rkt attach

Applications can be started in interactive mode and later attached via rkt attach.

In order for an application to be attachable:

  • it must be started in interactive mode
  • it must be running as part of a running pod
  • it must support the corresponding attach mode

To start an application in interactive mode, either tty or stream must be passed as value for the --stdin, --stdout and --stderr options.

An application can be run with a dedicated terminal and later attached to:

# rkt run quay.io/coreos/alpine-sh --stdin tty --stdout tty --stderr tty
# rkt attach --mode tty ${UUID}

/ # hostname
rkt-911afe8e-992f-4089-8666-4a4c957a1964

/ # tty     
/rkt/iottymux/alpine-sh/pts
^C

In a similar way, an application can be run without a tty but with separated attachable streams:

# rkt run quay.io/coreos/alpine-sh --stdin stream --stdout stream --stderr stream
# rkt attach --mode stdin,stdout,stderr ${UUID}
hostname
rkt-846c35db-6728-471a-ad50-66d3a8d7ff9c

tty
not a tty
^C

If a pod contains multiple applications, the one to be used as attach target can be specified via --app.

The following options are allowed as --mode values:

  • list: list available endpoints, and return early without attaching
  • auto: attach to all available endpoints
  • tty: bi-directionally attach to the application terminal
  • tty-in or tty-out: uni-directionally attach to the application terminal
  • stdin,stdout,stderr: attach to specific application streams. Omitted streams will no be attached

A more complex example, showing the usage of advanced options and piping:

# rkt run quay.io/coreos/alpine-sh --stdin stream --stdout stream --stderr stream
# rkt attach --app alpine-sh --mode list 846c35db
stdin
stdout
stderr

# echo 'hostname; fakecmd' | ./rkt attach --app alpine-sh --mode auto ${UUID}
rkt-846c35db-6728-471a-ad50-66d3a8d7ff9c
/bin/sh: fakecmd: not found
^C

# echo 'hostname; fakecmd' | ./rkt attach --app alpine-sh --mode stdin,stdout ${UUID}
rkt-846c35db-6728-471a-ad50-66d3a8d7ff9c
^C

# echo 'hostname; fakecmd' | ./rkt attach --app alpine-sh --mode stdin,stderr ${UUID}
/bin/sh: fakecmd: not found
^C

Options

Flag Default Options Description
--app `` Name of an application Name of the app to attach to within the specified pod
--mode auto "list", "auto" or tty/stream mode Attaching mode

Global options

See the table with global options in general commands documentation.