Deployment Chroot

When Trident is deploying a target OS, it will mount the target OS's file systems and prepare them for a chroot. This mount of the target OS is called newroot.

chroot is a Unix operation that changes the apparent root directory for the current running process and its children. A program that is run in such a modified environment cannot access files outside the designated directory tree.

Trident will then chroot into the newroot and run commands in the context of the target OS. This allows Trident to perform tasks such as installing the boot loader, configuring the network, and other tasks that require running commands in the context of the target OS.

Trident uses chroot to change the root directory of the current process to the newroot. This means that any commands run after the chroot command will be executed in the context of the target OS.

When Trident is running in the newroot, it will have access to the file systems of the target OS, but it will not have access to the file systems of the servicing OS.

Trident will also mount certain directories from the servicing OS into the newroot to ensure that necessary files and directories are available in the context of the target OS. These directories include /proc, /sys, /dev, and /run.

This is particularly relevant for any postConfigure scripts defined in the Host Configuration. These scripts are run from within the chroot of the target OS, with the $TARGET_ROOT variable set to /.

warning

The postConfigure scripts are run within a chroot environment, which while it is kind of similar to containers, is very explicitly not a sandbox environment. So, such scripts have the ability to modify the servicing OS.

In particular, you should be very wary of commands that have the ability to change the runtime kernel settings. And even commands that only read runtime kernel settings are probably doing the wrong thing, since the servicing OS's kernel is likely entirely unrelated to the customized OS’s kernel.

Instead, you should make use of config files that set the target OS's runtime kernel settings during OS boot.

Once Trident has completed its tasks in the context of the target OS, it will exit the chroot and unmount the newroot and any mounts that were created.