loopback doesn't come up on boot

[ultralame]

When I boot/reboot, my dapper installation comes up to the GUI. However, the network is not started.

HEre's what I have to do:

From the GUI, bring up the Networking panel and activate eth0.
Run a script that creates the loopback interface
init 3
init 2
(those last parts restart all my services/daemons with the network up)- is there a better way to do that?


Any ideas? I am not sure what to post here. The scripts in rcS.d and rc2.d appear to be correct (the loopback is created and then eth0 is started).

I can't seem to find anything in /var/log/syslog, /var/log/messages or dmesg that indicates a problem.

Any ideas? How can I debug this? Is there a way to boot slowly, toggle startup scripts as I go, and then read the output of each one?

Thanks!

[Jaime E. Villate]

I had the same problem. I could get the loopback interface back with
sudo ifconfig lo up
but the problems continued because "lo" was not being brought up automatically at bootime. I finally found the cause of the problem by following the advice of varunus in thread 48557: run
sudo /etc/init.d/networking restart
manually to detect the problem: it pinpointed a simple syntax error in /etc/network/interfaces which was causing the problem.

[ultralame]

OK- that's interesting. But what was the Syntax Error you found? I have two scripts:
/etc/init.d/networking
/etc/init.d/loopback

In rcS.d, the loopback is run first, then the networking.

Notice in the networking script, the START command runs
ifup -a
while the RESTART command runs
ifdown -a --exclude=lo
ifup -a --exclude=lo

Is this the problem? That when the machine starts, it screws up the lo interface, but not when you use STOP or RESTART?

/etc/init.d/networking:
#!/bin/sh -e
### BEGIN INIT INFO
# Provides: networking
# Required-Start: mountvirtfs ifupdown $local_fs
# Default-Start: S
# Default-Stop: 0 6
### END INIT INFO

PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin"

[ -x /sbin/ifup ] || exit 0

. /lib/lsb/init-functions


case "$1" in
start)
log_action_begin_msg "Configuring network interfaces"
type usplash_write >/dev/null 2>/dev/null && usplash_write "TIMEOUT 120" || true
if [ "$VERBOSE" != no ]; then
if ifup -a; then
log_action_end_msg $?
else
log_action_end_msg $?
fi
else
if ifup -a >/dev/null 2>&1; then
log_action_end_msg $?
else
log_action_end_msg $?
fi
fi
type usplash_write >/dev/null 2>/dev/null && usplash_write "TIMEOUT 15" || true
;;

stop)
if sed -n 's/^[^ ]* \([^ ]*\) \([^ ]*\) .*$/\2/p' /proc/mounts |
grep -qE '^(nfs[1234]?|smbfs|ncp|ncpfs|coda|cifs)$'; then
log_warning_msg "not deconfiguring network interfaces: network shares still mounted."
exit 0
fi

log_action_begin_msg "Deconfiguring network interfaces"
if [ "$VERBOSE" != no ]; then
if ifdown -a --exclude=lo; then
log_action_end_msg $?
else
log_action_end_msg $?
fi
else
if ifdown -a --exclude=lo >/dev/null 2>/dev/null; then
log_action_end_msg $?
else
log_action_end_msg $?
fi
fi
;;

force-reload|restart)
log_action_begin_msg "Reconfiguring network interfaces"
ifdown -a --exclude=lo || true
if ifup -a --exclude=lo; then
log_action_end_msg $?
else
log_action_end_msg $?
fi
;;

*)
echo "Usage: /etc/init.d/networking {start|stop|restart|force-reload}"
exit 1
;;
esac

exit 0

/etc/init.d/loopback:
#!/bin/sh -e
#
# loopback - brings up the loopback (127.0.0.1) network device so that
# DHCP and other such things will work
#

# Check the package is still installed
[ -x /sbin/ifup ] || exit 0

# Get LSB functions
. /lib/lsb/init-functions
. /etc/default/rcS

case "$1" in
start)
[ -d /var/run/network ] || mkdir /var/run/network

log_begin_msg "Starting basic networking..."
# if ifup -v --allow auto lo; then
if ifup -v auto lo; then
log_end_msg 0
else
log_end_msg $?
fi
;;
stop)
log_begin_msg "Stopping basic networking..."
if ifdown lo; then
log_end_msg 0
else
log_end_msg $?
fi
;;
restart|force-reload)
exit 0
;;
*)
echo "Usage: /etc/init.d/loopback {start|stop|restart|force-reload}"
exit 1
;;
esac

exit 0

[NigO]

I'm having a similar problem with one machine.
/etc/network/interfaces contains (XX's replace valid internal addresses)
auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 10.XX.XX.XX
netmask 255.255.255.0
gateway 10.XX.XX.XX


#iface eth1 inet dhcp

#auto eth2
#iface eth2 inet dhcp

#auto ath0
#iface ath0 inet dhcp

#auto wlan0
#iface wlan0 inet dhcp



On boot loopback doesn't come up. I need to use
sudo ifconfig lo up

If I do
sudo ifup --verbose lo
before bringing the interface up instead, I get
ifup: interface lo already configured


and ifup -a
doesn't bring it up either.
ifconfig -a shows that it is configured, but not up.

If I edit the standard /etc/init.d/networking script so that restart doesn't exclude lo (see previous messages above), then /etc/init.d/networking restart does fix the problem.

Any clues where to go next?