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Accepted
Jasmine Lognnes
Asked: 2016-04-16 04:23:26 +0800 CST

How to avoid loosing changes on the root filesystem when kernel upgrading?

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On Solaris and variants, it makes a zfs clone of the current / filesystem and installs the new kernel there. When rebooting you get the new /.

In my case I have a /scripts directory, so if I ever should go back to a previous kernel, then my /scripts would also get rolled back, which to me should be independent of with kernel I am on.

Question

How can I avoid loosing the changes made to the filesystem from the time the kernel upgrade is finished till the host is rebooted?

Is there a procedure I am not aware of, as even if you are very fast to reboot after the kernel upgrade, log entries could easily have been made, which you would never see.

solaris filesystems zfs omnios

1 Answers

  1. Best Answer

    What you described are Boot Environments (BE), which will be created automatically on system upgrades or manually with the beadm command.

    You can have multiple independent BEs, although only a single one can be active at the same time. You also can update/modify each BE separately. Normally you would do that to test specific software versions or a full system upgrade, but it is not restricted to that.

    From Advantages to Maintaining Multiple Boot Environments:

    Although only one boot environment can be active at a time, you can mount an inactive boot environment by using the beadm mount command. Then, you could use the pkg command with the alternate root (-R) option to install or update specific packages on that environment.

    I just tried it, beadm mount BeName will mount BeName in a temp directory under /tmp, which is writeable. You could write a simple script to sync/copy your new or changed files to the old BE or vice versa.

    The documentation also states that snapshots on BEs are possible (with beadm create BeName@snapshotNamedescription), which may be helpful if you want to track differences that occurred between two points in time (with zfs diff).

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