Some issue seems to be solved about installing Arch Linux on my chromebook

Try again

Since I failed twice to install Arch linux on my chromebook, I tried once again tonight.
I followed same steps of last time and installed arch on my usb and booted. (in fact in last two times I successfully installed arch linux on my usb but due to some errors occurred when running post-install.sh I thought whole installation process was completely failed)

Then I tried to run post-install.sh but same error occurred. I quit to tackle post-install.sh and switched to manually installing packages by using packman.
First, I installed Python3.4
$ pacman -S python
It was success! Now I can run python script on my chromebook!

Next I tried to install desktop environment. First I tried GNOME pacman -S gnome but failed by error. Next tried mate but also failed by error.
The error was when downloading from mirror somehow I couldn't mirror and it turned out as an error.
after I searched web I found this.
In that web page, someone said we can manually select mirror site rather than geo based selection. So I modified a file to manually pick mirror.
$ nano /etc/pacman.d/mirrorlist
I switched to a mirror located in somewhere in Canada. After that, once again I tried to install mate and .... it worked like a magic!
Installation of mate and all dependencies were successfully done. So I rebooted and it should have been completely alright.
Actually, it wasn't. When I rebooted boot process was stopped saying
[FAILED] Failed to start Light Display Manager
see 'systemctl status lightdm.service' for details
Now I got another problem to solve.
I also found that switching mirror before running post-install.sh it might work well.