Can I get ip address inside my docker container?

How to get container ip address inside this container?

'docker inspect $hostname ...' not suitable, because I don't share /var/run/docker.sock host file to container.

Answers


As the IP address is in the first line of /etc/hosts, you can do in a container the awk command that prints the first word of the first line of /etc/hosts

gg@805689be5f47:/$ awk 'END{print $1}' /etc/hosts 172.17.0.14


I can find the IP address with

hostname -i

Of course, that may not be completely accurate if there is more than one interface.

Edit

Note: According to the hostname man page, hostname -i uses DNS to resolve the ip address, where hostname -I displays all the addresses except loopback, does not depend on DNS, and is recommended.

In all my Docker containers, -i and -I return the same results (but this is not the case on my desktop).


Why not something as simple as:

grep "`hostname`" /etc/hosts|awk '{print $1}'

or

grep "$HOSTNAME" /etc/hosts|awk '{print $1}'

Normally you can use the linux program ifconfig to get IP addresses and other networking details. Your container may not have it, in which case you'll need to install it via apt-get or yum or your distro's package manager. A basic pipeline to get the IP address would be

ifconfig eth0 | grep "inet addr:" | cut -d : -f 2 | cut -d " " -f 1

I found solution to my problem:

/sbin/ip route|awk '/scope/ { print $9 }'

It's print something like: '172.17.0.135'


If you prefer to use ip rather than ifconfig, on Linux you can do:

ip addr | grep inet | tr -s ' ' | cut -d ' ' -f 3

This simply gets all of the IP addresses and interfaces, searches only for those starting with inet and returns only the 3rd column.

As a nice side-effect, this includes the subnet mask, too! (e.g. 172.17.0.2/16)

If you don't want the subnet mask, you can use:

ip addr | grep inet | tr -s ' ' | cut -d ' ' -f 3 | tr -d '/'

NOTE: This shows ALL of the IPs in the container. You can use awk or sed to remove 127.0.0.1/16 and other unwanted IPs. :)


This may work on some containers if it has the "hostname" command.

docker ps to get the (container id)

docker exec -it (container id) hostname -i


You could also look for a line in /etc/hosts that ends with a container id and print the first field:

sed -n 's/^\([0-9\.]*\)[[:blank:]]*[0-9a-f]\{12,\}$/\1/p' /etc/hosts

I'd use awk, but standard awk in dedian:jessie doesn't support regex quantifiers like {12,}.


FROM alpine

# Upgrade grep so that it supports -Po flags
RUN apk add --no-cache --upgrade grep

ENV IPADDRESS "ip a show eth0 | grep -Po 'inet \K[\d.]+'"

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