Difference between revisions of "OpenBSD readonly root"
(New page: = Theory = In a lot of situations, you'll find yourself not wanting to check filesystems, thereby<br /> facilitating hard power-downs with ~no data loss. I've come across this case a few...) |
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mostly in the end-user or volatile-power routing environments. Most often, I've done this<br /> | mostly in the end-user or volatile-power routing environments. Most often, I've done this<br /> | ||
on [http://www.soekris.com/ Soekris] [http://www.soekris.com/net4801.htm net4801] devices.<br /> | on [http://www.soekris.com/ Soekris] [http://www.soekris.com/net4801.htm net4801] devices.<br /> | ||
| + | We'll show an example of how to do it on a net4801, which is the same procedure for a net5501,<br/> | ||
| + | and we'll be using OpenBSD 4.6 for the example.<br/> | ||
<br /> | <br /> | ||
To perform such a magic trick, you need to do a bit more planning. It's not as easy to run some<br /> | To perform such a magic trick, you need to do a bit more planning. It's not as easy to run some<br /> | ||
| Line 15: | Line 17: | ||
= Practice = | = Practice = | ||
| − | + | == Installation == | |
| + | Perform a PXE-boot standard OpenBSD 4.6 i386 install, the following differences apply:<br/> | ||
| + | * Press ^P at the 5-second BIOS countdown, then "boot f0" to boot from the first ethernet port. | ||
| + | * Interrupt the loader after it gives you a prompt (type anything, it stops the counter). | ||
| + | * Type the following, in this order: | ||
| + | |||
| + | stty com0 19200 | ||
| + | set tty com0 | ||
| + | boot /bsd.rd | ||
| + | |||
| + | You should now be booting a kernel and be tossed into the OpenBSD installer.. look elsewhere<br/> | ||
| + | for instructions on how to properly setup PXE booting for OpenBSD, or maybe I'll document it<br/> | ||
| + | someday.<br/> | ||
| + | <br/> | ||
| + | * When installing, you should partition your CF card with 1 giant / partition, and *no swap* | ||
| + | * It'll ask you later on if you want to change the console to com0, tell it yes and choose 19200 to match the soekris BIOS settings.<br/> | ||
| + | * Once installed, reboot into your installation and do basic post-install configuration, including setting up network interfaces, adding packages, configuring sudo, etc.. the idea is to have a fully installed system that just needs configuration. | ||
| + | <br/> | ||
| + | Login and 'sudo ksh' if you haven't already: you'll need to perform a number of steps,<br/> | ||
| + | which I'll detail below.. another time ;) | ||
Revision as of 13:42, 3 December 2009
Theory
In a lot of situations, you'll find yourself not wanting to check filesystems, thereby
facilitating hard power-downs with ~no data loss. I've come across this case a few times,
mostly in the end-user or volatile-power routing environments. Most often, I've done this
on Soekris net4801 devices.
We'll show an example of how to do it on a net4801, which is the same procedure for a net5501,
and we'll be using OpenBSD 4.6 for the example.
To perform such a magic trick, you need to do a bit more planning. It's not as easy to run some
services in a configuration like this, since they need areas to write to. Even worse is when they
need to write data that you actually want to keep. In this case, I like to avoid the RO root
scenario, because it adds some awkward complexity that involves a regular mount-writable/sync/remount-ro
cycle. In general though, most services you can get away with just providing them ramdisk scratch
space.
Practice
Installation
Perform a PXE-boot standard OpenBSD 4.6 i386 install, the following differences apply:
- Press ^P at the 5-second BIOS countdown, then "boot f0" to boot from the first ethernet port.
- Interrupt the loader after it gives you a prompt (type anything, it stops the counter).
- Type the following, in this order:
stty com0 19200 set tty com0 boot /bsd.rd
You should now be booting a kernel and be tossed into the OpenBSD installer.. look elsewhere
for instructions on how to properly setup PXE booting for OpenBSD, or maybe I'll document it
someday.
- When installing, you should partition your CF card with 1 giant / partition, and *no swap*
- It'll ask you later on if you want to change the console to com0, tell it yes and choose 19200 to match the soekris BIOS settings.
- Once installed, reboot into your installation and do basic post-install configuration, including setting up network interfaces, adding packages, configuring sudo, etc.. the idea is to have a fully installed system that just needs configuration.
Login and 'sudo ksh' if you haven't already: you'll need to perform a number of steps,
which I'll detail below.. another time ;)