Read only target file system: Difference between revisions
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Revision as of 17:44, 28 February 2014
Overview
Typically the root file system, also called the target file system from an SDK perspective, contains the device's applications and libraries. These should not be modified during normal device operation. The simpliest way to ensure the files are not changed is to mount the entire root file system read-only.
The challange is some common files, like /etc/network/interfaces gets modified. To allow for the handful of standard POSIX configuration files to be modified, symbolic links are used. the actual file reside in a separate file system that is mounted read / write.
SDK configuration
To configure your target file system to be mounted read-only, run the SDK configuration tool and select:
- File System Configuration ---> Create read only target file system
SDK read-only target file system creation process
The target file system is created as normal, with two changes:
- After the target file system is created, the contents of $DEVDIR/fs/overlay-ro are overlaid on the target file ssytem. The contents of the overlay-ro directory is typically symbolic links for the files whose contents can change.