stern / Stern
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stern
Fork of discontinued wercker/stern
Stern allows you to tail multiple pods on Kubernetes and multiple containers
within the pod. Each result is color coded for quicker debugging.
The query is a regular expression so the pod name can easily be filtered and you don't need to specify the exact id (for instance omitting the deployment id). If a pod is deleted it gets removed from tail and if a new pod is added it automatically gets tailed.
When a pod contains multiple containers Stern can tail all of them too without
having to do this manually for each one. Simply specify the container flag to
limit what containers to show. By default all containers are listened to.
Installation
Download binary
Download a binary release
Build from source
go get -u github.com/stern/stern
asdf (Linux/macOS)
If you use asdf, you can install like this:
asdf plugin-add stern
asdf install stern latest
Homebrew (Linux/macOS)
If you use Homebrew, you can install like this:
brew install stern
Usage
stern pod-query [flags]
The pod query is a regular expression so you could provide "web-\w" to tail
web-backend and web-frontend pods but not web-123.
cli flags
| flag | default | purpose |
|---|---|---|
--all-namespaces, -A
|
If present, tail across all namespaces. A specific namespace is ignored even if specified with --namespace. | |
--color |
auto |
Force set color output. auto: colorize if tty attached, always: always colorize, never: never colorize |
--completion |
Outputs stern command-line completion code for the specified shell. Can be 'bash' or 'zsh' | |
--container, -c
|
.* |
Container name when multiple containers in pod (regular expression) |
--container-state |
running |
Tail containers with status in running, waiting or terminated. Default to running. |
--context |
Kubernetes context to use. Default to kubectl config current-context
|
|
--exclude, -e
|
Log lines to exclude; specify multiple with additional --exclude; (regular expression) |
|
--exclude-container, -E
|
Container name to exclude when multiple containers in pod (regular expression) | |
--help, -h
|
Output Usage and Flags details | |
--include, -i
|
Log lines to include; specify multiple with additional --include; (regular expression) |
|
--init-containers |
true |
Include or exclude init containers |
--kubeconfig |
see note | Path to kubeconfig file to use. Default to KUBECONFIG variable then ~/.kube/config path |
--namespace, -n
|
Kubernetes namespace to use. Default to namespace configured in Kubernetes context. To watch multiple namespaces, repeat this flag or set comma-separated value. | |
--output, -o
|
default |
Specify predefined template. Currently support: [default, raw, json] See templates section |
--selector, -l
|
Selector (label query) to filter on. If present, default to .* for the pod-query. |
|
--field-selector |
Selector (field query) to filter on. If present, default to .* for the pod-query. |
|
--since, -s
|
48h |
Return logs newer than a relative duration like 5s, 2m, or 3h. Defaults to 48h. |
--tail |
-1 |
The number of lines from the end of the logs to show. Defaults to -1, showing all logs. |
--template |
Template to use for log lines, leave empty to use --output flag | |
--timestamps, -t
|
Print timestamps | |
--version, -v
|
Print the version and exit |
See stern --help for details
Stern will use the $KUBECONFIG environment variable if set. If both the
environment variable and --kubeconfig flag are passed the cli flag will be
used.
templates
stern supports outputting custom log messages. There are a few predefined
templates which you can use by specifying the --output flag:
| output | description |
|---|---|
default |
Displays the namespace, pod and container, and decorates it with color depending on --color |
raw |
Only outputs the log message itself, useful when your logs are json and you want to pipe them to jq
|
json |
Marshals the log struct to json. Useful for programmatic purposes |
It accepts a custom template through the --template flag, which will be
compiled to a Go template and then used for every log message. This Go template
will receive the following struct:
| property | type | description |
|---|---|---|
Message |
string | The log message itself |
NodeName |
string | The node name where the pod is scheduled on |
Namespace |
string | The namespace of the pod |
PodName |
string | The name of the pod |
ContainerName |
string | The name of the container |
The following functions are available within the template (besides the builtin functions):
| func | arguments | description |
|---|---|---|
json |
object |
Marshal the object and output it as a json text |
color |
color.Color, string |
Wrap the text in color (.ContainerColor and .PodColor provided) |
Examples:
Tail the gateway container running inside of the envvars pod on staging
stern envvars --context staging --container gateway
Tail the staging namespace excluding logs from istio-proxy container
stern -n staging --exclude-container istio-proxy .
Show auth activity from 15min ago with timestamps
stern auth -t --since 15m
Follow the development of some-new-feature in minikube
stern some-new-feature --context minikube
View pods from another namespace
stern kubernetes-dashboard --namespace kube-system
Tail the pods filtered by run=nginx label selector across all namespaces
stern --all-namespaces -l run=nginx
Follow the frontend pods in canary release
stern frontend --selector release=canary
Tail the pods on kind-control-plane node across all namespaces
stern --all-namespaces --field-selector spec.nodeName=kind-control-plane
Pipe the log message to jq:
stern backend -o json | jq .
Only output the log message itself:
stern backend -o raw
Output using a custom template:
stern --template '{{printf "%s (%s/%s/%s/%s)\n" .Message .NodeName .Namespace .PodName .ContainerName}}' backend
Output using a custom template with stern-provided colors:
stern --template '{{.Message}} ({{.Namespace}}/{{color .PodColor .PodName}}/{{color .ContainerColor .ContainerName}}){{"\n"}}' backend
Completion
Stern supports command-line auto completion for bash or zsh. stern --completion=(bash|zsh) outputs the shell completion code which work by being
evaluated in .bashrc, etc for the specified shell. In addition, Stern
supports dynamic completion for --namespace and --context. In order to use
that, kubectl must be installed on your environment.
If you use bash, stern bash completion code depends on the bash-completion. On the macOS, you can install it with homebrew as follows:
# If running Bash 3.2
brew install bash-completion
# or, if running Bash 4.1+
brew install [email protected]
Note that bash-completion must be sourced before sourcing the stern bash
completion code in .bashrc.
source "$(brew --prefix)/etc/profile.d/bash_completion.sh"
source <(stern --completion=bash)
If you use zsh, just source the stern zsh completion code in .zshrc.
source <(stern --completion=zsh)
Running with container
You can also use stern using a container:
docker run ghcr.io/stern/stern --version
If you are using a minikube cluster, you need to run a container as follows:
docker run --rm -v "$HOME/.minikube:$HOME/.minikube" -v "$HOME/.kube:/$HOME/.kube" -e KUBECONFIG="$HOME/.kube/config" ghcr.io/stern/stern .
You can find image tags in https://github.com/orgs/stern/packages/container/package/stern.
Running in Kubernetes Pods
If you want to use stern in Kubernetes Pods, you need to create the following ClusterRole and bind it to ServiceAccount.
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
name: stern
rules:
- apiGroups: [""]
resources: ["pods", "pods/log"]
verbs: ["get", "watch", "list"]
Contributing to this repository
Please see CONTRIBUTING for details.