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Old 02-21-2012, 07:45 AM
Alex Walker
 
Default Ways To Practice Breaking My System?

Hi All

I've been looking into some ways to break a CentOS system so I can
perform some simulated disaster recovery and get some hands-on practice
with rescue mode and other system recovery tools. I'm thinking to start
off with things like corrupting the password file with random
characters, breaking grub.conf.

I've been doing some research on the net, but would welcome any input
from list members. Does anybody have any creative suggestions for ways
to break the CentOS boot process?

Thanks in advance


Alex.
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Old 02-21-2012, 09:14 AM
David
 
Default Ways To Practice Breaking My System?

On 21/02/2012, Alex Walker <tech@alexwalker.org.uk> wrote:
> Does anybody have any creative suggestions for ways
> to break the CentOS boot process?

I have *not* actually tried it myself, but this might help you:
http://trouble-maker.sourceforge.net/
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Old 02-21-2012, 11:39 AM
Alex Walker
 
Default Ways To Practice Breaking My System?

On 21/02/2012 10:14, David wrote:
> On 21/02/2012, Alex Walker<tech@alexwalker.org.uk> wrote:
>> Does anybody have any creative suggestions for ways
>> to break the CentOS boot process?
> I have *not* actually tried it myself, but this might help you:
> http://trouble-maker.sourceforge.net/
> _______________________________________________
Thanks, that looks to be a good start, will give it a try


Alex.
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Old 02-21-2012, 11:57 AM
Boris Epstein
 
Default Ways To Practice Breaking My System?

On Tue, Feb 21, 2012 at 3:45 AM, Alex Walker <tech@alexwalker.org.uk> wrote:

> Hi All
>
> I've been looking into some ways to break a CentOS system so I can
> perform some simulated disaster recovery and get some hands-on practice
> with rescue mode and other system recovery tools. I'm thinking to start
> off with things like corrupting the password file with random
> characters, breaking grub.conf.
>
> I've been doing some research on the net, but would welcome any input
> from list members. Does anybody have any creative suggestions for ways
> to break the CentOS boot process?
>
> Thanks in advance
>
>
> Alex.
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos


Things like boot process rarely break. Try something like filling up your
root or tmp partition. That just seems to be a bit more common as far as
problem scenarios go.

Good luck

Boris.
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Old 02-21-2012, 12:33 PM
Les Mikesell
 
Default Ways To Practice Breaking My System?

On Tue, Feb 21, 2012 at 2:45 AM, Alex Walker <tech@alexwalker.org.uk> wrote:

> Hi All
>
> I've been looking into some ways to break a CentOS system so I can
> perform some simulated disaster recovery and get some hands-on practice
> with rescue mode and other system recovery tools. I'm thinking to start
> off with things like corrupting the password file with random
> characters, breaking grub.conf.
>
> I've been doing some research on the net, but would welcome any input
> from list members. Does anybody have any creative suggestions for ways
> to break the CentOS boot process?
>
>
If you want a real workout, try restoring your backups on a different
machine - where more hardware differences or raid layout changes can make
it harder. It is also a realistic thing to need to do. Grub isn't nearly
as likely to fail as a disk drive, motherboard, or power supply.

--
Les Mikesell
lesmikesell@gmail.com
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Old 02-21-2012, 02:00 PM
Warren Young
 
Default Ways To Practice Breaking My System?

On 2/21/2012 5:57 AM, Boris Epstein wrote:
> Things like boot process rarely break.

I can't remember the last time I caused a system to outright fail to
boot, but I *do* get unclean boots regularly.

Examples:

- Build and install some needed driver from source, yum upgrade
repeatedly, implicitly upgrade kernel, forget to rebuild the driver
against the new kernel, reboot, boom.

- Get asked to configure the foo service, get it all working, forget to
add it to init.d, use it happily for months, reboot, fail to notice the
service's absence until someone gives a misleading bug report. ("The
foo service has crashed!") Then I have to go chasing it, handicapped by
being half a year separated from the last time I looked at it.

What with the long uptimes on our servers and their many-hattedness, I'd
say chances are actually fairly low that any given reboot will bring it
100% back to the state it was in when we shut it down. Something
boot-related almost *always* changes between reboots.

I've made it a policy that if you get an unclean reboot, you fix it in
such a way that it should come up cleanly, then test by rebooting.
Repeat until all symptoms are fixed. But, never believe you've thereby
guaranteed that it will come up cleanly the next time.
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Old 02-21-2012, 02:03 PM
"D. Marshall Lemcoe Jr."
 
Default Ways To Practice Breaking My System?

Pull out one of the hard drives while it's still running and see if
RAID keeps up. For more fun, see how the latencies increase!

On Tue, Feb 21, 2012 at 3:45 AM, Alex Walker <tech@alexwalker.org.uk> wrote:
> Hi All
>
> I've been looking into some ways to break a CentOS system so I can
> perform some simulated disaster recovery and get some hands-on practice
> with rescue mode and other system recovery tools. I'm thinking to start
> off with things like corrupting the password file with random
> characters, breaking grub.conf.
>
> I've been doing some research on the net, but would welcome any input
> from list members. Does anybody have any creative suggestions for ways
> to break the CentOS boot process?
>
> Thanks in advance
>
>
> Alex.
> _______________________________________________
> CentOS mailing list
> CentOS@centos.org
> http://lists.centos.org/mailman/listinfo/centos
_______________________________________________
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http://lists.centos.org/mailman/listinfo/centos
 
Old 02-21-2012, 02:05 PM
Warren Young
 
Default Ways To Practice Breaking My System?

On 2/21/2012 1:45 AM, Alex Walker wrote:
>
> I've been looking into some ways to break a CentOS system so I can
> perform some simulated disaster recovery

Bring up a fresh CentOS 6.0 system. Disable automatic updates. Add a
bunch of third-party software. Install at least one bit of hardware so
nonstandard you're forced to install a driver from source. Then do all
the system updates, and immediately reboot.

Ideally, nothing should break, because all the upgrades will have
proceeded cleanly and migrated everything forward nicely. Doesn't
always happen. The more third-party software and nonstandard hardware
you throw into the mix, the more likely you will run across one of these
corner cases.
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Old 02-21-2012, 02:51 PM
Ljubomir Ljubojevic
 
Default Ways To Practice Breaking My System?

On 02/21/2012 04:00 PM, Warren Young wrote:
> - Build and install some needed driver from source, yum upgrade
> repeatedly, implicitly upgrade kernel, forget to rebuild the driver
> against the new kernel, reboot, boom.

Use ElRepo repository for drivers. They use kmod so it works on new
kernel without recompilation, just works. kmod is based on
symlinks/weak-updates.

If there is something ElRepo does not have, and it is open source, they
will be happy to include it. Even if it is proprietary, they could build
you spec (+ instructions ) for kmod package.

--

Ljubomir Ljubojevic
(Love is in the Air)
PL Computers
Serbia, Europe

Google is the Mother, Google is the Father, and traceroute is your
trusty Spiderman...
StarOS, Mikrotik and CentOS/RHEL/Linux consultant
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Old 02-21-2012, 10:27 PM
Jobst Schmalenbach
 
Default Ways To Practice Breaking My System?

On Tue, Feb 21, 2012 at 08:00:17AM -0700, Warren Young (warren@etr-usa.com) wrote:
> On 2/21/2012 5:57 AM, Boris Epstein wrote:
> > Things like boot process rarely break.
>
> - Get asked to configure the foo service, get it all working, forget to
> add it to init.d, use it happily for months, reboot, fail to notice the
> service's absence until someone gives a misleading bug report. ("The
> foo service has crashed!") Then I have to go chasing it, handicapped by
> being half a year separated from the last time I looked at it.
>

I am glad to see I am NOT the only one doing this ... ;-)
You made my day ;-)

Jobst



--
The future isn't what it used to be (it never was).

| |0| | Jobst Schmalenbach, jobst@barrett.com.au, General Manager
| | |0| Barrett Consulting Group P/L & The Meditation Room P/L
|0|0|0| +61 3 9532 7677, POBox 277, Caulfield South, 3162, Australia
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