"IOError: [Errno 71] Protocol error" when reading a file with python in a virtualbox debian machine

Question

I try to open and read a file in Python 2.7.3 which is running in a virtual machine:

Host: Ubuntu 14.04 LTS

Guest: Debian Wheezy 7.5

VM-Software: VirtualBox V4.3.30

In the Python console inside the VM, I enter the following:

>>> f = open("Testing/results.txt", "w+")
>>> f.read()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IOError: [Errno 71] Protocol error

The file exists and is located in a shared folder. If I try to do the same on a file which is located on the file system of the VM, it works fine. Also opening the file with mode "r+" or "a+", it works but it doesn't get truncated. Truncating the file manually after opening in read mode is working and currently, I use that as a workaround. But maybe anybody here knows, why this error occurs?

My guess is that it's a permissions problem on the shared folder from the Host side. Can you try making the shared folder more permissive from the Host? — Joe Young, Aug 01 '15 at 01:23
What type of share are you using? Windows? SAMBA? VirtualBox Share? — Justin Andrusk, Jul 10 '17 at 14:53
https://docs.python.org/3.6/tutorial/inputoutput.html#reading-and-writing-files f = open("Testing/results.txt", "rb+") should work for you. — AjayShelar, Jan 21 '20 at 11:35
Where is the python script in relation to the file you are trying to open? Is it in the same directory? — Lateralus, May 09 '20 at 01:54
2. Most results online seem to indicate it is error 71 of the Linux system — xjcl, Jun 04 '20 at 17:11

score 1 · Answer 1 · answered Aug 25 '20 at 21:43

The most probable cause of this error is a bug in the VirtualBox Linux Guest Additions, more specifically, one of its device drivers vboxguest (which communicates with the host) and vboxsf (which provides shared folder services on the guest on top of vboxguest).

Background: When using the Linux read(2) system call on VirtualBox shared files, specific conditions make the VirtualBox driver(s) fail with error 71 (EPROTO) – Protocol error (see tickets below). The error originates in the Linux kernel space and propagates via the C library to applications (see errno(3)). In this case, the application happens to be the Python interpreter.

There is nothing wrong with the Python code or file permissions. The code just performs a legitimate sequence of operations which triggers the error.

Relevant VirtualBox tickets:

According to ticket #8463, this bug (or a related one) was fixed in VirtualBox Linux Guest Additions 5.1.14 / 5.0.32 on January 17, 2017.

"IOError: [Errno 71] Protocol error" when reading a file with python in a virtualbox debian machine

1 Answers1