commands in cexec:v1.0.0 cannot resolve host, but image2disk:v1.0.0 can

[nicolacdnll]

Commands within cexec:v1.0.0 cannot resolve host, but image2disk:v1.0.0 can download files from the same host and path. The example below is with curl but the same happens with a yum install.

          version: "0.1"
          name: centos7
          global_timeout: 1800
          tasks:
            - name: os-installation
              worker: '{{.device_1}}'
              volumes:
                - "/dev:/dev"
                - "/dev/console:/dev/console"
                - "/lib/firmware:/lib/firmware:ro"
              actions:
                - name: "stream-os-image"
                  image: "image2disk:v1.0.0"
                  timeout: 600
                  environment:
                    DEST_DISK: /dev/sda
                    IMG_URL: https://foo.bar.com/filea.raw.gz
                    COMPRESSED: true
[... other actions ...]
                - name: "download-file"
                  image: cexec:v1.0.0
                  timeout: 90
                  environment:
                    BLOCK_DEVICE: /dev/sda4
                    FS_TYPE: xfs
                    CHROOT: y
                    DEFAULT_INTERPRETER: "/bin/sh -c"
                    CMD_LINE: "curl https://foo.bar.com/fileb.img -o /path/fileb.img"

Expected Behaviour

To be able to curl the file like in this example: https://docs.tinkerbell.org/deploying-operating-systems/examples-rhel-centos/ Am I doing something wrong?

Current Behaviour

curl: (6) Could not resolve host: foo.bar.com.
FATA[0011] Error running [/bin/bash [-c curl curl https://foo.bar.com/fileb.img -o /path/fileb.img]] [exit status 6]`

Your Environment

Linuxkit: https://github.com/linuxkit/linuxkit

[Cajga]

@nicolacdnll, we run into the same. Have you managed to find a workaround?

[Cajga]

ok so basically an echo 'nameserver IPOFYOURDNSSERVER' > /etc/resolv.conf workarounds this problem...

[jacobweinstock]

Wow, sincere apologies for the extremely delayed response here.

This is a symptom of chroot not handling networking/dns/etc and this action not taking those things into account. Let me see if i can figure out an OS agnostic way to get networking and DNS working. Maybe bind mounts or similar. Will try some things out and report back. Thanks for your patience !

[rpardini]

This indeed depends on the image being deployed. If it uses systemd-resolved, then /etc/resolv.conf will be a dangling symlink (to some /run/... file put there by systemd when the image is really booted into, but not under chroot-exec).
To make it work during provisioning, move /etc/resolv.conf (which is a dangling symlink) away, replace it with a real resolv.conf (nameserver …) one. Then bring the symlink back at the end of the workflow, so it works again when provisioning is finished...