archive/tar: sockets not supported

[rk0n]

• I'm submitting a ...

  • [X ] bug report
  • feature request
  • support request

• What is the current behavior?
  When trying to backup a gitlab docker volume I get an error and no tar file:

level=error msg="Fatal error running backup: takeBackup: error compressing backup folder: archive/tar: sockets not supported"

• If the current behavior is a bug, please provide the configuration and steps to reproduce and if possible a minimal demo of the problem.

version: '3.6'
services:
  nginx:
    image: nginxproxy/nginx-proxy
    restart: always
    ports:
      - "80:80"
      - "443:443"
    labels:
      - docker-volume-backup.stop-during-backup=true
    volumes:
      - /var/run/docker.sock:/tmp/docker.sock:ro
      - ./data/nginx/certs:/etc/nginx/certs:ro
      - ./data/nginx/vhosts:/etc/nginx/vhost.d
      - ./data/nginx/html:/usr/share/nginx/html
    networks:
      - proxy

  proxy-companion:
    restart: always
    image: sebastienheyd/self-signed-proxy-companion
    labels:
      - docker-volume-backup.stop-during-backup=true
    volumes:
        - /var/run/docker.sock:/var/run/docker.sock:ro
        - ./data/nginx/certs:/etc/nginx/certs:rw
    depends_on:
      - nginx

  gitlab:
    image: 'gitlab/gitlab-ce:14.7.0-ce.0'
    restart: always
    hostname: 'git.localhost'
    shm_size: '256m'
    volumes:
      - ./data/gitlab/config:/etc/gitlab
      - ./data/gitlab/logs:/var/log/gitlab
      - ./data/gitlab/data:/var/opt/gitlab
    environment:
      VIRTUAL_HOST: git.localhost
      VIRTUAL_PORT: 80
      SELF_SIGNED_HOST: git.localhost
      GITLAB_OMNIBUS_CONFIG: |
         external_url 'https://git.localhost'
         nginx['listen_port'] = 80
         nginx['listen_https'] = false
    labels:
      - docker-volume-backup.stop-during-backup=true
    ports:
      - "10022:22"
    networks:
      - proxy

  backup:
    image: offen/docker-volume-backup:v2.10.0
    environment:
      # A backup is taken each day at 3AM
      BACKUP_CRON_EXPRESSION: "0 3 * * *"
      BACKUP_FILENAME: backup-%Y-%m-%dT%H-%M-%S.tar.gz
      BACKUP_RETENTION_DAYS: 7
      GPG_PASSPHRASE: secretkey
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock:ro
      - /etc/timezone:/etc/timezone:ro
      - /etc/localtime:/etc/localtime:ro
      - ./backups:/archive
      - ./:/backup/docker-compose:ro
      - ./data/gitlab/data:/backup/gitlab/data:ro
      - ./data/gitlab/logs:/backup/gitlab/logs:ro
      - ./data/gitlab/config:/backup/gitlab/config:ro

Do:
docker-compose up -d
docker exec backup backup
level=error msg="Fatal error running backup: takeBackup: error compressing backup folder: archive/tar: sockets not supported"

• What is the expected behavior?
  Ignore sockets and create tar file. Maybe a info for the user in the log.

• What is the motivation / use case for changing the behavior?
  Increases the compatibility

• Please tell us about your environment:

  • Image version: 2.10.0
  • Docker version: 20.10.12
  • docker-compose version: 2.2.3

[m90]

Thanks for raising this. This is an issue upstream at https://github.com/m90/targz, but luckily I am in control of that repo so we should be able to fix it.

I'm not entirely sure how to fix it yet though. It seems that good old command line tar seems to ignore sockets (thus creating an archive), but still exits non-zero in such cases https://serverfault.com/questions/525805/getting-errors-while-making-backup-of-whole-centos-with-tar unless you explicitly exclude the offending paths. I'd like to think about this a little longer so the fix for this doesn't turn into something with unforeseen consequences.

In the meantine, I think you should be able to work around this by actively excluding the offending sockets from the backup as described in #42 and here: https://stackoverflow.com/questions/29181032/add-a-volume-to-docker-but-exclude-a-sub-folder

[m90]

For reference, here's a similar issue and fix elsewhere GoogleContainerTools/kaniko#288

[m90]

I looked around more and it seems everyone who creates tar archives in native Go will just skip sockets, so I guess it's ok to do the same here.

A fix for this is now included in v2.10.1. Let me know if it works for you.

[rk0n]

Everything works like expected now. Thank you for fixing the issue that quick!