Lightweight operating system image that downloads an arbritary shell script from a HTTP or NFS server, and executes it.
To tell the image to download the script from the HTTP server with IP-address 1.2.3.4 put in cmdline.txt:
script=http://1.2.3.4/name-of-script.sh
To tell the image to download the script from the NFS server with IP-addresses 1.2.3.4 use:
script=1.2.3.4:/name-of-nfs-share/name-of-script.sh
If using NFS the script has access to other files inside the same NFS share as well. The current working directory is set to where the share is mounted before the script is executed.
Building and customizing scriptexecutor
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Within buildroot, run make busybox-menuconfig and enable gzip support for tar under the Archival Utilities menu.
There are two types of images for the Korg SparkPi line of products, a normal update image and an "update from USB Boot mode" image.
In both updater modes, the update process occurs by rewriting the /boot/config.txt file to reference an updater kernel and associated scriptexecute.img file, which contains the rootfs for the updater kernel to use during the update. When the system reboots into the updater kerner, the first thing the S99 updater will do is to rewrite the /boot/config.txt file so that the system reboots normally into the regular kernel and rootfs of the target system. It will then proceed to run any pre/post tar scripts and untar the update content to the target based on the location specified (which will vary depending on whether it is a normal update or USB boot mode update).
Each mode for a release will be located within its own branch in the repo.
Take care to that when switching between building each of the two types of images that the cached files under the output folder of the buildroot build are removed, if necessary. It is important to check the contents of the generated rootfs to make sure that no cached files from a previous type of build have been inadvertently leftover. In order to read the contents of scriptexecute.img, you can do the following:
1. Start in a folder containing a copy of scriptexecute.img file.
2. rename scriptexecute.img to scriptexecute.img.gz
3. gunzip scriptexecute.img.gz
4. Create a folder to receive the contents of the rootfs image - e.g. mkdir ./rootfs
5. Change to that folder (cd ./rootfs)
6. execute the following command:
cpio -idv < ../scriptexecute.img
In this case, the S99 script under scriptexecute/board/overlay/etc/init.d will point to an update tarball that will have been downloaded to the target system under /Korg/Updater and the path to the update will be contained in a file located at /Updater/CurrentInstallSourcePath on the target system.
In this special case, the same update content that would normally be in the location specified by /Updater/CurrentInstallSourcePath on the target system is instead located in the scriptexecute.img rootfs itself under the /etc/updatecontent folder. The S99 /etc/init.d script for the updater kernel's rootfs is modified to use this hardcoded location and the update proceeds as it would in the normal case.
An important note here is that the USB Boot Mode update's content MUST also contain the normal mode update kernel and image that resides under /boot so that the updater kernel and scriptexecute.img that was installed specifically for the USB Boot mode update will get replaced back to the normal ones so that any subsequent normal mode update will continue to work.