What the importance of a mirror copy on the same SD card?

torontob

Hi Everyone,

I use embedded Alix boards and I have noticed that the nanoBSD image that loads onto the Flash card create two partitions and I think they are exact mirror of each other. What is the importance of this? Is it to do the factory default or is this some sort of redundancy measure? If it is, how can it be best utilized?

Thanks

Efonnes

As far as I know, it is mainly a backup in case of a failed upgrade or any other reason you might end up with a corrupt OS.

torontob

Thanks for the feedback.

1- I want to know how the backup can be triggered? Would OS boot automatically fall to the second partition if the first fails?
2- Would it be by simply choosing option 2 at boot time?
3- What is the way to set the mirror as the default at start-up?
4- Are the configurations copied between the two mirrors as a system is built? If not, really this other partition is useless and waste of space isn't it? Since, it's probably much more cleaner and might take the same time to re-image the whole thing anyhow.

Thanks,

wallabybob

@torontob:

it's probably much more cleaner and might take the same time to re-image the whole thing anyhow.

Not if the box has to be opened to remove the flash card so it can be re-imaged.

cmb

@torontob:

1- I want to know how the backup can be triggered? Would OS boot automatically fall to the second partition if the first fails?
2- Would it be by simply choosing option 2 at boot time?
3- What is the way to set the mirror as the default at start-up?
4- Are the configurations copied between the two mirrors as a system is built? If not, really this other partition is useless and waste of space isn't it? Since, it's probably much more cleaner and might take the same time to re-image the whole thing anyhow.

you have to choose it at boot time.
yes
Diag>Nanobsd
there is one shared config partition.

It's primarily if you want to upgrade one and have the option to revert back to the previous version. (with caveats for drastically different versions, like 1.2.3 vs. 2.0, where the configs aren't compatible)