[Bug 1992485] Re: git cannot fetch: fatal: fetch-pack: unable to fork off sideband demultiplexer

[Lucas Kanashiro]

I tried to reproduce the bug based on this comment
(https://github.com/argoproj/argo-
cd/issues/9888#issuecomment-1271819234) in a regular x86 host but
everything worked as expected:

*21.04*:

```
root at 6d56a04fa8c1:~# git clone git at github.com:lucaskanashiro/pcs.git
Cloning into 'pcs'...
Enter passphrase for key '/root/.ssh/id_rsa': 
remote: Enumerating objects: 43789, done.
remote: Counting objects: 100% (1314/1314), done.
remote: Compressing objects: 100% (379/379), done.
remote: Total 43789 (delta 939), reused 1183 (delta 933), pack-reused 42475
Receiving objects: 100% (43789/43789), 20.58 MiB | 10.64 MiB/s, done.
Resolving deltas: 100% (35429/35429), done.
root at 6d56a04fa8c1:~# cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=21.04
DISTRIB_CODENAME=hirsute
DISTRIB_DESCRIPTION="Ubuntu 21.04"
root at 6d56a04fa8c1:~# git --version
git version 2.30.2
```

*22.04*:

```
root at 06bdbdc4c967:~# git clone git at github.com:lucaskanashiro/pcs.git
Cloning into 'pcs'...
Enter passphrase for key '/root/.ssh/id_rsa': 
remote: Enumerating objects: 43789, done.
remote: Counting objects: 100% (1314/1314), done.
remote: Compressing objects: 100% (379/379), done.
remote: Total 43789 (delta 939), reused 1183 (delta 933), pack-reused 42475
Receiving objects: 100% (43789/43789), 20.58 MiB | 10.42 MiB/s, done.
Resolving deltas: 100% (35429/35429), done.
root at 06bdbdc4c967:~# cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=22.04
DISTRIB_CODENAME=jammy
DISTRIB_DESCRIPTION="Ubuntu 22.04.1 LTS"
root at 06bdbdc4c967:~# git --version
git version 2.34.1
```

So this seems to be related to the VMware Tanzu infrastructure indeed.

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https://bugs.launchpad.net/bugs/1992485

Title:
  git cannot fetch: fatal: fetch-pack: unable to fork off sideband
  demultiplexer

Status in Ubuntu Docker Images:
  New
Status in Ubuntu:
  New
Status in git package in Ubuntu:
  Invalid

Bug description:
  There is a weird bug affecting the Ubuntu 22.04 Docker Image that
  seems to only be triggered in certain environments.

  For some reason, when running certain git commands, the following happens:
  https://github.com/argoproj/argo-cd/issues/9888

  ```
  fatal: fetch-pack: unable to fork off sideband demultiplexer
  ```

  On top of that, with the same 22.04 Docker Image, some errors related to GPG are happening:
  https://github.com/argoproj/argo-cd/issues/9809

  I believe this is due to an incompatible OS + Kernel combination, or
  due to some VMware customization.

  The entirety of the analysis is available in those two GitHub issues -
  although they're initially related to ArgoCD, the issue seems to be
  with the vanilla Ubuntu 22.04 Docker Image (and maybe with the Ubuntu
  4.15.0-167-generic kernel).

  Our enviornment:

  Kubernetes cluster running on VMware Tanzu (v1.21.9+vmware.1):
  Ubuntu 16.04.7 LTS 
  Linux 4.15.0-167-generic
  Container Runtime: Docker 20.10.9

  Image having issues:

  - ubuntu:22.10

  Steps to reproduce the issue:

  - Get a VMware Tanzu Kubernetes cluster
  - Start a Pod with ubuntu:21.10
  - Try to do `git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git` (or any repo, really)
  - Notice that you've successfully cloned the repo

  Now, with Ubuntu 22.10:

  - Get a VMware Tanzu Kubernetes cluster
  - Start a Pod with ubuntu:22.10
  - Try to do `git clone git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git` (or any repo, really)

  Result:
  Cloning into 'linux'...
  error: cannot create async thread: Operation not permitted
  fatal: fetch-pack: unable to fork off sideband demultiplexer

  
  We believe this might be an issue with the Ubuntu 22.10 Docker image (?) and VMware Tanzu together.

  We've noticed that libpthread is not linked in the git binary, and
  that might explain the fork issue, althoguh not completely.

  We've also noticed (but this should be OK?) that we don't have enough
  entropy on /dev/random (being a VM), but I don't think this is really
  the problem.

  Can someone help us out and point us in the right direction?
  We can eventually continue the conversation in one of the two above mentioned ArgoCD issues.

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