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Revolucion for Monica
Asked: 2016-06-06 06:37:41 +0800 CST

Service isc-dhcp-server fails to start

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I'm currently working on a project of making an highly secured router with my RaspberryPi to navigate anonymously on the net. Yet, I'm not able to correctly configurate the daemon to finalise the wifi the Internet connection to the new server:

Indeed, when I do:

:~ $ sudo service isc-dhcp-server start

I get:

Job for isc-dhcp-server.service failed. See 'systemctl status isc-dhcp-server.service' and 'journalctl -xn' for details.

Here are my /etc/dhcp/dhcpd.conf settings

authoritative;

#added

subnet 192.168.42.0 netmask 255.255.255.0{
        range 192.168.42.10 192.168.42.50;
        option broadcast-adress 192.168.42.255;
        option routers 192.168.42.1;
        default-lease-time 600;
        max-lease-time 7200;
        option domain-name "local";
        option domain-name-servers 8.8.8.8, 8.8.4.4;
}

And here are my /etc/network/interfaces settings:

source-directory /etc/network/interfaces.d

auto lo
iface lo inet loopback
iface eth0 inet manual

allow-hotplug wlan0
iface wlan0 inet static
adress 192.168.42.1
netmask 255.255.255.0

iface wlan0 inet dhcp

iface eth0 inet manual

allow-hotplug wlan0
iface wlan0 inet static
adress 192.168.42.1
netmask 255.255.255.0

iface wlan0 inet dhcp
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

allow-hotplug wlan1
iface wlan1 inet manual
    wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf

up iptables-restore < /etc/iptables.ipv4.nat

My RaspberryPi is wirely connected but has a wifi dongle

Here is the systemctl status isc-dhcp-server.service

:~ $ systemctl status isc-dhcp-server.service
● isc-dhcp-server.service - LSB: DHCP server
   Loaded: loaded (/etc/init.d/isc-dhcp-server)
   Active: failed (Result: exit-code) since Tue 2016-06-07 00:13:45 CEST; 53s ago
  Process: 18098 ExecStart=/etc/init.d/isc-dhcp-server start (code=exited, status=1/FAILURE)

Some parts are written with a scary red...

and here is the journalctl

-- Logs begin at Mon 2016-06-06 21:17:01 CEST, end at Tue 2016-06-07 00:18:32 CEST. --
Jun 07 00:13:45 raspberrypi isc-dhcp-server[18098]: than a configuration issue please read the section on submitting
Jun 07 00:13:45 raspberrypi isc-dhcp-server[18098]: bugs on either our web page at www.isc.org or in the README file
Jun 07 00:13:45 raspberrypi isc-dhcp-server[18098]: before submitting a bug.  These pages explain the proper
Jun 07 00:13:45 raspberrypi isc-dhcp-server[18098]: process and the information we find helpful for debugging..
Jun 07 00:13:45 raspberrypi isc-dhcp-server[18098]: exiting.
Jun 07 00:17:01 raspberrypi CRON[18118]: pam_unix(cron:session): session opened for user root by (uid=0)
Jun 07 00:17:01 raspberrypi CRON[18122]: (root) CMD (   cd / && run-parts --report /etc/cron.hourly)
Jun 07 00:17:01 raspberrypi CRON[18118]: pam_unix(cron:session): session closed for user root
Jun 07 00:18:32 raspberrypi sudo[18139]: pi : TTY=pts/0 ; PWD=/home/pi ; USER=root ; COMMAND=/bin/journalctl -xn
Jun 07 00:18:32 raspberrypi sudo[18139]: pam_unix(sudo:session): session opened for user root by pi(uid=0)
networking

2 Answers

  1. Best Answer

    There was to things:

    The most obvious one was to write address with two "d" here:

    subnet 192.168.42.0 netmask 255.255.255.0{
        range 192.168.42.10 192.168.42.50;
        option broadcast-adress 192.168.42.255;
        option routers 192.168.42.1;
        default-lease-time 600;
        max-lease-time 7200;
        option domain-name "local";
        option domain-name-servers 8.8.8.8, 8.8.4.4;
}

    The second one was to start the wireless network by running:

    sudo ifup wlan0

    And I would have been able to start service isc-dhcp-server I made it thanks to this raspberrypihq tutorial to turn a RPi into a routeur.

    Yet, I now have issues to run sudo update-rc.d isc-dhcpd-server enable. Any help would be warmly welcomed!

    • 3

  2. IN CASE IT HELPS ANYONE I've just been right through this exasperating issue, on DietPi (Debian Buster) on a Pi Zero W and HAVE BOTTOMED THE PROBLEM.

    isc-dhcp-server is excellent but DOES HAVE this quirk, as noted by the original enquirer above. I've bottomed the problem - it's not a bug - and this is the detail of the reason:

    isc-dhcp-server refuses (throws an error) if it cannot see an UP ethernet network subnet at launch time; it DOESN'T (contrary to some commentators) require an actual connection TO the ethernet port to which it is associated.

When developing a WiFi Hotspot device, its normally a case of using hostapd as the AP server function (which re-configures the WiFi hardware to switch to AP mode) and alongside hostapd, you need a dhcp server like isc-dhcp-server to provide the IP address leasing service.

SO: normally the start point, is a WiFi device which at boot, was configured as a CLIENT device, but needs to be switched to HOST mode to act as hotspot. So an early step is to set wlan0 (or whatever) DOWN, prior to launching hostapd.

    BUT that situation, is immediately one of those which isc-dhcp-server does not like: if you try to start it before hostapd, it will fail, complaining that there is no subnet for it to listen on.

    So you may innocently then try, adding a new IP address (for the host) to your wlan0 (or equiv) and re-trying: THAT WON'T WORK EITHER, because although you now have a new IP attached to the Ethernet port, you will also find you cannot set it 'UP' (ip link set wlan0 up will FAIL). This is because the port is 'tainted' by the still-active stale address and the wpa-supplicant process which was using it.

LONG STORY SHORT: you need to kill wpa-supplicant, to "free" the old address / FLUSH the ip settings for the port / THEN add the new IP address for host ; EVEN THEN, you'll find isc-dhcp-server STILL won't start, because you can't set the interface up - yet. Finally - run hostapd now, before isc, and IT will (in reconfiguring the chipset) also SET the wlan0 interface, to UP. So now - finally - you CAN run isc-dhcp-server, and it will start cleanly, and your hotspot will be up.

    It's taken me about five hours, I hope this saves someone some time. My distilled note:

    SORTING ISC-DHCP-SERVER alongside HOSTAPD: THE SOLUTION

    YOU HAVE TO follow THIS SEQUENCE:

    KILL the wpa-supplicant process (that's sustaining the client conn) this way:

kill -2 $( cat /run/wpa_supplicant.wlan0.pid )

sleep 1

kill -9 $( cat /run/wpa_supplicant.wlan0.pid )

FLUSH the WLAN IP setup, using:

ip addr flush dev wlan0

ADD the new host IP ADDRESS, using:

ip addr add 10.1.1.1/24 dev wlan0

START hostapd, which will also put wlan0 UP:

/usr/sbin/hostapd /etc/hostapd/hostapd.conf &

START isc-dhcp-server ( WLAN is up, as host now ):

sudo service isc-dhcp-server restart

    THEN the Access Point should be UP and ready to accept clients.

    Those are my addresses of course / edit to suit your need.

    TWO MORE TIPS: Config files hostapd.conf and dhcp.conf can drive you mad also: -here are working samples. IMPORTANT: do not sweat the 'drivername' in hostapd.conf: it's not needed. 'Commented out' is fine:

    hostapd.conf

    interface=wlan0

    #driver=brcmfmac

    ssid=THIS-IS-MY-AP

    country_code=US

    hw_mode=g

    channel=6

    macaddr_acl=0

    auth_algs=1

    ignore_broadcast_ssid=0

    wpa=2

    wpa_passphrase=12345678

    wpa_key_mgmt=WPA-PSK

    wpa_pairwise=CCMP

    wpa_group_rekey=86400

    ieee80211n=1

    wme_enabled=1

    dhcpd.conf

    COMMENT OUT BOTH OF THE TEMPLATES' 'option domain..' lines.. then ADD THIS AT BOTTOM:

    subnet 10.1.1.0 netmask 255.255.255.0 { range 10.1.1.100 10.1.1.109; option broadcast-address 10.1.1.255; option routers 10.1.1.1; default-lease-time 600; max-lease-time 7200; option domain-name "mynetwork.org"; option domain-name-servers 8.8.8.8, 8.8.4.4; }

    Though this work on Pi it was on DietPi which is straight Debian, so this same advice should suit many Linuxes, including Ububtus of many flavours.

    GOOD LUCK ALL

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