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[Solution] Use more than a dozen lines of scripts to execute commands in the container network namespace and to execute host space commands

Popularity：813 ℃/2025-03-12 12:46:53

Use more than a dozen lines of scripts to execute commands in the container network namespace and to execute host space commands

Usually there is no in the containernetstat tcpdumpNamed, evenipNone.
When you need to troubleshoot network problems in the container, you can only temporarily download these commands, which is a waste of time to operate.

Generally speaking, there are more commands carried by the host, so the host's commands can be used to observe the network status in the container.

  • Use docker inspect to find the namespace path of the container
  • Use the ip command to switch namespaces and execute commands

ip netns can only recognize namespaces in /var/run/netns

#!/bin/bash
container_name=${@:1:1}
command=${@:2}

if [ -z "$container_name" ]; then
    echo "Usage: $0 <container_name> <command>"
    exit 1
fi

if [ -z "$command" ]; then
    echo "Usage: $0 <container_name> <command>"
    exit 1
fi

exec_inside_container() {
    set -e
    sandbox_key=$(docker inspect $container_name --format '{{ . }}')
    netns_name=$1-$(basename $sandbox_key)
    set +e

    rm -f /var/run/netns/$netns_name
    ln -s $sandbox_key /var/run/netns/$netns_name

    ip netns exec $netns_name $command
    rm -f /var/run/netns/$netns_name
}

exec_inside_container $container_name $command

How to use: View network card information in the container in the host

$ ./ ubuntu ip a
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
1116: eth0@if1117: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default 
    link/ether 02:42:ac:11:00:02 brd ff:ff:ff:ff:ff:ff link-netnsid 0
    inet 172.17.0.2/16 brd 172.17.255.255 scope global eth0
       valid_lft forever preferred_lft forever
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