There seems to be no way to do it within Network Manager. Editing /etc/network/interfaces on the other hand is clumsy and causes delays in later editions of Ubuntu like 12.04 (see this and this). In the end the solution offered here turns out to be best (for now), by adding the ethtool command to rc.local:
sudo -H gedit /etc/rc.local
ethtool -s eth0 autoneg off speed 100 duplex full # put this above 'exit 0'
A bug with Network Manager obviously can be solved this way:
First you need anyway purge hostapd together with configuration:
sudo apt-get purge hostapd
Then try to reinstall network-manager, and this way your configuration of network-manager will be saved:
sudo apt-get install --reinstall -fmu network-manager
where -f is fix-broken, -m is fix-missing and -u is show upgraded
sudo reboot
OR completely purge hostapd & network-manager together with their configurations and again freshly install network-manager by single command:
sudo apt-get purge -y hostapd && sudo apt-get purge -y network-manager && sudo apt-get install network-manager && sudo reboot
For a chance to have hostapd installed my opinion you need to go step-by-step this guide:
WifiDocs / MasterMode
Then, if success you can begin stepping second guide to setup your wifi from there:
Using hostapd on Ubuntu to create a wifi access point
Cited the part 5.Troubleshooting from second guide:
If you have network-manager configured to use your wifi card, you
should disable auto-connect for all the wireless connections.
Otherwise, it may interfere with hostapd. If some frequencies are
disabled, make sure your driver is set to use the right regulatory
domain. You can see the current one with:
iw reg get
If it says country 00, you need to set it manually, in
/etc/default/crda. To set it manually you need (at least for some
cards) to have cfg80211 and mac80211 installed as kernel modules. You
can check if they’re installed as modules by using:
zcat /proc/config.gz
Look for CONFIG_CFG80211=m, if it says “=y” then it’s compiled into
the kernel, and you’ll need to re-install your kernel. If you’re using
an Atheros card, you may also need to set the region in the driver. Do
this by adding “cfg80211 ieee80211_regdom=US” to /etc/modules
Last sentence is about your country code sure.
Best Answer
In my case, I had a left over entry for eth0 in /etc/network/interfaces which was configured to use DHCP, but since there was no ethernet plugged into eth0 DHCP could never succeed.
Check /etc/network/interfaces, comment out everything other than:
auto lo iface lo inet loopback
Then reboot and hopefully network-manager will start as expected.