Hostapd doesn't launch with udev - udev

Question

I have a problem, I want to launch a script to start "hostapd" when I insert a vga/hdmi adapter on my Asus E200ha.
The script works well when I launch it directly in a commmand line but don't work when it's called by "udev"
This is the line for the udev's capture:
ACTION=="change", SUBSYSTEM=="drm", ENV{HOTPLUG}=="1", RUN="/home/user/hotspot.sh"
This is the script "hotspot.sh"
#!/bin/bash
exec > /var/log/hotplug-vga.log 2>&1;
service NetworkManager stop
killall wpasupplicant
hostapd -dd /etc/hostapd/hostapd.conf &
This is the "hostapd.conf" file
interface=wlan0
ieee80211n=1
driver=nl80211
ssid=chingpro
hw_mode=g
channel=6
ctrl_interface=/var/run/hostapd
ctrl_interface_group=0
When I execute the instruction "/usr/sbin/hostapd /home/user/hostapd.sh", all work fine:
wpasupplicant: aucun processus trouvé
random: Trying to read entropy from /dev/random
Configuration file: /etc/hostapd/hostapd.conf
ctrl_interface_group=0
nl80211: TDLS supported
nl80211: TDLS external setup
nl80211: Supported cipher 00-0f-ac:1
nl80211: Supported cipher 00-0f-ac:5
[...]
nl80211: assocresp_ies - hexdump(len=10): 7f 08 04 00 00 02 00 00 00 40
nl80211: Set wlan0 operstate 0->1 (UP)
netlink: Operstate: ifindex=18 linkmode=-1 (no change), operstate=6 (IF_OPER_UP)
wlan0: interface state UNINITIALIZED->ENABLED
wlan0: AP-ENABLED
wlan0: Setup of interface done.
ctrl_iface not configured!
[...]
But when I connect my vga/hdmi, I can see that my script is executed with the log inside the "/var/log/hotplug-vga.log" but the launch of "hostapd" fail:
wpasupplicant: no process found
random: Trying to read entropy from /dev/random
Configuration file: /etc/hostapd/hostapd.conf
ctrl_interface_group=0
nl80211: TDLS supported
nl80211: TDLS external setup
nl80211: Supported cipher 00-0f-ac:1
nl80211: Supported cipher 00-0f-ac:5
nl80211: Supported cipher 00-0f-ac:2
nl80211: Supported cipher 00-0f-ac:4
nl80211: Supported cipher 00-0f-ac:6
nl80211: Supported cipher 00-0f-ac:13
nl80211: Supported cipher 00-0f-ac:11
nl80211: Supported cipher 00-0f-ac:12
nl80211: Supports Probe Response offload in AP mode
nl80211: Using driver-based off-channel TX
nl80211: Driver-advertised extended capabilities (default) - hexdump(len=8): 04 00 00 00 00 00 00 40
nl80211: Driver-advertised extended capabilities mask (default) - hexdump(len=8): 04 00 00 00 00 00 00 40
nl80211: Use separate P2P group interface (driver advertised support)
nl80211: Enable multi-channel concurrent (driver advertised support)
nl80211: use P2P_DEVICE support
nl80211: interface wlan0 in phy phy15
nl80211: Set mode ifindex 18 iftype 3 (AP)
nl80211: Setup AP(wlan0) - device_ap_sme=0 use_monitor=0
nl80211: Subscribe to mgmt frames with AP handle 0x557d15b300e0
nl80211: Register frame type=0xb0 (WLAN_FC_STYPE_AUTH) nl_handle=0x557d15b300e0 match=
nl80211: Register frame command failed (type=176): ret=-114 (Operation already in progress)
nl80211: Register frame match - hexdump(len=0): [NULL]
nl80211: Could not configure driver mode
nl80211: deinit ifname=wlan0 disabled_11b_rates=0
nl80211: Remove monitor interface: refcount=0
nl80211: Remove beacon (ifindex=18)
netlink: Operstate: ifindex=18 linkmode=0 (kernel-control), operstate=6 (IF_OPER_UP)
nl80211 driver initialization failed.
hostapd_interface_deinit_free(0x557d15b294c0)
hostapd_interface_deinit_free: num_bss=1 conf->num_bss=1
hostapd_interface_deinit(0x557d15b294c0)
wlan0: interface state UNINITIALIZED->DISABLED
hostapd_bss_deinit: deinit bss wlan0
wlan0: AP-DISABLED
hostapd_cleanup(hapd=0x557d15b2a730 (wlan0))
hostapd_free_hapd_data: Interface wlan0 wasn't started
hostapd_interface_deinit_free: driver=(nil) drv_priv=(nil) -> hapd_deinit
hostapd_interface_free(0x557d15b294c0)
hostapd_interface_free: free hapd 0x557d15b2a730
hostapd_cleanup_iface(0x557d15b294c0)
hostapd_cleanup_iface_partial(0x557d15b294c0)
hostapd_cleanup_iface: free iface=0x557d15b294c0
I spent a lot of hours to understand the difference for sending this script directly or by udev but without success for the moment.
I'm working on a fresh "debian buster" install
I install Ubuntu 18.04 with the same scripts and i have the same problems : the script work well in command line but fail when it is launched by udev!
Thanks for your help

Answer 1

First, are you sure the "service NetworkManager stop" actually runs? Lot of problems in "runs manually but not from cron/udev/initscript" is caused by differences in PATH. It's possible "service" is not on path from udev.
Second, is that really command you should be running? On https://bugs.launchpad.net/ubuntu/+source/wpa/+bug/1289047 the following solution is recommended:
nmcli nm wifi off
rfkill unblock wlan
or in case of suspicous path perhaps it would be better to write it as
/usr/bin/nmcli nm wifi off
/usr/sbin/rfkill unblock wlan

Answer 2

I know it is an old question, but I also struggled with this problem and found a workround.
I dont know why hostapd behaves differently when called from udev, however the page
https://wiki.archlinux.org/index.php/udev#Spawning_long-running_processes
gives a solution, yet conceived for a different problem. The idea is to handle the execution of hostapd to a daemon outside udev, in this case the atd. This daemon is in the package 'at' at debian. Once installed, you can call hostapd from the udev script with
echo "/usr/sbin/hostapd -B -P /path/to/pidfile /path/to/hostapd.config" | at now