Torizon, changes to /opt folder

Technical Support
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1

Hi,

I can use the “changes” folder to modify the filesystem as follows:
Build PC | Target
changes/usr/bin → /bin
changes/usr/lib → /lib
changes/usr/etc → /etc

However, I cannot modify the /opt folder on the target:
changes/usr/opt → /usr/opt # Incorrect, need /opt
changes/opt → # Build error
changes/var/rootdirs/opt → # Data not present

How would I go about sorting this out?

Lloyd

2

Greetings @lblackbeard,

TorizonCore and TorizonCore Builder use OSTree in order to capture and version control changes to the filesystem. The /opt directory on the device is actually symlinked like so:

ls -l /opt
lrwxrwxrwx 2 root root 16 Oct 19 18:50 /opt -> var/rootdirs/opt

This is important because the entire /var directory is not controlled by OSTree. This is by design for the purpose of having a persistent directory that is not touched. That said this means you can’t customize /opt. You would need to use another directory where changes are captured. What kind of changes were you going to use /opt for?

Best Regards,
Jeremias

3

Thanks Jeremias. That’s good info to have regarding /var not being controlled by OSTree. I am simply wanting to preinstall a driver that wants to put some files over there. I have since discovered that the path to those files can be changed in a configuration file, so things are working now as they should. I am slightly concerned though that the approach is mildly contortionist and relies on the driver respecting its own configuration.
While I have you, why is /etc not a link to /usr/etc in the same way as /bin and /lib?
Lloyd

4

While I have you, why is /etc not a link to /usr/etc in the same way as /bin and /lib?

Well the answer to this again is OSTree. The /etc directory is another kind of special directory in the OSTree framework. So this directory is tracked and versioned by OSTree, but in a somewhat unintuitive way.

Basically when an update/upgrade with OSTree occurs, a 3 way merge happens to the /etc directory. The merge is between the current state (/etc), the default state (/usr/etc), and the new state ( the new /usr/etc). This document describes the process in more detail: Atomic Upgrades | ostreedev/ostree

But basically, that’s why /etc is not just a simple symlink of /usr/etc. /usr/etc is just a copy of the default state of /etc, but not necessarily equal to the current state of /etc.

I hope that helps clear that up.

Best Regards,
Jeremias

1 Like
5

Can we add new libraries directly in torizoncore if we copied a .so file to the usr/lib folder?

6

Hi @SJ_BHD !

By default, /usr and /lib are read-only folders.

Directly changing these folders is not recommended.

You could use TorizonCore Builder’s build command to add files to customize your TorizonCore (please check the Example: Simple Customization section of TorizonCore Builder Tool “build” command | Toradex Developer Center).

But if you need those shared objects (.so files) for your application, it is recommended to have those files in the application’s container.

Best regards,

7

If you’re after adding a library at runtime and it absolutely has to be outside your application container(s), it’s probably easiest just to put the library somewhere in etc and add it to ld.so.conf.d.

8

Hello @SJ_BHD ,
Were you able to solve your issue with the info provided by @lblackbeard ?

Best regards,
Josep

9

Thanks. The response from @henrique.tx has resolved my issue.