Shellscript for MAC-check.

i need a sh-script which will issue a reboot unless the MAC adress of eth0 and eth1 are the correct ones.

(For some reason, a system we have swaps eth0 and eth1 around about once in every 20 reboots.)
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GnsConnect With a Mentor Commented:
just for completeness... The very simple "check-n-reboot" script:
REALMAC="$(/sbin/ifconfig eth0 | awk '$0 ~ /HWaddr/ {print $NF}')"

if [ "$ETH0MAC" != "$REALMAC" ]
  sleep 3
# End of script

Needs to run after network initialization... perhaps from /etc/rc.local (or similar construct that come very late in the bootup process).

-- Glenn
Hi j2,

> (For some reason, a system we have swaps eth0 and eth1 around about once in every 20 reboots.)
Are you sure ? MAC addresses are hardcoded into the device :o)

Linux on booting names the dvices sequentially (if they have not been already named) ... I guess you are being troubled by that naming


Why that complicated?! How about this script:

#! /bin/bash
#Idea by Igor Puschner
ifconfig eth0 down
ifconfig eth1 down
ifconfig eth0 hw ether XX:XX:XX:XX:XX:XX
ifconfig eth1 hw ether YY:YY:YY:YY:YY:YY
ifconfig eth0 up
ifconfig eth1 up


Just replace XX:XX:XX:XX:XX:XX with the Mac Adress for eth0, and YY:YY:YY:YY:YY:YY with the MAc adress for eth1.
It should work fine, as long as eth0 and eth1 have both the same speed (i guess so).
No reboot needed!

Greets Igor
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j2Author Commented:
ipuschner: Sorry, that is not what i want. For more then one reason, i _need_ the system to reboot when it happens.

Gns: Thanks, i realize that i simply do not master the "if" statement in shell programming. Thanks.
j2Author Commented:
sunny coder: Well, whatever the reason is, some times the "wrong" NIC becomes eth0, which can be a nuisance since the system is a firewall.
:-) j2.
One not to uncommon solution is to have heterogenous NICs... So that you actually load different modules for the different interfaces.
I have a nagging feeleing I've seen something very nice for this with homogenous NICs (very likely would be completely driver dependant)... Oh for better memory...:-)

-- Glenn
j2Author Commented:
Nope, Two different NIC's, different line-speeds, and 802.11q enabled on one :)

I figure that running your script as an "up" script (debian) for eth1 should take care of it.

Have a pleasent weekend!
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