NoBIGTech Wiki Técnico

Tired of having to install ping/curl/telnet/netcat to test connectivity on docker containers to other hosts? This is probably the most useful thing i've learn on container technologies

container_name=your-example-container
 
# Get the PID of docker container main command
docker inspect -f '{{.State.Pid}}' $container_name
 
# Execute whatever command you want (you must have it installed on host)
#  example:
nsenter -t PID -n host techdoku.nogafam.es
nsenter -t PID -n telnet 2.3.4.5 80
nsenter -t PID -n iptables -A OUTPUT -d 1.2.3.4 -p udp --dport 53 -j ACCEPT 
nsenter -t PID -n netstat -lptuan
# or whatever network-related command you want to exec

Keep in mind this won't execute commands on the container, so things like for example querying /etc/resolv.conf file WON'T WORK

cat /etc/resolv.conf

Technically, network namespaces are a technology on *nix operating systems that allows to create separated or/and isolated network stacks on the hosts, which contains it's own private set of IP addresses, it's own routing table, socket listing, connection tracking table, firewall, and other network-related resources… source on WikiPedia