eth0 does not get an IP-address from DHCP anymore

[Anders Häggström]

I installed Ubuntu Feisty (AMD64) using this manual, exept for the
last step (install the ubuntu-desktop):
https://help.ubuntu.com/7.04/installation-guide/amd64/linux-upgrade.html
A really nice small setup if you want to have a minimal installation
and a good start for custom installs.

After my installation everything was working as expected but suddenly
after a reboot my network didn't receive DHCP-leases anymore. I'm
stuck and need help to solve this problem.

I have searched the net for different solutions but haven't found any
that matches my problem.

The obvious question is "What did you do before the reboot?", as those
things might have messed things up.
I only updated the installation with "# aptitude update && aptitude
upgrade" and installed a fiew packages using "# aptitude install acpid
cpufreqd sensors"

If I boot the computer from the live-CD I get an IP-number from my
DHCP-server, so there should be support for the hardware. And I had
the network up and running during the upgrade and the installation,
and the network (outside my computer, DHCP-server, switch, cables etc)
are fully functional.

Here are a fiew commands I have tried (in chronological order).
If you need more information about my system, or have ideas on how to
slove it, please tell me.
I think it might have something to do with the "Permission denied"
output, but I can't figure out what.

// Start Of Testing
# ps -aux | grep dhcp
dhcp      4632  0.0  0.1  14092   736 ?        S<s  23:09   0:00
dhclient3 -pf /var/run/dhclient.eth0.pid -lf
/var/lib/dhcp3/dhclient.eth0.leases eth0
root      4669  0.0  0.1   3860   584 tty1     S+   23:15   0:00 grep dhcp

# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:16:E7:56:C1:0E
          BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)
          Interrupt:23 Base address:0x4000

# /etc/init.d/networking restart
There is already a pid file /var/run/dhclient.eth0.pid with pid 6847440
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

SIOCSIFADDR: Permission denied
SIOCSIFFLAGS: Permission denied
SIOCSIFFLAGS: Permission denied
Listening on LPF/eth0/00:16:e7:56:c1:0e
Sending on   LPF/eth0/00:16:e7:56:c1:0e
Sending on   Socket/fallback
receive_packet failed on eth0: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 5
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 6
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 10
send_packet: Network is down
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 10
send_packet: Network is down
No DHCPOFFERS received.
No working leases in persistent database - sleeping.

# ifdown eth0
There is already a pid file /var/run/dhclient.eth0.pid with pid 5072
killed old client process, removed PID file
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

Listening on LPF/eth0/00:16:e7:56:c1:0e
Sending on   LPF/eth0/00:16:e7:56:c1:0e
Sending on   Socket/fallback

# ifconfig eth0 up
(no output)

# ifup eth0
There is already a pid file /var/run/dhclient.eth0.pid with pid 6847440
Internet Systems Consortium DHCP Client V3.0.4
Copyright 2004-2006 Internet Systems Consortium.
All rights reserved.
For info, please visit http://www.isc.org/sw/dhcp/

SIOCSIFADDR: Permission denied
SIOCSIFFLAGS: Permission denied
SIOCSIFFLAGS: Permission denied
Listening on LPF/eth0/00:16:e7:56:c1:0e
Sending on   LPF/eth0/00:16:e7:56:c1:0e
Sending on   Socket/fallback
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8
DHCPOFFER from 172.16.2.1
DHCPREQUEST on eth0 to 255.255.255.255 port 67
DHCPACK from 172.16.2.1
SIOCSIFADDR: Permission denied
SIOCSIFFLAGS: Permission denied
SIOCSIFNETMASK: Permission denied
SIOCSIFBRDADDR: Permission denied
SIOCSIFFLAGS: Permission denied
SIOCADDRT: Operation not permitted
[CTRL + C] (process never exit, so I terminated it after 5 minutes)

# ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:16:E7:56:C1:0E
          inet6 addr: fe80::216:e7ff:fe56:c10e/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:17 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1963 (1.9 KiB)  TX bytes:1152 (1.1 KiB)
          Interrupt:23 Base address:0x4000

// End Of Testing

Thanks,
Anders