Why do some of the network services fail at boot time but work once Red Hat Enterprise Linux system

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本文介绍了解决Red Hat Enterprise Linux系统中网络依赖服务启动失败的问题。通过在/etc/sysconfig/network文件中设置NETWORKDELAY参数，可以引入延迟，确保所有网络服务在系统启动时能正确初始化。文章详细解释了如何调整该参数以找到最佳延迟值。

https://access.redhat.com/solutions/7336

SOLUTION 已验证 - 已更新 2019年四月5日08:56 -

English

环境

Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 5
Red Hat Enterprise Linux 4
initscripts(/etc/init.d/network)

问题

Some services that require network connectivity do not start properly during system boot, but they can be started manually once the system is up and running.
NIS service does not start at boot. Once the server is up and running, the NIS service can be started with out any issues. /var/log/messages shows the following error messages at boot time:

Raw
```
Jul 27 08:37:33 server1 ypbind: Host name lookup failure
Jul 27 08:38:27 server1 ypbind[8554]: broadcast: RPC: Timed out.
```

决议

A workaround for these issues is to introduce a delay at the end of the start function in the network init script , Using the NETWORKDELAY global parameter.

To do that, edit the /etc/sysconfig/network file and add the following:

Raw

NETWORKDELAY=60

Start with a high delay of 60 seconds. If this solves the problem, then progressively lower the value until the lowest value at which all network services continue to start is found (This will take some testing to find the magic number). For some systems a value as low as 10 will do the trick, for others a higher value may be needed.

Reboot after making this change and take note during the boot process. There should be a long delay when the network service is starting up. After that, other network dependent services such as ntpd and NFS should start normally. The next step will be to experiment with values lower than 60 until the lowest value that continues to allow all network services to start is found.

If you use NetworkManager service, refer Network services start before ethernet devices are up in Red Hat Enterprise Linux.

根源

There are multiple possible causes for this type of issue.

One possibility is the use of Spanning Tree on the network, which could delay network initialization on the system.
Another issue is a known problem with some network cards where networking is "advertised" to the system as being fully started, when in fact it has not. This problem stems from the fact that the network card itself takes an unusually long time to initialize. This results in network dependent services trying to start before the network is ready to accommodate them.