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如何延迟 Upstart 的网络设备启动信号直到满足条件？

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如何延迟 Upstart 的网络设备启动信号直到满足条件？

我需要等待特定条件满足后网络接口才被视为“启动”。Upstartnet-device-up在满足此条件之前发送信号，这会导致依赖此条件的脚本失败。如何延迟 Upstart 的 net-device-up 信号直到条件满足？

答案1

一种解决方案是放入一个脚本，/etc/network/if-up.d/该脚本在任何其他 if-up.d 脚本之前执行，并等待特定条件满足或发生超时。例如，这是一个脚本，用于等待使用“自动”方法配置的 IPv6 接口上的非链路本地 IPv6 地址：

#!/bin/sh

LOG_FILE="/tmp/autoipv6.log"

if [ "$ADDRFAM" = "inet6" -a "$METHOD" = "auto" ]; then
        echo "Auto method detected, waiting for IP address" >> $LOG_FILE

        #wait until we have an IP address, or a timeout occurs
        TIMEOUT=50 #5 second timeout--each iteration sleeps for 1/10th of a second
        #get the number of addresses, excluding link-local addresses
        ADDRESS_COUNT=`ip addr show dev eth0 | grep inet6 | grep -v fe80 | wc -l`

        until [ $TIMEOUT -eq 0 ]; do
                NEW_ADDRESS_COUNT=`ip addr show dev eth0 | grep inet6 | grep -v fe80 | wc -l`

                # break out of the loop if more IPv6 addresses have been assigned
                # this is implementation is naive: no guarantee is given that the new addresses
                # are the result of the autoconfiguration request
                if [ "$NEW_ADDRESS_COUNT" -gt "$ADDRESS_COUNT" ]; then
                        echo "Detected new IP address, exiting" >> $LOG_FILE
                        ifconfig >> $LOG_FILE
                        exit 0;
                fi

                TIMEOUT=$((TIMEOUT-1))
                sleep .1
        done

        echo "Timeout waiting for IP address" >> $LOG_FILE
        exit 1;
fi

这个“等待条件”脚本的运行很重要前if-up.d Upstart 脚本运行（Upstart if-up.d 脚本是net-device-up生成信号的地方）。 if-up.d 脚本由以下脚本执行：运行部件按词汇排序顺序（与 ls 命令的默认输出顺序相同），因此保证顺序的一个简单技巧是将脚本命名为“000wait-for-condition”。

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