My words on free/open source software

Saturday, December 25, 2010

Easy way to align Linux partitions for SSD and myths debunked

Recently I got a laptop from my employer with an Intel X25-M SSD drive in it. I have spent some time trying to figure out the best and easiest way to install Linux onto it while retaining the Windows 7 (so I have to use MBR instead of GPT). There are numerous discussions you can find on the net, some of them are quite complex and some are simply misleading (if not wrong). In fact this task is quite easy with modern Linux and here's a documentation of what I've done. This blog is not meant to be a full discussion on this topic, but only intended as a cheat sheet for those experienced Linux users (if you want a more detailed and correct discussion on this topic, I recommend Ted Ts'o's blog: Aligning filesystems to an SSD’s erase block size.)

For those impatient readers, here's an overview: the disk geometry (or C-H-S value) you see from partition programs as well as the warning about partitions are not aligned to cylinder boundary don't matter at all so there's no point to spend time on tuning loose knobs. New GParted (I used 0.7.1 from SysRescueCD, not to be confused with "GNU parted") is a very easy to use tool and it now defaults to create partitions aligned on 1 MiB (I heard that Ubuntu 10.10 and later can do partition alignment automatically too but I haven't tried that).

Here's the detail:

The myth: Does the C-H-S value still matter?

A lot of discussions were about checking the disk geometry after partitioning. However, in fact no modern operating system pays attention to those values any more (see the comment by Ted Ts'o). And those "-H xx -S xx" options passed to fdisk are only meant to make that fdisk program happy so it can create partitions aligned with cylinder boundaries. Although the C-H-S values are stored in MBR, they are not used by the Linux kernel who runs the whole system. Instead of paying attention to choosing or checking those C-H-S values, you should only need to make sure that the start and end sectors of partitions are multiples of the size of your erase block. Of course you can use any good partition programs to do this.

So you don't have to use that fdisk program

and you can simply choose any program that you are familiar with. For me I'm comfortable with sfdisk and GParted. This time I tried latest GParted and was very happy to see it had supported partition alignment on 1 MiB boundary. So my work is done in one minute without using a calculator. After that I also carefully checked the partition table with "sfdisk -uM" and was sure that those partitions were aligned on MiB boundaries. The extended partition was not aligned but I thought that didn't matter as long as all logical partitions in it were aligned correctly.

A few more tips:

  • If you want to have TRIM/DISCARD support you can use a 2.6.33+ kernel with Ext4 file-system, mounted with -o discard.

  • When making the Ext4 file-system, make sure you use the stripe-width option and let it align with erase block boundary too (see Ted's post above).

  • Don't use LVM or dm-crypt since they don't support TRIM/DISCARD command yet. Newer kernel supports TRIM/DISCARD passing along in LVM and dm-crypt.

compilebench test result:

Intel's X25-M is very smart that even if you don't align the access correctly the drive will do magic under the hood so the initial benchmark data doesn't differ too much, however, the performance will degrade much more quickly as the internal mapping tables getting more and more complex due to unaligned writes. Here I post the file-system benchmark result when it's still new. I'll try to do benchmark again after several months to see if there's any performance degrade (although my usage is not heavy).

I used compilebench v0.6 because I think it mimics daily desktop usage very well.

Machine spec:
System: Debian Squeeze (testing)
Kernel: 2.6.37-rc5-amd64 from Debian experimental repo
Test command: sudo ./compilebench -D t -i 10 --makej (the same option used by Phoronix Test Suite)
File system: Ext4, mount option: rw,noatime,discard

compilebench Initial Create test result: 105.24 MB/s (on 2010-12-27).

Monday, December 20, 2010

MeeGo: Auto-Start an Application on Session Start

For modern Linux desktop, it's a common way to auto-start an application in a user-session by placing a ".desktop" file into /etc/xdg/autostart. But if you are writing or porting an application to MeeGo and found that the application is not auto-started after you put in a seemingly correct .desktop, please check this:

If there's an "OnlyShowIn=" item, it must contain the string X-MOBLIN-NB. For example:


Another caveat is that MeeGo's uxlaunch doesn't honor AutostartCondition key yet, for the sake of simplicity and fast-boot.

For code under the hood, check MeeGo's uxlaunch/desktop.c.

Saturday, December 18, 2010

Very hard to make bootable USB drive from Ubuntu 10.10's CD Image

I was spoiled by MeeGo's super convenient USB live image so I was very surprised when I found that it was very hard to make a bootable USB drive from Ubuntu 10.10's CD-ROM image for my wife.

On Linux, Ubuntu only officially supports making bootable USB drive from its CD-ROM image by using "ubuntu-usb-creator", which is not available in any Linux installations I'm using now (MeeGo, Debian, CentOS). Ubuntu's official help document mentions one alternative way -- to download a small image and combine it with the iso file -- doesn't work, and community posts pointed out that that methods only worked with "alternative iso" (not desktop iso).

Finally I found a way (and the only way) to make a usable USB drive for installation is from this post.

So what? I think Canonical really should release official USB images since most netbooks shipped today have no CD-ROM drive.

Wednesday, July 14, 2010

Google Chrome (Chromium) Sync Server Address

If you want to know the host name and address of the sync server Google Chrome (or Chromium) uses, see here:

For now, the sync service's URL is

Sunday, June 27, 2010

HOWTO: Run Plants vs Zombies™ in Linux under Wine (includes how to Register!)

I have to admit that I found PopCap's Plants vs Zombies™ (referred to as PvZ below) interesting. It runs on Windows, Mac and iPhone but not on any Linux yet.

You can download the trial version from the official site above, and it runs amazingly well on a recent Wine, without any special configuration. Well done, Winehq!

Now comes the problem, if you decide to buy it after 60 minutes play, the registration process is a bit hard with Wine. The reason is that PvZ requires an Internet Explorer or Firefox to finish the registration process. Obviously it has to gather some local hardware/system information and upload it to their activation server so that they can know how many machines you are running PvZ on, therefore you won't to able to give away free copies of the game to all your friends. I think this whole thing is OK, though instead of writing codes in PvZ to let it communicate with their server, instead, sadly, they choose to use ActiveX running in IE for this.

Some early posts reported that the registration process can be finished if you install an IE into the same Wine directory. Running IE on Wine is not impossible but hard, especially when IE4Linux project is no longer maintained.


Now I have found that you can also finished the registration process using not IE but Firefox instead. Thanks for their being in the same free software camp, Firefox runs very well on Wine. Just grab a Windows copy and install it into the same Wine directory.

Then run Firefox in your Wine, go to PopCap's Registration Page, follow the instruction there to download and install the Firefox plugin. After that, close your Firefox (for some unknown reasons, the Firefox Wine process may still linger in the background after its window is closed, run "ps -ef | grep -i firefox" and kills the linger process if need).

Now starts PvZ by running its in your winefile. Because the PvZ and Firefox need to be started in a same Wine instance so they collect the identical hardware/system information. Register it following the normal process. It may fail at the first attempt to start a web browser, keep clicking the "Retry" button until it shows it's waiting for the registration process to finish (it's waiting for web browser plugin to return registration key). Start a Firefox instance from that same winefile program. Go to PopCap's Registration Page, now if your plugin is installed successfully, it should show a web page asking for your POP Order Number, give it and the registration process should finish successfully and the PvZ program should proceed to the game.

It's not rocket science, just nuisance.

PvZ runs very well in Wine during my 2 days play. I can say it's perfectly running on Linux for now.

Known Problems

  1. Sound effects may not work on some machines with some old Wine versions (try upgrade to latest Wine.)

  2. The full-screen mode will be always "full-screen," which means that if you have a non-4:3 screen, it will be slightly torted.

  3. The between-battle preview screen may be a bit slow sometimes, but as soon as the battle begins the speed returns to normal (not sure if it shows similar issue when running on a real Windows.)

Saturday, June 26, 2010

Running Wine on MeeGo

One of the good thing of MeeGo is that it contains a standard X server along with full 2D/3D acceleration. Having a full X stack running on your netbook enables the possibility to use a good variety of exist fun Linux programs. Such as Wine.

In order to play Plants vs Zombies™ and Zuma™, I have installed Wine on MeeGo. Wine is not in MeeGo's official repo (yet), so I just downloaded all wine-*.rpm from Fedora's rawhide repo and the installation was a breeze. I hope MeeGo will have it's own Wine package soon, it should be quite easy to repackage with minor tweaks from Fedora's packaged Wine. Thanks Fedora project! Anyone in the community want to volunteer?

Sunday, May 02, 2010

HOWTO: Disable IPv6 in MeeGo

With traditional desktop Linux distros, the IPv6 can be disabled by removing the ipv6-related modules, but not with MeeGo since it's ipv6 module is compiled in kernel (for fastboot). The following instructions apply to similar situations where you can't remove the ipv6 module (like you have no control over the kernel, or using a Xen VM, etc.)

The ipv6 module will always assign an address to all NIC during startup, there's no way to disable it, we have to disable ipv6 autoconf, and remove all assigned IPv6 addresses:

Create a file /etc/sysctl.d/disable_ipv6:

# disable autoconf

# block all received Router-Advertisement (RA) packets
net.ipv6.conf.default.accept_ra = 0
net.ipv6.conf.all.accept_ra = 0
net.ipv6.conf.eth0.accept_ra = 0

# NOTE: the *.all* above applies to newly created NICs only,
# not to existing NICs. So you have to list all NIC's explicitly
# here. For example, if you have a wireless card wlan0, add the
# following lines:
#net.ipv6.conf.wlan0.accept_ra = 0

Then delete all pre-allocated ipv6 address by adding the following lines in /etc/rc.local:

ifconfig lo inet6 del ::1/128
IPV6ADD=`ifconfig eth0 | grep inet6 | awk '{print $3}'`
ifconfig eth0 inet6 del "$IPV6ADD"

Don't forget to:

chmod +x /etc/rc.local

I've discovered that sshd running on MeeGo can't accept X11 forwarding requests after made above changes. You can find the following error message in /var/log/secure:

sshd[]: error: Failed to allocate internet-domain X11 display socket.

The reason is that sshd is still trying to bind to an IPv6 address but there's no IPv6 address available. To solve this issue, we need to start sshd with "-4" option.

Create a new file For MeeGo at /etc/sysconfig/sshd:


And restart sshd:

service sshd restart


Sunday, March 28, 2010

MeeGo is in Google Summer of Code 2010

MeeGo has joined Google Summer of Code 2010. If you are a student, have some free time this summer and have interests in developing operating system or applications for new small form factor devices, please consider join us!

MeeGo is the combined Moblin and Maemo and is sponsored by Linux Foundation, Nokia and Intel. To make it simple, MeeGo is the new operating system, inspired by the rising interests and challenge in smart phone and mobile internet devices, for future Intel and Nokia ARM platforms (or more if other handset makers join).

To distinguish it from other smart phone platforms such as iPhone and Android, MeeGo is proudly bearing the badge "open." It is not controlled by a single authority, but under the non-profit consortium Linux Foundation and welcome all parties and individuals who interests in making the best mobile platform in the world.

Another thing that distinguishes MeeGo from other mobile platforms is that MeeGo runs full Linux desktop stack. It is running unmodified Linux kernel, X server, compiled by unmodified GCC, includes full GTK / GNOME and Qt libraries. So all your expertise on desktop Linux continues to thrive here.

But MeeGo is not yet-another-Linux-distro. Smart minds may already spot the great challenge here. How could we build a competing platform by using just commodity GNU/Linux OS codes? The answer from us is that we are focusing on usability plus aggressive optimization. We believe the codes from those great upstream free software community is the best in the world and we can build the solid state-of-art platform based on them. What we have to do is try our best to integrate them together and focus on design a great user experience.

So if you are interested, please take a look at the MeeGo project ideas. Of course we are more than happy if you can come up with you own great ideas. And try to get yourself a $5,000 stipend.

(all words above are my personal opinion and reflect no idea from MeeGo committee, Linux Foundation, Nokia or Intel)

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Santa Cruz, California, United States