Centos – ntpd error: unable to bind to wildcard address 0.0.0.0 – another process may be running – EXITING

centosiptablesntpd

I have a problem.
Time on server not synchronized.
And it seems that this problem was appear after I set my rules for iptables, which I described here May be I'm wrong and these two events are not related…

CentOS 7.1
ntpd 4.2.6p5

/var/log/messages 

May 25 16:48:49 CentOS-70-64-minimal ntpd[26771]: ntpd 4.2.6p5@1.2349-o Sat Dec 20 02:38:09 UTC 2014 (1)
May 25 16:48:49 CentOS-70-64-minimal ntpd[26771]: proto: precision = 0.046 usec
May 25 16:48:49 CentOS-70-64-minimal ntpd[26771]: 0.0.0.0 c01d 0d kern kernel time sync enabled
May 25 16:48:49 CentOS-70-64-minimal ntpd[26771]: unable to bind to wildcard address 0.0.0.0 - another process may be running - EXITING

ntp.conf 

driftfile /var/lib/ntp/drift
restrict default nomodify notrap nopeer noquery
restrict 127.0.0.1 
restrict ::1
includefile /etc/ntp/crypto/pw
keys /etc/ntp/keys
disable monitor
server ntp1.hetzner.de iburst
server ntp2.hetzner.com iburst
server ntp3.hetzner.net iburst

EDIT
netstat -lanp | grep ':123'

udp        0      0 5.9.152.9:123           0.0.0.0:*                           24483/ntpd          
udp        0      0 127.0.0.1:123           0.0.0.0:*                           24483/ntpd          
udp        0      0 0.0.0.0:123             0.0.0.0:*                           24483/ntpd          
udp6       0      0 2a01:4f8:190:4008:::123 :::*                                24483/ntpd          
udp6       0      0 fe80::3285:a9ff:fee:123 :::*                                24483/ntpd          
udp6       0      0 ::1:123                 :::*                                24483/ntpd          
udp6       0      0 :::123                  :::*                                24483/ntpd

EDIT 2

This problem became more shadow for me…

service ntpd status

Redirecting to /bin/systemctl status  ntpd.service
ntpd.service - Network Time Service
   Loaded: loaded (/usr/lib/systemd/system/ntpd.service; disabled)
   Active: inactive (dead)

systemctl list-unit-files | grep 'ntp' 

ntpd.service                            disabled
ntpdate.service                         disabled

netstat -nlap | grep 'ntpd' 

udp        0      0 5.9.152.9:123           0.0.0.0:*                           3588/ntpd           
udp        0      0 127.0.0.1:123           0.0.0.0:*                           3588/ntpd           
udp        0      0 0.0.0.0:123             0.0.0.0:*                           3588/ntpd           
udp6       0      0 2a01:4f8:190:4008:::123 :::*                                3588/ntpd           
udp6       0      0 fe80::3285:a9ff:fee:123 :::*                                3588/ntpd           
udp6       0      0 ::1:123                 :::*                                3588/ntpd           
udp6       0      0 :::123                  :::*                                3588/ntpd           
unix  2      [ ]         DGRAM                    34224    3588/ntpd

How it can listen port if ntpd disabled….

Best Answer

Based on information you provided (specifically the output of the first EDIT: "netstat -lanp | grep ':123'" and second EDIT: "netstat -nlap | grep 'ntpd'"), it's clear that:

  • at the time of the first edit:

    • your system were running a process with PID 24483;
    • such process declared itself as named "ntpd";
    • such process bound to UDP port 123 for several IPv4 and IPv6 addresses;

  • at the time of the second edit:

    • your system were running a process with PID 3588;
    • such process declared itself as named "ntpd";
    • such process bound to UDP port 123 for several IPv4 and IPv6 addresses;

Under normal conditions (like the ones I'm confident you're experiencing) this means that you are already running an "ntpd" process, and as one ntpd is already running, you cannot launch a new one (or, better, if you launch a new ntpd instance, it will refuse to start simply 'cause it will be unable to get control of needed resources (UDP port 123)).

So, as a general rule, before launching a new "ntpd", please ensure that no other instance is running (...by executing suggested ss/netstat commands and checking results).

As for your final comment -- "How it can listen port if ntpd disabled" -- please note that running/not-running and enabled/disabled are two very distinct concepts and:

  • it's perfectly possible to have running processes that are not boot-enabled (...tipically 'cause you launched them manually, after the boot finished its initial running sequence);

  • it's perfectly possible that a process/service, scheduled to be boot-enabled (and, as such, tipically lanched during the boot-sequence) is not running (...tipically 'cause you have manually stopped it after the boot or it stopped by itself for a plenty of reasons).

So, back to your (not-very-explicit) question:

  • you're unable to launch ntpd 'cause it's already running;

  • if you want to launch it again, please ensure to stop it before;

  • if you want/don't_want it to be launched at boot-time, please ensure it's "enabled"/"disabled" (according to your distribution-specific approach);

  • if you're having problems keeping your time "in-sync", please provide as much details as possible regarding your "ntpd" process (grep ntpd /var/log/messages , as a first start) and the firewall configuration you mentioned to have been applied/changed.

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