userdoc:guest_lxc_container_command [AstLinux Documentation]

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====== Command via a Container ======

There are occasions where a command might be useful within AstLinux, but it may use python, golang, etc. or is just large in comparison to the 50 MB size of the AstLinux image.  A LXC container can be a handy tool to add such a command.

**Resource Usage:** (minimum)
  * Memory: 100 MB
  * Storage: 0.4 GB
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Below is an example how to add the ''lynx'' command line web browser.  The ''lynx'' container only runs when needed.

First, it is assumed the ''lxcbr0'' interface is setup per the **[[userdoc:guest_lxc_container#quick_start_guide|Quick Start Guide]]** -> Enable LXC Support.

Then from the CLI:

  lxc-create -t download -n lynx -- -d debian -r buster -a amd64 --no-validate

  service lxc restart

  lxc-attach lynx
    apt update
    apt install lynx ca-certificates fping
    exit

Next, stop the ''lynx'' container and keep it from automatically starting.

  lxc-stop lynx
  sed -i 's/^lxc.start.auto=1/lxc.start.auto=0/' /var/lib/lxc/lynx/config

Finally, create a wrapper script to start/stop the container and issue a command.

Place this script at ''/mnt/kd/bin/lynx'' and give it ''chmod 755'' permissions.
  #!/bin/sh
  ##
  ## lynx wrapper for LXC Debian 10 container
  ##
  
  ## generate a random uid
  rand_uid=$((RANDOM % 4999 + 95000))
  
  ## Destination IP to test when container network is active
  ping_ip="8.8.4.4"
  
  trap 'printf "Abort\n" >&2; lxc-stop lynx; exit 1' INT TERM EXIT
  
  lxc-start lynx
  
  printf "Waiting for container network to become active... "
  lxc-attach lynx -u $rand_uid -- fping -q -r15 $ping_ip
  printf "OK\n"
  
  lxc-attach lynx -u $rand_uid -- lynx "$@"
  
  lxc-stop lynx
  
  trap - INT TERM EXIT
  
  exit 0

!!Tip ->!! If you edit ''/var/lib/lxc/lynx/config'' and assign a manual IP address, the container starts very quickly, whereas using DHCP it takes 4-6 seconds to establish the network.

Test it!

  /mnt/kd/bin/lynx https://www.astlinux-project.org

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!!Related Info ->!! **[[userdoc:guest_lxc_container|LXC container in AstLinux]]**