Add support for --follow-link option in podman cp #16585

htjain · 2022-11-22T11:53:42Z

Is this a BUG REPORT or FEATURE REQUEST? (leave only one on its own line)

/kind feature

Description

Currently podman cp doesn't support for --follow-link like docker cp does.

Steps to reproduce the issue:

podman cp --follow-link xyz.tar container:/tmp/

Describe the results you received:
Error: unknown flag: --follow-link

Describe the results you expected:
File cp command should copy target file to container.

Additional information you deem important (e.g. issue happens only occasionally):

Output of podman version:

$ podman version
Version:      3.4.7
API Version:  3.4.7
Go Version:   go1.19.2
Built:        Thu Jan  1 05:30:00 1970
OS/Arch:      linux/arm64

Output of podman info:

$ podman info
host:
  arch: arm64
  buildahVersion: 1.23.1
  cgroupControllers:
  - cpu
  - pids
  cgroupManager: systemd
  cgroupVersion: v2
  conmon:
    package: 'conmon: /usr/bin/conmon'
    path: /usr/bin/conmon
    version: 'conmon version 2.1.3, commit: unknown'
  cpus: 4
  distribution:
    codename: bookworm
    distribution: debian
    version: unknown
  eventLogger: journald
  hostname: raspberrypi
  idMappings:
    gidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
    uidmap:
    - container_id: 0
      host_id: 1000
      size: 1
    - container_id: 1
      host_id: 100000
      size: 65536
  kernel: 5.15.76-v8+
  linkmode: dynamic
  logDriver: journald
  memFree: 201830400
  memTotal: 3529732096
  ociRuntime:
    name: runc
    package: 'runc: /usr/bin/runc'
    path: /usr/bin/runc
    version: |-
      runc version 1.1.4+ds1
      commit: 1.1.4+ds1-1
      spec: 1.0.2-dev
      go: go1.19
      libseccomp: 2.5.4
  os: linux
  remoteSocket:
    path: /run/user/1000/podman/podman.sock
  security:
    apparmorEnabled: false
    capabilities: CAP_CHOWN,CAP_DAC_OVERRIDE,CAP_FOWNER,CAP_FSETID,CAP_KILL,CAP_NET_BIND_SERVICE,CAP_SETFCAP,CAP_SETGID,CAP_SETPCAP,CAP_SETUID,CAP_SYS_CHROOT
    rootless: true
    seccompEnabled: true
    seccompProfilePath: /usr/share/containers/seccomp.json
    selinuxEnabled: false
  serviceIsRemote: false
  slirp4netns:
    executable: /usr/bin/slirp4netns
    package: 'slirp4netns: /usr/bin/slirp4netns'
    version: |-
      slirp4netns version 1.2.0
      commit: 656041d45cfca7a4176f6b7eed9e4fe6c11e8383
      libslirp: 4.7.0
      SLIRP_CONFIG_VERSION_MAX: 4
      libseccomp: 2.5.4
  swapFree: 26738688
  swapTotal: 104853504
  uptime: 69h 57m 46.53s (Approximately 2.88 days)
plugins:
  log:
  - k8s-file
  - none
  - journald
  network:
  - bridge
  - macvlan
  volume:
  - local
registries: {}
store:
  configFile: /home/pi/.config/containers/storage.conf
  containerStore:
    number: 0
    paused: 0
    running: 0
    stopped: 0
  graphDriverName: vfs
  graphOptions: {}
  graphRoot: /home/pi/.local/share/containers/storage
  graphStatus: {}
  imageStore:
    number: 19
  runRoot: /run/user/1000/containers
  volumePath: /home/pi/.local/share/containers/storage/volumes
version:
  APIVersion: 3.4.7
  Built: 0
  BuiltTime: Thu Jan  1 05:30:00 1970
  GitCommit: ""
  GoVersion: go1.19.2
  OsArch: linux/arm64
  Version: 3.4.7

Package info (e.g. output of rpm -q podman or apt list podman or brew info podman):

$ apt list podman
Listing... Done
podman/testing,now 3.4.7+ds1-3+b3 arm64 [installed]
podman/testing 3.4.7+ds1-3+b3 armhf

Have you tested with the latest version of Podman and have you checked the Podman Troubleshooting Guide? (https://github.com/containers/podman/blob/main/troubleshooting.md)

Yes

Additional environment details (AWS, VirtualBox, physical, etc.):
Same behavior on other OSs

The text was updated successfully, but these errors were encountered:

rhatdan · 2022-11-22T16:58:46Z

@htjain I started working on this a while back, but have too many other higher priorities now to finish in a reasonable amount of time.

If you were interested in taking it over, we could move it forward.

htjain · 2022-11-23T02:36:03Z

@rhatdan I can take it up. #15730 this PR you are talking about ?

rhatdan · 2022-11-23T10:07:12Z

Yes. It is all yours.

github-actions · 2022-12-24T00:05:48Z

A friendly reminder that this issue had no activity for 30 days.

rhatdan · 2023-01-03T18:58:13Z

@htjain any progress?

github-actions · 2023-02-03T00:07:33Z

A friendly reminder that this issue had no activity for 30 days.

rhatdan · 2023-02-03T23:16:39Z

@flouthoc PTAL

github-actions · 2023-03-06T00:07:44Z

A friendly reminder that this issue had no activity for 30 days.

danishprakash · 2023-03-10T14:50:52Z

@rhatdan I'd like to look into this.

flouthoc · 2023-03-10T15:02:03Z

@danishprakash Thanks assigned it to you :)

danishprakash · 2023-03-14T12:17:55Z

While triaging, I found some issues with what we're trying to achieve which I'd like to clear before I move on. It looks like

In docker cp, if you don't specify the --follow-link flag, docker would just copy the link and not the destination file. But if you do specify that flag, it would follow the link and copy the target to the destination.

$ docker run -d --rm -it --name test opensuse/tumbleweed bash

$ ls -al /tmp/file
/tmp/file -> /home/user/config/target

$ docker cp /tmp/file test:/tmp/file
$ docker exec test ls -al /tmp/file
/tmp/file -> /home/user/config/target 	# this doesn't exist of course

$ docker cp --follow-link /tmp/file test:/tmp/file
$ docker exec test ls -al /tmp/file
/tmp/file 								# with the contents for the symbolic link target

Now, podman, by default, follows the link without the --follow-link flag. So the question would be, do we change the current cp behavior to conform to docker's and add the --follow-link flag to do what it does right now. Or we leave it as is and document the behaviour? Or I might've missed something and the above is not right, in which case, I'd request either @rhatdan or @flouthoc to corroborate this once, thanks!

flouthoc · 2023-03-15T06:13:42Z

Okay podman indeed by default follows the symlink, i'd say we should default to how docker does and introduce a --follow-link, my only concern is that this is a breaking change and might break old users.

Again my vote is to default how docker does it but lets wait for others to take a look.

@rhatdan @containers/podman-maintainers WDYT ?

giuseppe · 2023-03-15T08:27:32Z

+1 to the Docker behavior. It is safer to not follow symlinks by default

vrothberg · 2023-03-15T08:34:42Z

Agreed. Docker compat is also a compelling reason to change the default.

danishprakash · 2023-03-15T08:57:16Z

That sounds great but as @flouthoc said, I'm also concerned that this is a breaking change and might break existing workflows. Either way, I'll start looking into the changes.

rhatdan · 2023-03-17T16:11:35Z

We need a boolean to change the default globally in containers.conf, then users who want the preivous default can customize their environment.

danishprakash · 2023-04-03T06:25:15Z

Tried a sample implementation here which included changes to both buildah and podman. The idea is to maintain the symlink even if the target isn't present on the container which would inevitably lead to an error when accessed. This is docker's behaviour too.

While passing --follow-link flag, podman would continue to do what it currently does.

We need a boolean to change the default globally in containers.conf, then users who want the preivous default can customize their environment.

I can go ahead and finalize the PRs in both the repos if the approach above sounds reasonable. Thoughts?

giuseppe · 2023-04-03T07:00:34Z

yes please open the PRs so we can comment on them

openshift-ci bot added the kind/feature Categorizes issue or PR as related to a new feature. label Nov 22, 2022

rhatdan mentioned this issue Nov 22, 2022

[WIP] Add support for podman cp --follow-link #15730

Closed

rhatdan assigned htjain Nov 23, 2022

github-actions bot added the stale-issue label Dec 24, 2022

rhatdan removed the stale-issue label Jan 3, 2023

github-actions bot added the stale-issue label Feb 3, 2023

rhatdan unassigned htjain Feb 3, 2023

github-actions bot removed the stale-issue label Feb 4, 2023

github-actions bot added the stale-issue label Mar 6, 2023

rhatdan removed the stale-issue label Mar 8, 2023

flouthoc assigned danishprakash Mar 10, 2023

danishprakash mentioned this issue Mar 29, 2023

docker differences as of November 2022 #16543

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This was referenced Apr 3, 2023

[wip] cp.go: docker compat w/ --follow-link option #18020

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copier: retain symlink target w/ follow-link containers/buildah#4703

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Add support for --follow-link option in podman cp #16585

Add support for --follow-link option in podman cp #16585

htjain commented Nov 22, 2022

rhatdan commented Nov 22, 2022

htjain commented Nov 23, 2022

rhatdan commented Nov 23, 2022

github-actions bot commented Dec 24, 2022

rhatdan commented Jan 3, 2023

github-actions bot commented Feb 3, 2023

rhatdan commented Feb 3, 2023

github-actions bot commented Mar 6, 2023

danishprakash commented Mar 10, 2023

flouthoc commented Mar 10, 2023

danishprakash commented Mar 14, 2023

flouthoc commented Mar 15, 2023

giuseppe commented Mar 15, 2023

vrothberg commented Mar 15, 2023

danishprakash commented Mar 15, 2023

rhatdan commented Mar 17, 2023

danishprakash commented Apr 3, 2023

giuseppe commented Apr 3, 2023

Add support for --follow-link option in podman cp #16585

Add support for --follow-link option in podman cp #16585

Comments

htjain commented Nov 22, 2022

rhatdan commented Nov 22, 2022

htjain commented Nov 23, 2022

rhatdan commented Nov 23, 2022

github-actions bot commented Dec 24, 2022

rhatdan commented Jan 3, 2023

github-actions bot commented Feb 3, 2023

rhatdan commented Feb 3, 2023

github-actions bot commented Mar 6, 2023

danishprakash commented Mar 10, 2023

flouthoc commented Mar 10, 2023

danishprakash commented Mar 14, 2023

flouthoc commented Mar 15, 2023

giuseppe commented Mar 15, 2023

vrothberg commented Mar 15, 2023

danishprakash commented Mar 15, 2023

rhatdan commented Mar 17, 2023

danishprakash commented Apr 3, 2023

giuseppe commented Apr 3, 2023