Scripting in Google ChromeOS

I recently got my hands on one of those Google ChromeBooks (Cr-48). Interesting to have an operating system that is just a web browser. But, as anyone likely reading this article already knows, the graphical interface is the web browser and the operating system is still Linux. But what version? Well, let’s go on a journey together. First, you need ChromeOS. If you’ve got a ChromeBook this is a pretty easy thing to get. If not, check for a USB or optical download that can be run live (or even in a virtual machine). Or, if you know that you’re going to be using a virtual machine, consider a pre-built system from hexxeh at I have found the VMware builds to be a bit persnickety about the wireless on a Mac, whereas the VirtualBox builds ran perfectly. I split my time between the two anyway, so I’ve just (for now) been rocking VirtualBox for ChromeOS. When you load it for the first time it asks for a Google account. Provide that, select your network adapter, choose from one of the semi-lame account images ( for the record, I like the mad scientist one) and you’re off to the races. Next, we need a shell. When you first log in, you see a web page that shows you all of the Chromium apps you have installed. By default, you’ll see File manager and Web Store. If you’ve used the OS X App Store then the Chrome Web Store is going to look pretty darn familiar. My favorite for now is Chrome Sniffer. But all of these kinda’ get away from where we’re trying to go: get a scripting environment for Chrome OS. Chrome comes with 2 types of shell environments. The first is crosh. To bring up a crosh environment, use Control-Alt-t. This keystroke invokes the crosh shell. Here, type help to see a list of the commands available. Notice that cd, chmod, etc don’t work. Instead, there are a bunch of commands that a basic user environment might need for troubleshooting primarily network connections. “But this is Linux” you ask? Yup. At the help output you’ll notice shell. Type shell and then hit enter. The prompt will change from crosh> to chronos@localhost. Now you can cd and perform other basic commands to your hearts delight. But you’re probably going to need to elevate privileges for the remainder of this exersize. So let’s type sudo bash and just get there for now. If you’re using a ChromeBook, the root password might be root, or if you’re using a downloaded vm from hexxeh then it might be facepunch (great password, btw). Provided the password worked, the prompt should turn red. Now, if you’re using a hexxeh build then the file system is going to be read-only. You won’t be able to change the root password nor build scripts. But otherwise, you should be able to use passwd to change the password: passwd chronos Once you’ve got slightly more secure shell environment (by virtue of not using the default root password), it is time to do a little exploring. Notice that in /bin, you see sh, bash, rbash and the standard fare of Linux commands (chmod, chown, cp, attr, etc. Notice that you don’t see tcsh, csh or ksh. So bash commands from other platforms can come in, but YMMV with tcsh, etc. Running ps will give you some idea of what’s going on process-wise under the hood: ps aux From encrypts to crypto to the wpa supplicant, there’s plenty to get lost in exploring here, but as the title of the article suggests, we’re here to write a script. And where better to start than hello world. So let’s mkdir a /scripts directory: mkdir /scripts Then let’s touch a script in there called touch /scripts/ Then let’s give it the classic echo by opening it in a text editor (use vi as nano and pico aren’t there) and typing: echo "Hello Cruel World" Now close, save and then run it: /scripts/ And you’ve done it. Use the exit command twice to get back to crosh and another time to close the command line screen. You now have a script running on ChromeOS. Next up, it’s time to start looking at deployment. This starts with knowing what you’re looking at. To see the kernel version: uname -r Or better: cat /proc/version Google has been kind enough to build in similar sandboxing to that in Mac OS X, but the concept that you can’t run local applications is a bit mistaken. Sure, the user interface is a web browser, but under the hood you can still do much of what most deployment engineers will need to do. If these devices are to be deployed en masse at companies and schools, scripts that setup users, bind to LDAP (GCC isn’t built-in, so it might be a bit of a pain to get there), join networks and the such will need to be forthcoming. These don’t often come from the vendor of an operating system, but from the community that ends up supporting and owning the support. While the LDAP functionality could come from Google Apps accounts that are integrated with LDAP, the ability to have a “One touch deploy” is a necessity for any OS at scale, and until I start digging around for a few specific commands/frameworks and doing some deployment scripts to use them, right now I’m at about a 6 touch deploy… But all in good time!

Touching Date Changes

No, I’m not getting all teary-eyed about something…  Instead I’m thinking about changing the modification date stamp on a file.  Let’s take a fairly innocuous and hidden file, such as the the COOKIES file located in the /usr/share/emacs/22.1/etc directory.  Since I’ve already tried the recipe, I’m going to go ahead and replace the contents of this file with the contents of the mutex script posted a few days ago. This leaves the date the file was created altered as can be seen by doing an ls -al on the file:
-rw-r–r– 1 root wheel 4968 Apr 21 22:04 /usr/share/emacs/22.1/etc/COOKIES
We’re going to go a step further and use stat on the file to see even more information:
234881030 90192 -rw-r–r– 1 root wheel 0 4968 “Apr 21 22:04:01 2009” “Apr 21 22:04:01 2009” “Apr 21 22:04:01 2009” “May 15 16:57:33 2007” 4096 16 0 /usr/share/emacs/22.1/etc/COOKIES
The following command will set the modified date to the same as the creation date (the last of the dates listed:
touch -t 200705151657 /usr/share/emacs/22.1/etc/COOKIES
There are more than likely going to be times when you don’t want to update a file but instead replace it. For example, if we removed COOKIES and then did a curl of a file to /usr/share/emacs/22.1/etc/COOKIES then the Linux version of touch would typically have a -d option, for that pesky creation date, but as the Mac OS X binary nastygrams that it’s an illegal option, we’re going to use the SetFile command. Below, we’ll take whatever file that has been dropped into the appropriate location and then set a new creation time for the file, to match that of the original file:
./SetFile -d “5/15/2007 57:33” /usr/share/emacs/22.1/etc/COOKIES

Mac OS X: Running Non-Server OSen on VMware

Beware: if you proceed with this you will violate the EULA of Mac OS X. In fact, reading this article may very well violate said EULA. In fact, reading this warning may… Catch my drift? So Mac OS X is not supported in VMware beta 2. Well, like many things that doesn’t mean that you can’t make it work. To get Mac OS X (not Mac OS X Server) to install into a VMware Fusion beta 2 VM use the following command, create an ISO with the name Mac OS X Install DVD that is a duplicate of the installer DVD and mount it: touch “/Volumes/Mac OS X Install DVD/System/Library/CoreServices/ServerVersion.plist” This will create the file that VMware looks for to determine whether you can run Mac OS X in a VM. You can rm it from /Volumes/Macintosh HD/System/Library/CoreServices/ServerVersion.plist once you are finished with the installer, but might want to keep it handy as you occasionally may need it again for certain operations.