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DHCP 在网络准备就绪之前启动

tag-icon • tag-icon debian bash dhcp isc-dhcp networkmanager
DHCP 在网络准备就绪之前启动

我的 DHCP 服务器出了问题。重启后 isc-dhcp-server 无法就绪，因为网络（它使用 NetworkManager）尚未就绪。

我在 isc-dhcp-server 启动脚本中放置了一个睡眠命令，但是当服务器重新启动时，脚本删除了包含睡眠命令的行。

当网络准备就绪时，如何延迟 DHCP 启动或重新启动？以下是一些信息：

Linux 版本

PRETTY_NAME="Debian GNU/Linux 11 (bullseye)"
NAME="Debian GNU/Linux"
VERSION_ID="11"
VERSION="11 (bullseye)"

日志控制

jan 09 07:50:22 server systemd[1]: Starting LSB: DHCP server...
jan 09 07:50:28 server isc-dhcp-server[579]: Launching IPv4 server only.
jan 09 07:50:30 server dhcpd[622]: WARNING: Host declarations are global.  They are not limited to the scope you declared them in.
jan 09 07:50:30 server dhcpd[632]: WARNING: Host declarations are global.  They are not limited to the scope you declared them in.
jan 09 07:50:31 server dhcpd[632]: Wrote 0 deleted host decls to leases file.
jan 09 07:50:31 server dhcpd[632]: Wrote 0 new dynamic host decls to leases file.
jan 09 07:50:31 server dhcpd[632]: Wrote 79 leases to leases file.
jan 09 07:50:31 server dhcpd[632]: 
jan 09 07:50:31 server dhcpd[632]: No subnet declaration for enp32s0 (no IPv4 addresses).
jan 09 07:50:31 server dhcpd[632]: ** Ignoring requests on enp32s0.  If this is not what
jan 09 07:50:31 server dhcpd[632]:    you want, please write a subnet declaration
jan 09 07:50:31 server dhcpd[632]:    in your dhcpd.conf file for the network segment
jan 09 07:50:31 server dhcpd[632]:    to which interface enp32s0 is attached. **
jan 09 07:50:31 server dhcpd[632]: 
jan 09 07:50:31 server dhcpd[632]: 
jan 09 07:50:31 server dhcpd[632]: Not configured to listen on any interfaces!
jan 09 07:50:31 server dhcpd[632]: 
jan 09 07:50:31 server dhcpd[632]: If you think you have received this message due to a bug rather
jan 09 07:50:31 server dhcpd[632]: than a configuration issue please read the section on submitting
jan 09 07:50:31 server dhcpd[632]: bugs on either our web page at www.isc.org or in the README file
jan 09 07:50:31 server dhcpd[632]: before submitting a bug.  These pages explain the proper
jan 09 07:50:31 server dhcpd[632]: process and the information we find helpful for debugging.
jan 09 07:50:31 server dhcpd[632]: 
jan 09 07:50:31 server dhcpd[632]: exiting.
jan 09 07:50:33 server isc-dhcp-server[579]: Starting ISC DHCPv4 server: dhcpdcheck syslog for diagnostics. ...
jan 09 07:50:33 server isc-dhcp-server[640]:  failed!
jan 09 07:50:33 server isc-dhcp-server[641]:  failed!
jan 09 07:50:33 server systemd[1]: isc-dhcp-server.service: Control process exited, code=exited, status=1/FAILURE
jan 09 07:50:33 server systemd[1]: isc-dhcp-server.service: Failed with result 'exit-code'.
jan 09 07:50:33 server systemd[1]: Failed to start LSB: DHCP server.

#> cat /etc/network/interfaces

# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

source /etc/network/interfaces.d/*

# The loopback network interface
auto lo
iface lo inet loopback

#> cat /etc/dhcp/dhcpd.conf

# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#

option domain-name "server.local";
option domain-name-servers 8.8.8.8, 8.8.4.4;

default-lease-time 600;
max-lease-time 7200;

ddns-update-style none;

authoritative;


subnet 192.168.1.0 netmask 255.255.255.0 {
        # — default gateway
        option routers 192.168.1.3;
        option subnet-mask 255.255.255.0;
        #option nis-domain "SERVER";
        option domain-name "SERVER";
        # Cloudflare
        option domain-name-servers 1.1.1.1, 1.0.0.1;
        option time-offset -18000;
        option ntp-servers 192.168.1.3;
        #option tftp-server-name "192.168.1.10";
        option broadcast-address 192.168.1.255;
        range 192.168.1.11 192.168.1.90;
        default-lease-time 21600;
        max-lease-time 43200;
        # Fixed IP addresses can also be specified for hosts.
    [...]

感谢你们。

答案1

要在网络启动后启动服务，请After=network-online.target在 systemd 服务文件中进行设置。

不要使用After=NetworkManager-wait-online.service，因为那是一个实现细节。ordersNetworkManager-wait-online.service本身Before=network-online.target，因此您可以隐式地获得该顺序。

例如，通过 进行操作systemctl edit isc-dhcp-server.service。

阅读手册页，特别是关于ipv4.may-fail=no如何ipv4.required-timeout告诉 NetworkManager 该接口仅准备好使用 IPv4 地址。

一个更好、更强大的解决方案可能是说服 DHCP 服务器在地址尚未出现时动态地应对启动。

答案2

您可以尝试做的是

systemctl enable systemd-networkd.service systemd-networkd-wait-online.service

进而

[Unit]
After=systemd-networkd-wait-online.service
Wants=systemd-networkd-wait-online.service

来源 https://stackoverflow.com/questions/35805354/systemd-start-service-at-boot-time-after-network-is-really-up-for-wol-purpose

/etc/systemd/system/我通常直接用 vi 或 nano编辑文件

然后执行 systemctl daemon-reload 并重新启动（如果服务正常启动）

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