Environment variables from legacy containers links have disappeared with docker 29.0 #6666
Description
Description
Environment variables created by docker when using legacy containers links disappeared with docker 29.0: https://docs.docker.com/engine/network/links/#environment-variables
Reproduce
- docker run --rm --name container1 -p 1234 -d ubuntu sleep infinity > /dev/null
- docker run --rm --name container2 --link container1 ubuntu env
cleanup:
- docker stop container1 --timeout 0 > /dev/null
Expected behavior
CONTAINER1_PORT should exist in step 2, as well as other CONTAINER1_* environment variables:
docker 28.5.1: (5:28.5.2-1~ubuntu.22.04~jammy)
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=aa0dd55feb85
CONTAINER1_PORT=tcp://172.17.0.2:1234
CONTAINER1_PORT_1234_TCP=tcp://172.17.0.2:1234
CONTAINER1_PORT_1234_TCP_ADDR=172.17.0.2
CONTAINER1_PORT_1234_TCP_PORT=1234
CONTAINER1_PORT_1234_TCP_PROTO=tcp
CONTAINER1_NAME=/container2/container1
HOME=/root
docker 29.0.2: (5:29.0.2-1~ubuntu.22.04~jammy)
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=d2d80ab01a89
HOME=/root
tested on ubuntu 22.04 and 24.04 with the docker apt repository
docker version
Client: Docker Engine - Community
Version: 29.0.2
API version: 1.52
Go version: go1.25.4
Git commit: 8108357
Built: Mon Nov 17 12:33:14 2025
OS/Arch: linux/amd64
Context: default
Server: Docker Engine - Community
Engine:
Version: 29.0.2
API version: 1.52 (minimum version 1.44)
Go version: go1.25.4
Git commit: e9ff10b
Built: Mon Nov 17 12:33:14 2025
OS/Arch: linux/amd64
Experimental: false
containerd:
Version: v2.1.5
GitCommit: fcd43222d6b07379a4be9786bda52438f0dd16a1
runc:
Version: 1.3.3
GitCommit: v1.3.3-0-gd842d771
docker-init:
Version: 0.19.0
GitCommit: de40ad0docker info
Client: Docker Engine - Community
Version: 29.0.2
Context: default
Debug Mode: false
Plugins:
buildx: Docker Buildx (Docker Inc.)
Version: v0.30.0
Path: /usr/libexec/docker/cli-plugins/docker-buildx
compose: Docker Compose (Docker Inc.)
Version: v2.40.3
Path: /usr/libexec/docker/cli-plugins/docker-compose
Server:
Containers: 18
Running: 6
Paused: 0
Stopped: 12
Images: 137
Server Version: 29.0.2
Storage Driver: overlay2
Backing Filesystem: extfs
Supports d_type: true
Using metacopy: false
Native Overlay Diff: true
userxattr: false
Logging Driver: json-file
Cgroup Driver: systemd
Cgroup Version: 2
Plugins:
Volume: local
Network: bridge host ipvlan macvlan null overlay
Log: awslogs fluentd gcplogs gelf journald json-file local splunk syslog
CDI spec directories:
/etc/cdi
/var/run/cdi
Discovered Devices:
cdi: nvidia.com/gpu=0
cdi: nvidia.com/gpu=GPU-xxx
cdi: nvidia.com/gpu=all
Swarm: inactive
Runtimes: runc io.containerd.runc.v2 nvidia
Default Runtime: runc
Init Binary: docker-init
containerd version: fcd43222d6b07379a4be9786bda52438f0dd16a1
runc version: v1.3.3-0-gd842d771
init version: de40ad0
Security Options:
apparmor
seccomp
Profile: builtin
cgroupns
Kernel Version: 6.8.0-87-generic
Operating System: Ubuntu 22.04.5 LTS
OSType: linux
Architecture: x86_64
CPUs: 16
Total Memory: xxxGiB
Name: xxx
ID: xxx
Docker Root Dir: /var/lib/docker
Debug Mode: false
Username: xxx
Experimental: false
Insecure Registries:
nuc:5000
::1/128
127.0.0.0/8
Live Restore Enabled: false
Firewall Backend: iptablesAdditional Info
I understand the --link flag is a legacy feature, but the documentation only says it "may eventually be removed", and I didn't find any mention of changes on this documentation or the docker engine v29 release blog.