Browsing articles tagged with "ntpd - Admins Goodies"
Apr 10, 2012
tom

How to configure ntpd to sync time more frequently?

I need to set ntpd to sync time as often as possible, how to do that? Asked by user626528 The iburst option does several checks quickly as soon as the daemon is started and whenever the server is unreachable if you have that in your configuration. The burst option does several checks quickly whenever the server is reachable. By default ntpd then follows an exponential backoff where the time between checks progressively increases, starting at […]

Continue Reading »
Jan 5, 2012
tom

ntpd running as non-root, but outgoing packets match as uid 0

I set my default iptables OUTPUT chain to DROP packets. I then created a firewall rule to only allow the ntp user to send ntp packets out: iptables -A OUTPUT -m owner –uid-owner ntp -p udp –dport 123 -j ACCEPT However, every 10-20 minutes I would see: ntpd[27769]: sendto(<snip>) (fd=22): Operation not permitted I then removed the -m owner –uid-owner ntp portion of the rule and added a log rule before it: iptables -A OUTPUT […]

Continue Reading »
Nov 18, 2011
tom

NTP doesn’t sync

I’m using Meinberg NTP to sync the time in a VPS. The clock refuses to sync – there’s a ~30s shift comparing to other servers. Also ntpq -p is continuously showing zeros for reach, delays and jitters, which means something’s wrong… Actions I’ve taken which didn’t help: Restarted the NTP service using a script that comes with Meinberg NTP Added port 123 for UDP and TCP as an exception port to Windows Firewall Added Meinberk […]

Continue Reading »
Nov 10, 2011
tom

How to override the ntp information sent by dhcp in debian?

I have a server in a network receiving all its network information from DHCP. The problem is that the ntp-server being sent is not set to UTC. I want to use the configuration for ntp found in /etc/ntp.conf but the DHCP information takes precedence. How can I force ntpd to use the configuration in /etc/ntp.conf as opposed to the one sent by DHCP? What is the Debian way to do this? I suggest you edit/create […]

Continue Reading »
Oct 27, 2011
tom

How to synchronize time between a Windows client and a Linux NTP server?

I want my Windows 7 machine to get its time from my Linux Debian Sid server. So I want ahead and installed OpenNTPD from the Debian repository. It doesn’t listen to anything by default, so I configured it as follows: listen on 192.168.0.1 server 0.debian.pool.ntp.org server 1.debian.pool.ntp.org server 2.debian.pool.ntp.org server 3.debian.pool.ntp.org 192.168.0.1 being my server’s IP address on my LAN. I entered it in the Windows settings and I got this: I used a network […]

Continue Reading »
Oct 25, 2011
tom

Server Time is *WAY* Off

The time on my server is about 19 hours behind and I cannot for the life of me figure out how to synchronize it. I did follow the steps here, and this is the output: [root@ip-72-167-39-231 ~]# /sbin/service ntpd stop Shutting down ntpd: [ OK ] [root@ip-72-167-39-231 ~]# /usr/sbin/ntpdate 0.pool.ntp.org 25 Oct 08:42:32 ntpdate[22173]: adjust time server 199.4.29.166 offset 0.034126 sec [root@ip-72-167-39-231 ~]# clock Mon 24 Oct 2011 01:43:18 PM MST -0.344112 seconds [root@ip-72-167-39-231 ~]# […]

Continue Reading »
Aug 29, 2011
tom

NTP fudge network source stratum

Is it possible to configure ntpd to fudge the stratum level of a network source? Upon first glance, I thought the fudge directive could accomplish this, however after browsing the ntp.conf(5) man pages, I found this directive only applies to Reference Clocks. A few details: I have a local server running ntpd as the primary time source for clients on the LAN. This server is pointed at the ntp.org pool, and usually maintains a stratum […]

Continue Reading »
Aug 24, 2011
tom

Compare NTPD and ntpdate

What are the pros and cons between these two ways to synchronize your server? It seems to me that your server would probably not drift more than 1 second every day, so ntpdate on a crontab would be ok. But I heard you could use redundant NTP servers here http://www.pool.ntp.org/en/use.html in order to maintain synchronized time in case of failure. Do you have any suggestions? The NTP algorithm includes information to allow you to calculate […]

Continue Reading »
Aug 22, 2011
tom

Building a local time server

I am trying to install a time server on a local Ubuntu machine, so other servers in my network would sync with it. We have decided to install our own time server, rather than letting each server update from an external server, to minimize the security risk. Any ideas what’s the best server to install? Are there any known security issues? Where should the server update from? Is there a well-trusted time server out there? […]

Continue Reading »
Aug 22, 2011
tom

Security issues with NTPD

I want to sync some two dozen Linux servers which are spread all over the world. I was thinking about using NTPD, but I want to know the security implications of using it: Is there a possible vulnerability? Should I sync them to a local server and sync it manually? Thanks, Udi any piece of network software is a potential vulnerability, especially if it runs as root as ntpd does. That said, ntpd has a […]

Continue Reading »
Pages:1234»