This time it took a while until I experienced some network problems with dhclient3. I though that the problem got solved during an update, but it seems that it wasn't since I had once more a problem. This time I use the command dhclient3 eth0, the network restarted properly as expected. I did some more investigations while the network wasn't configured. Here are the resutls: emmanuel@uber ~> ifconfig eth0 Link encap:Ethernet HWaddr 00:11:09:D3:91:AD inet6 addr: fe80::211:9ff:fed3:91ad/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1 errors:0 dropped:0 overruns:0 frame:0 TX packets:5 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:247 (247.0 b) TX bytes:378 (378.0 b) Interrupt:23 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:16436 Metric:1 RX packets:2211 errors:0 dropped:0 overruns:0 frame:0 TX packets:2211 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:199255 (194.5 KiB) TX bytes:199255 (194.5 KiB) Interface eth0 is kind of up but not well configured. I can't ping my router. emmanuel@uber ~> ps eaxf 5068 ? Ss 0:00 /bin/sh /etc/hotplug/net.ifup eth0=hotplug 5562 ? S 0:00 \_ ifup eth0=hotplug 5567 ? S 0:00 \_ dhclient3 -pf /var/run/dhclient.eth0.pid -lf /var/run/dhclient.eth0.leases eth0 dhclient3 is still running as usual but the interface eth0 can't be used. emmanuel@uber ~> sudo strace -p 5567 Process 5567 attached - interrupt to quit select(7, [5 6], [], [], {6863, 383000} This is the single line of output I got from the process, it seems to be waiting for some input. I eventually got bored of waiting so I moved on. emmanuel@uber ~> sudo lsof -c dhclient3 COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME dhclient3 5567 dhcp cwd DIR 8,3 4096 1913398 /etc/hotplug dhclient3 5567 dhcp rtd DIR 8,3 4096 2 / dhclient3 5567 dhcp txt REG 8,3 499008 392566 /sbin/dhclient3 dhclient3 5567 dhcp mem REG 0,0 0 [heap] (stat: No such file or directory) dhclient3 5567 dhcp mem REG 8,3 94448 835682 /lib/ld-2.3.5.so dhclient3 5567 dhcp mem REG 8,3 15568 834013 /lib/libcap.so.1.10 dhclient3 5567 dhcp mem REG 8,3 1261816 835695 /lib/libc-2.3.5.so dhclient3 5567 dhcp mem REG 8,3 44056 835703 /lib/libnss_files-2.3.5.so dhclient3 5567 dhcp mem REG 8,3 36112 835701 /lib/libnss_compat-2.3.5.so dhclient3 5567 dhcp mem REG 8,3 87072 835700 /lib/libnsl-2.3.5.so dhclient3 5567 dhcp mem REG 8,3 39936 835705 /lib/libnss_nis-2.3.5.so dhclient3 5567 dhcp 0u CHR 1,3 2622 /dev/null dhclient3 5567 dhcp 1u CHR 1,3 2622 /dev/null dhclient3 5567 dhcp 2u CHR 1,3 2622 /dev/null dhclient3 5567 dhcp 3w REG 8,3 0 327128 /var/run/dhclient.eth0.leases dhclient3 5567 dhcp 4w REG 8,3 0 327130 /var/run/dhclient.eth0.pid dhclient3 5567 dhcp 5u IPv4 8475 UDP *:bootpc dhclient3 5567 dhcp 6u sock 0,4 8470 can't identify protocol On another window I did to see if the current dhclient will react to network changes: sudo strace -p 5567 -ocurrent-dhclient3 Then I launched a new instance of dhclient3 this time with an interface emmanuel@uber ~/dhclient3> sudo strace -onew-dhclient3 dhclient3 eth0 Internet Systems Consortium DHCP Client V3.0.2 Copyright 2004 Internet Systems Consortium. All rights reserved. For info, please visit http://www.isc.org/products/DHCP sit0: unknown hardware address type 776 sit0: unknown hardware address type 776 Listening on LPF/eth0/00:11:09:d3:91:ad Sending on LPF/eth0/00:11:09:d3:91:ad Sending on Socket/fallback DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 8 DHCPOFFER from 192.168.1.1 DHCPREQUEST on eth0 to 255.255.255.255 port 67 DHCPACK from 192.168.1.1 bound to 192.168.1.200 -- renewal in 37234 seconds. From this point on the network works. emmanuel@uber ~/dhclient3> ps eaxf 5068 ? Ss 0:00 /bin/sh /etc/hotplug/net.ifup eth0=hotplug 5562 ? S 0:00 \_ ifup eth0=hotplug 5567 ? S 0:00 \_ dhclient3 -pf /var/run/dhclient.eth0.pid -lf /var/run/dhclient.eth0.leases eth0 7015 ? Ss 0:00 dhclient3 eth0 The first dh3client seems to have reacted a little bit to the network changes, but it still hangs at the same place: select(7, [5 6], [], [], {6061, 723000}) = 1 (in [6], left {6015, 913000}) read(6, "\0\21\t\323\221\255\0\21\330u\276\223\10\0E\0\2@\0\0\0"..., 1536) = 590 select(7, [5 6], [], [], {6016, 92307}) = 1 (in [6], left {6016, 91000}) read(6, "\0\21\t\323\221\255\0\21\330u\276\223\10\0E\0\2@\0\0\0"..., 1536) = 590 select(7, [5 6], [], [], {6016, 89847} emmanuel@uber ~/dhclient3> sudo strace -p 7077 If we attach to the new dhclient3 process with the command strace it shows a different output. See attachment in next comment.