How to successfully restart a network without reboot over SSH?

Turns out this is a "feature". The only supported way of restarting an interface in Ubuntu Server is sudo ifdown eth0 && sudo ifup eth0

https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1301015


ifdown, ifup didn't work for me (likely SSH connection timeout before the second command). What did work was:

sudo service network-manager restart

This was on a 14.04 ubuntu-desktop system.


What's changed is they don't want you "bouncing" the network anymore. stopping, and starting, still work. restart no longer works. I just "solved" this "problem", that is to say I got the old behavior back. To revert to prior behavior: Take a 13.10 /etc/init/networking.conf file and replace the 14.04 file with it. (edit: clarified which replaces which)

The process looks like this:

(Just before this, I configured my /etc/network/interfaces for eth1 on a 192.168.117.x address)

"/etc/network/interfaces" 16L, 413C written  
root@1404-Anode:~# service networking restart  
stop: Job failed while stopping  
start: Job is already running: networking  
root@1404-Anode:~# echo "hmm, wth?"
hmm, wth?
root@1404-Anode:~# ifconfig  
eth0      Link encap:Ethernet  HWaddr 00:0c:29:d6:a8:19  
          inet addr:192.168.115.105  Bcast:192.168.115.255  Mask:255.255.255.0  
          inet6 addr: 2002:4077:9050:1234:a08c:29c1:ce9b:a57b/64 Scope:Global  
          inet6 addr: fe80::20c:29ff:fed6:a819/64 Scope:Link  
          inet6 addr: 2002:4077:9050:1234:20c:29ff:fed6:a819/64 Scope:Global  
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1  
          RX packets:646 errors:0 dropped:0 overruns:0 frame:0  
          TX packets:531 errors:0 dropped:0 overruns:0 carrier:0  
          collisions:0 txqueuelen:1000  
          RX bytes:58748 (58.7 KB)  TX bytes:75465 (75.4 KB)  
(lo removed here)  
root@1404-Anode:~# cd /etc/init
root@1404-Anode:/etc/init# diff networking.conf.1310 networking.conf.1404  
13c13  
<       and (stopped udevtrigger or container)) or runlevel [2345]  
---  
>     and (stopped udevtrigger or container)) or runlevel [2345] or stopped  networking   >RESULT=failed PROCESS=post-stop EXIT_STATUS=100  
16a17,20  
>     if [ "$UPSTART_EVENTS" = "stopped" ] && [ "$UPSTART_JOB" = "networking" ] && [ "$EXIT_STATUS" = "100" ]; then  
>         exit 0  
>     fi  
>  
21a26,31  
>     if [ -z "$UPSTART_STOP_EVENTS" ]; then  
>        echo "Stopping or restarting the networking job is not supported."  
>         echo "Use ifdown & ifup to reconfigure desired interface."  
>         exit 100  
>     fi  
root@1404-Anode:/etc/init#  

Do the same for /etc/init.d/networking script, which is what the /etc/init/networking.conf file references/calls.

root@1404-Anode:/etc/init# cp networking.conf.1310 networking.conf  
root@1404-Anode:/etc/init# cd ../init.d  
root@1404-Anode:/etc/init.d# diff networking.1404 networking.1310  
15d14  
< STATEDIR="$RUN_DIR/state"
21a21,27
> # Make sure that it's clear to the user that they shouldn't use this
> # script under upstart
> if init_is_upstart; then
>       echo "ERROR: Calling a sysvinit script on a system using upstart isn't supported. Please use the 'service' command instead."  
>       exit 1
> fi
>
52,54d57
<       if ! chown root:netdev "$RUN_DIR" ; then
<           log_warning_msg "can't chown $RUN_DIR"
<       fi
160,162d162
<       if init_is_upstart; then
<               exit 1
<       fi
166c166
<       state=$(ifquery --state)
---
>       state=$(cat /run/network/ifstate)
root@1404-Anode:/etc/init.d# cp networking.1310 networking
root@1404-Anode:/etc/init.d# service networking restart
networking stop/waiting
networking start/running
root@1404-Anode:/etc/init.d# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0c:29:d6:a8:19
          inet addr:192.168.115.105  Bcast:192.168.115.255  Mask:255.255.255.0
          inet6 addr: 2002:4077:9050:1234:a08c:29c1:ce9b:a57b/64 Scope:Global
          inet6 addr: fe80::20c:29ff:fed6:a819/64 Scope:Link
          inet6 addr: 2002:4077:9050:1234:20c:29ff:fed6:a819/64 Scope:Global
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:3398 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2545 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:318654 (318.6 KB)  TX bytes:418804 (418.8 KB)

eth1      Link encap:Ethernet  HWaddr 00:0c:29:d6:a8:23
          inet addr:192.168.117.105  Bcast:192.168.117.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fed6:a823/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:98 errors:0 dropped:58 overruns:0 frame:0
          TX packets:15 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:20055 (20.0 KB)  TX bytes:1226 (1.2 KB)
(lo removed)
root@1404-Anode:/etc/init.d# echo "hah, it works! *8^)"
Hah, it works! *8^)
root@1404-Anode:/etc/init.d#

(note: the steps where I scp'd the 1310 versions into the 1404 system are omitted for brevity). 

Obviously there's a reason they put a defensive exit in there, but they don't bother to really output what's going on very well.

An entry does go into /var/log/upstart/networking.log when you try, that looks like:

Stopping or restarting the networking job is not supported.  
Use ifdown & ifup to reconfigure desired interface.  

But they really could/should have output that as the dialog message when you try service networking restart. ah well. figured it out and even a old-way work around.

EDIT: I have found this causes an unintentional triggering of the script controlled by /etc/init/failsafe.conf which is undesirable as it causes a 120 second timeout delay in every boot up... as well as perhaps masking actual misconfigurations/network issues which this delay's appearance would indicate, but it's already showing all the time. (e.g. An unplugged cable, which was allowing access to a network file share mapped in /etc/fstab, for instance)

In any case, I will figure out what is causing this always hitting the timeout, and post a fix when I find it.