev/zram3.  Priority:100 extents:1 across:1497864k SS

meaning that the zram device have been created and enabled as swap devices with highest priority.

You can discover the increased swap space available with free -m:

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         total       used       free     shared    buffers     cached
Mem:          5851       5696        154          0         85       4310
-/+ buffers/cache:       1300       4550
Swap:         5851          0       5850

Happy zramming!

Read Reddit comments

These includes: * Desktop migration to Ubuntu Linux (10.04 LTS) with centralized login management (OpenLDAP) and shared /home with MooseFS; * OpenNebula KVM-based Cloud with MooseFS as backend storage (and publishing of the relative transfer manager: https://github.com/libersoft/opennebula-tm-moosefs); * GlusterFS-based infrastructure for the national italian legal deposit of books (italian article: http://www.bncf.firenze.sbn.it/pagina.php?id=212&rigamenu=Magazzini%20Digitali)

Installing ZFS on Debian/Ubuntu is straightforward: you need first to build the SPL (Solaris Porting Layer) and after ZFS itself.

Download the latest SPL package, unpack it and build:

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sudo apt-get install build-essential gawk alien fakeroot linux-headers-$(uname -r)
./configure
make deb
dpkg -i *.deb

Download the latest ZFS package, unpack it and build:

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sudo apt-get install zlib1g-dev uuid-dev libblkid-dev libselinux-dev parted lsscsi
./configure
make deb
dpkg -i *.deb

ZFS is now ready to be used.

Let’s create our first pool with:

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zpool create tank raidz [devices]

Devices can be partitions, UUIDs or entire disk. Is often a very good practice to use an entire disk using the disks id as found on /dev/disk/by-id/* (it should be advisable to not mix up existing drives with one of an existing volume).

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sudo zpool status tank
df -h

Check pool status. :)

Now, the interesting features:

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zfs set compression=on tank
zfs set dedup=on tank

Et voilà, your space usage is highly optimized compressing and deduplicating data.

Now it’s the GlusterFS turn, download the latest version and install it:

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dpkg -i glusterfs_3.2.2-1_amd64.deb
update-rc.d glusterd defaults
/etc/init.d/glusterd start

Only on one node do the peer probing for every peer:

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gluster peer probe ip.add.re.ss

Only on one node, create and start the volume:

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gluster volume create gtank replica 2 transport tcp ip.add.re.ss1:/tank ip.add.re.ss2:/tank
gluster volume start gtank

On every node, mount it with:

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mount -t glusterfs localhost:/gtank /gtank

Now some live example:

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root@debz-1:/gtank# df -h
File system           Dim. Usati Disp. Uso% Montato su
[..]
tank                   10G  1,8G  8,2G  18% /tank
localhost:/gtank       10G  1,8G  8,2G  18% /gtank

GlusterFS replica 2 on 2 servers, anything unexpected here.

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root@debz-1:/gtank# ls -lh
totale 1,8G
-rw-r--r-- 1 scorp scorp  253K  1 gen  1980 Fattura Garanzia redcoon dns-323.pdf
-rw-r--r-- 1 scorp scorp   68K  1 gen  1980 fattura scontrino eeepc 900a.pdf
-rw-r--r-- 1 scorp scorp   55K  1 gen  1980 Fattura Scontrino WD HD Caviar Green Videofantasy.pdf
-rw-r--r-- 1 scorp scorp  681M 23 ago 19.29 lubuntu-11.04-desktop-i386.iso
-rw-r--r-- 1 scorp scorp 1021K  1 gen  1980 Scontrino xbox 360.pdf
-rw-r--r-- 1 root  root    98M 27 ago 12.00 test2_random.dat
-rw-r--r-- 1 root  root    98M 27 ago 11.59 test_random_copy.dat
-rw-r--r-- 1 root  root    98M 27 ago 11.55 test_random.dat
-rw-r--r-- 1 root  root   293M 27 ago 12.06 test_random-with-zero-hole.dat
-rw-r--r-- 1 root  root    98M 27 ago 11.53 test_zero.dat
-rw-r--r-- 1 root  root   674M 18 ago 16.43 ubuntu-11.04-server-amd64.iso

Here I’ve copied some PDFs, 2 ISO, and some dd generated file: test_zero.dat is a dd if=/dev/zero test_random.dat and test2_random.dat are 2 different iteration with dd if=/dev/urandom test_random_copy.dat is a cp of test_random.dat test_random-with-zero-hole.dat is the result of cat test_random.dat + test_random.dat + test2_random.dat

The following are the real disk usage:

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root@debz-1:/gtank# du -sh *
259K  Fattura Garanzia redcoon dns-323.pdf
69K   fattura scontrino eeepc 900a.pdf
55K   Fattura Scontrino WD HD Caviar Green Videofantasy.pdf
675M  lubuntu-11.04-desktop-i386.iso
1,1M  Scontrino xbox 360.pdf
98M   test2_random.dat
98M   test_random_copy.dat
98M   test_random.dat
196M  test_random-with-zero-hole.dat
512   test_zero.dat
667M  ubuntu-11.04-server-amd64.iso

As you can see, compression is doing its work with ISO and test_zero.dat, but isn’t effective with PDFs and random data (do you remember that if you zip an already zip file the total size will increase?).

And what about the dedup? You should check it with:

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root@debz-1:/gtank# zpool list
NAME   SIZE  ALLOC   FREE    CAP  DEDUP  HEALTH  ALTROOT
tank  9,94G  1,60G  8,34G    16%  1.20x  ONLINE  -

so there are ~ 200 MB of available deduped space.

Other “batteries included” functions with ZFS are:

• Decrease disk I/O bottleneck using fast SSDs as caches with L2ARC
• Copy-on-write transactions: no need for fsck after hard reboot, data is always consistent on disk.
• Online Repair: ZFS store a checksum for every data block, and can notify data alternation on avery access or during a scheduled online scrub operation

Let me know if you have some good usage tips to submit!

=== START OF INFORMATION SECTION === Model Family: Seagate Barracuda 7200.11 Device Model: ST3500320AS [..] 9 Power_On_Hours 0x0032 070 070 000 Old_age Always – 26286

OH wait: 26286 / 24 / 365 = 3,00068493 yr

This disk broke exactly after 3 years. WTF?

http://blog.opennebula.org/?p=1512

I’ve bought a 13,3” Sony Vaio (VPCS13V9E), and I have found some rusty after having successfully installed Debian Squeeze.

• black screen after grub: added nomodeset kernel parameter;
• nvidia proprietary drivers not detecting screen: used custom xorg.conf, after copying /proc/acpi/video/IGPU/LCD0/EDID to /etc/EDID (not needed after nvidia-glx 260.19.44-1 from unstable);
• touchpad not working: worked after upgrading kernel 2.6.37 from unstable;
• audio not working: worked after upgrading kernel 2.6.37 from unstable;
• monitor backlight (brightness): installed nvidiabl (https://github.com/guillaumezin/nvidiabl) and created a brightness.sh (thanks to Sony BIOS that export a dummy ACPI video module) (not needed from kernel 2.6.38);
• umts modem: apt-get install gobi-loader and copy in /lib/firmware/gobi/ the blobs amss.mbn, apps.mbn, UQCN.mbn from Windoze.
• fingerprint reader (147e:1001 Upek): follow http://www.n-view.net/Appliance/fingerprint/

Section “ServerLayout”

Identifier     "X.org Configured"
Screen      0  "Screen0" 0 0
InputDevice    "Mouse0" "CorePointer"
InputDevice    "Keyboard0" "CoreKeyboard"

ModulePath   "/usr/lib/xorg/modules"
FontPath     "/usr/share/fonts/X11/misc"
FontPath     "/usr/share/fonts/X11/cyrillic"
FontPath     "/usr/share/fonts/X11/100dpi/:unscaled"
FontPath     "/usr/share/fonts/X11/75dpi/:unscaled"
FontPath     "/usr/share/fonts/X11/Type1"
FontPath     "/usr/share/fonts/X11/100dpi"
FontPath     "/usr/share/fonts/X11/75dpi"
FontPath     "/var/lib/defoma/x-ttcidfont-conf.d/dirs/TrueType"
FontPath     "built-ins"

Load  "extmod"
Load  "dbe"
Load  "glx"
Load  "dri"
Load  "dri2"
Load  "record"

Identifier  "Keyboard0"
Driver      "kbd"

Identifier  "Mouse0"
Driver      "mouse"
Option      "Protocol" "auto"
Option      "Device" "/dev/input/mice"
Option      "ZAxisMapping" "4 5 6 7"

Identifier   "Monitor0"
VendorName   "Monitor Vendor"
ModelName    "Monitor Model"

Identifier  "Card0"
Driver      "nvidia"
Option "ConnectedMonitor" "DFP-0,DFP-1,CRT-0"
Option "CustomEDID" "DFP-0: /etc/EDID"
Option  "NoLogo" "true"
VendorName  "nVidia Corporation"
BoardName   "GT218 [GeForce 310M]"
BusID       "PCI:1:0:0"

Identifier "Screen0"
Device     "Card0"
Monitor    "Monitor0"
DefaultDepth    24
SubSection "Display"
    Depth     24
EndSubSection

EndSection

/etc/acpi/nvidia_backlight_up.sh

VAL=$MAX

echo -n $VAL > /sys/class/backlight/nvidia_backlight/brightness

/etc/acpi/nvidia_backlight_down.sh

VAL=$MIN

echo -n $VAL > /sys/class/backlight/nvidia_backlight/brightness

/etc/acpi/events/sony-brightness-up event=video/brightnessup BRTUP 00000086 00000000 action=/etc/acpi/nvidia_backlight_up.sh

/etc/acpi/events/sony-brightness-down event=video/brightnessdown BRTDN 00000087 00000000 action=/etc/acpi/nvidia_backlight_down.sh

faf675e54e68daa15bc95d883166e4ce amss.mbn d7496085f1af3d1bfdf0fa60c3222766 apps.mbn 633bed88c29244683635c261849d0e88 UQCN.mbn

This is how I did it:

• Create a view that list the activity stream items published in the last week;
• Create a new content type (ex: activitystreamdigest), add a node-reference cck field with unlimited values, checkboxes as widget type and the precedent view as nodes that can be referenced;
• Update your frontpage view to include this new type of content (or promote them to frontpage, as you use to deal with your contents)

Now, everytime I want to create an Activity Stream digest, I go for Create Content –> Activity Stream Digest, I select the items I want in my digest (throwing away unuseful tweets) and publish.

You can see an example output here.

References: http://code.google.com/support/bin/answer.py?answer=62464

MiniCorso_Linux_server_GOLEM_2010

RFC2616 says:

The purpose of the 100 (Continue) status (see section 10.1.1) is to allow a client that is sending a request message with a request body to determine if the origin server is willing to accept the request (based on the request headers) before the client sends the request body. In some cases, it might either be inappropriate or highly inefficient for the client to send the body if the server will reject the message without looking at the body.

We can configure Squid to simply ignore that request header, and usually client with poor error handling will fallback without even notice it.

Add in squid.conf: ignore_expect_100 on

Android application like AppBrain and Facebook Contact Sync, and BOINC client was having login issues due to this reason.

Via @drg

An exceptional pain when using native GNU/Linux distros on Macbooks, it’s the totally awesomeness management of the fans: you could get very hot temperatures because fans will start only when thermonuclear temperatures are reached inside your machine.

Fortunately, it’s possible to manage fan speeds in userspace using the kernel module applesmc (modprobe applesmc or add it to /etc/modules), so I write a tiny bash script for doing the dirty work.

This script has been published to GitHub: http://github.com/gionn/macbook-fans

#!/bin/bash
# Settings
SMC=/sys/devices/platform/applesmc.768
TEMPMAX=90
TEMPMIN=45
FANMAX=6200
FANMIN=2000

# Thanks to god my cousin knows Math.
C1=$(( $FANMAX - $FANMIN ))
C2=$(( $TEMPMAX - $TEMPMIN ))
CF=$(( $C1 / $C2 ))
TM=$(( $CF * $TEMPMAX - $FANMAX  ))

# Be sure that manual mode is disabled:
# we don't want to burn everything is case of a bug
echo 0 > $SMC/fan1_manual
echo 0 > $SMC/fan2_manual

while :
do
CORETEMP1=$(( `cat /sys/devices/platform/coretemp.0/temp1_input` / 1000 ))
CORETEMP2=$(( `cat /sys/devices/platform/coretemp.1/temp1_input` / 1000 ))
TEMP=$(( ($CORETEMP1 + $CORETEMP2) / 2 ))
SET=$(( $CF * $TEMP - $TM ))
echo $SET > $SMC/fan1_min
echo $SET > $SMC/fan2_min
sleep 2
done

You can put this script in /usr/local/bin/fans, chmod +x /usr/local/bin/fans and add it in /etc/rc.local for automatic startup on system boot.

For Ubuntu you should use: http://old-releases.ubuntu.com/ubuntu/ For Debian you should use: http://archive.debian.org/debian/

With these mirror you should be able to deboostrap an old ancient Debian buzz (1.1) or Ubuntu Warty Warthog (4.10) :)

Questa è una versione di testing (RC1 RC3 – Changelog), ma che dovrebbe già esser abbastanza stabile per l’utilizzo di tutti i giorni. E’ uscita la release stabile CyanogenMod 6.0.0 6.1.0 basata su Android 2.2

La procedura di aggiornamento del post precedente è sempre valida (DangerSPL è obbligatorio, ma non serve reinstallarlo ogni volta).

Download: XDA