[yocto] Strange filesystem problem using docker on a pyro based system

[Peter Spierenburg]

I am building docker on a pyro based system. I'm using the overlay storage driver, and I am getting a strange result:


When I add a file to a container, any files in the same directory that come from the base image disappear... Here is a short script that highlights what I mean:


docker build -t test - <<"EOF" FROM debian RUN ls -laF /usr RUN ls -laF ./usr/bin RUN touch /usr/bin/bogus RUN ls -laF /usr RUN ls -laF ./usr/bin EOF docker run -it --name=test_container test sh -c "ls -laF /usr ; ls -laF ./usr/bin ; whoami && echo PASS || echo FAIL" docker logs test_container docker rm test_container docker rmi test


When I run the script above, creating the /usr/bin/bogus file causes all other files in /usr/bin to disappear, so that when the script tries to run the whoami command it fails with


sh: 1: whoami: not found


I figure that I have missed some important kernel config option. According to /usr/share/docker/contrib/check-config.sh:


info: reading kernel config from /proc/config.gz ...

Generally Necessary:
- cgroup hierarchy: properly mounted [/sys/fs/cgroup]
- CONFIG_NAMESPACES: enabled
- CONFIG_NET_NS: enabled
- CONFIG_PID_NS: enabled
- CONFIG_IPC_NS: enabled
- CONFIG_UTS_NS: enabled
- CONFIG_CGROUPS: enabled
- CONFIG_CGROUP_CPUACCT: enabled
- CONFIG_CGROUP_DEVICE: enabled
- CONFIG_CGROUP_FREEZER: enabled
- CONFIG_CGROUP_SCHED: enabled
- CONFIG_CPUSETS: enabled
- CONFIG_MEMCG: enabled
- CONFIG_KEYS: enabled
- CONFIG_VETH: enabled
- CONFIG_BRIDGE: enabled (as module)
- CONFIG_BRIDGE_NETFILTER: enabled (as module)
- CONFIG_NF_NAT_IPV4: enabled (as module)
- CONFIG_IP_NF_FILTER: enabled (as module)
- CONFIG_IP_NF_TARGET_MASQUERADE: enabled (as module)
- CONFIG_NETFILTER_XT_MATCH_ADDRTYPE: enabled (as module)
- CONFIG_NETFILTER_XT_MATCH_CONNTRACK: enabled (as module)
- CONFIG_NETFILTER_XT_MATCH_IPVS: enabled (as module)
- CONFIG_IP_NF_NAT: enabled (as module)
- CONFIG_NF_NAT: enabled (as module)
- CONFIG_NF_NAT_NEEDED: enabled
- CONFIG_POSIX_MQUEUE: enabled
- CONFIG_DEVPTS_MULTIPLE_INSTANCES: enabled

Optional Features:
- CONFIG_USER_NS: enabled
- CONFIG_SECCOMP: enabled
- CONFIG_CGROUP_PIDS: missing
- CONFIG_MEMCG_SWAP: missing
- CONFIG_MEMCG_SWAP_ENABLED: missing
- CONFIG_MEMCG_KMEM: enabled
- CONFIG_BLK_CGROUP: missing
- CONFIG_BLK_DEV_THROTTLING: missing
- CONFIG_IOSCHED_CFQ: enabled (as module)
- CONFIG_CFQ_GROUP_IOSCHED: missing
- CONFIG_CGROUP_PERF: enabled
- CONFIG_CGROUP_HUGETLB: missing
- CONFIG_NET_CLS_CGROUP: enabled (as module)
- CONFIG_CGROUP_NET_PRIO: enabled
- CONFIG_CFS_BANDWIDTH: enabled
- CONFIG_FAIR_GROUP_SCHED: enabled
- CONFIG_RT_GROUP_SCHED: enabled
- CONFIG_IP_VS: enabled (as module)
- CONFIG_IP_VS_NFCT: enabled
- CONFIG_IP_VS_RR: enabled (as module)
- CONFIG_EXT3_FS: missing
- CONFIG_EXT3_FS_XATTR: missing
- CONFIG_EXT3_FS_POSIX_ACL: missing
- CONFIG_EXT3_FS_SECURITY: missing
    (enable these ext3 configs if you are using ext3 as backing filesystem)
- CONFIG_EXT4_FS: enabled
- CONFIG_EXT4_FS_POSIX_ACL: enabled
- CONFIG_EXT4_FS_SECURITY: enabled
- Network Drivers:
  - "overlay":
    - CONFIG_VXLAN: missing
      Optional (for encrypted networks):
      - CONFIG_CRYPTO: enabled
      - CONFIG_CRYPTO_AEAD: missing
      - CONFIG_CRYPTO_GCM: missing
      - CONFIG_CRYPTO_SEQIV: missing
      - CONFIG_CRYPTO_GHASH: missing
      - CONFIG_XFRM: enabled
      - CONFIG_XFRM_USER: enabled (as module)
      - CONFIG_XFRM_ALGO: enabled (as module)
      - CONFIG_INET_ESP: missing
      - CONFIG_INET_XFRM_MODE_TRANSPORT: enabled
  - "ipvlan":
    - CONFIG_IPVLAN: missing
  - "macvlan":
    - CONFIG_MACVLAN: enabled
    - CONFIG_DUMMY: missing
  - "ftp,tftp client in container":
    - CONFIG_NF_NAT_FTP: enabled (as module)
    - CONFIG_NF_CONNTRACK_FTP: enabled (as module)
    - CONFIG_NF_NAT_TFTP: enabled (as module)
    - CONFIG_NF_CONNTRACK_TFTP: enabled (as module)
- Storage Drivers:
  - "aufs":
    - CONFIG_AUFS_FS: missing
  - "btrfs":
    - CONFIG_BTRFS_FS: missing
    - CONFIG_BTRFS_FS_POSIX_ACL: missing
  - "devicemapper":
    - CONFIG_BLK_DEV_DM: missing
    - CONFIG_DM_THIN_PROVISIONING: missing
  - "overlay":
    - CONFIG_OVERLAY_FS: enabled (as module)
  - "zfs":
    - /dev/zfs: missing
    - zfs command: missing
    - zpool command: missing

Limits:
- /proc/sys/kernel/keys/root_maxkeys: 1000000


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