Conda installation for mrtrix3

1

Hello all !

I have a question regarding the conda installation for mrtrix3.

Since 2024 Anaconda updated their Terms of Service and access to community-hosted channels on anaconda.org is now restricted for users connecting from institutional IP addresses (universities, hospitals, research centers) unless a paid license or access token is provided.

In practice, this means that conda install -c mrtrix3 mrtrix3 fails with an HTTP 403 Forbidden error when run from such networks. This restriction does not affect the conda-forge channel as it is served through its own independent infrastructure and remains freely accessible regardless of the user’s IP.

Would you be open to publishing the package on the conda-forge channel ?

Thank you very much for your work ! (Apologize if this message does not have the right tag)

Alice

2

Hi Alice,

Did you try Miniforge ?
Install conda:

cd ~
wget https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge3-Linux-x86_64.sh
bash Miniforge3-Linux-x86_64.sh

or

cd ~
curl -L -O https://github.com/conda-forge/miniforge/releases/latest/download/Miniforge3-Linux-x86_64.sh
bash Miniforge3-Linux-x86_64.sh

source ~/.bashrc

#check install
conda --version
mamba --version

#optional:
conda config --set auto_activate_base false
conda config --set channel_priority strict

Install MRtrix3 can be created with:

mamba create -n mrtrix3 -c conda-forge -c MRtrix3 mrtrix3 libstdcxx-ng
3

Hello William,

Thanks for the reply. Yes, I use miniconda, and have no issue with other packages hosted on conda-forge. The problem is when packages are accessible via a channel hosted on anaconda, which seems to be the case for mrtrix3.

To show an example of the issue, I tried fetching the json index file for channel mrtrix3. This file is required when installing a package, whether the manager is conda or mamba.

  • On my machine bound by an institutional account :
>>> $ curl -I https://conda.anaconda.org/mrtrix3/linux-64/repodata.json

HTTP/2 403

**content-type**: text/html; charset=UTF-8

**cache-control**: no-cache
  • On my personal one :
>>> $ curl -I https://conda.anaconda.org/mrtrix3/linux-64/repodata.json

HTTP/2 200

**date**: Wed, 24 Jun 2026 08:36:10 GMT

**content-type**: application/json

**content-length**: 5697

**cf-ray**: a10a673bcfaed706-CDG

**cf-cache-status**: DYNAMIC

**cache-control**: max-age=60, public

**last-modified**: Tue, 21 Oct 2025 21:47:12 GMT

**server**: cloudflare

**x-download-options**: noopen

**strict-transport-security**: max-age=15552000

**vary**: Cookie

**content-security-policy**: frame-ancestors 'self';

**referrer-policy**: same-origin

**x-content-type-options**: nosniff

**set-cookie**: x_csrf_token=Ijk2NWE5OTA0M2Q5NTZhZTdiNjZlZmMzZTBjYzZmZmU3MDY4NmQyODgi.ajuW-g.kZNnfNZk7_Nk4nrZmFJEJEUxGyk; Path=/

**set-cookie**: session=eyJjc3JmX3Rva2VuIjoiOTY1YTk5MDQzZDk1NmFlN2I2NmVmYzNlMGNjNmZmZTcwNjg2ZDI4OCJ9.ajuW-g.6GlCD9oONW1E3W_ZaMWa1CgH0qg; Domain=anaconda.org; Secure; HttpOnly; Path=/

**set-cookie**: prex-ui-wheels=; Path=/; Max-Age=0; Secure; SameSite=Lax

**set-cookie**: \__cf_bm=kUx5t7e_B_XEzisStxjj2URFqDZugp5wNS9g7kma2II-1782290170.2014444-1.0.1.1-Fek6kcRYJOpAgLZRSpGSRqIV1qrImwfn.HWe7m0TFeGU4w0RlEVoWjjYd4A9dtlyk8MzgeDXiwdw7Y1YV_TwFvU5CPmspQXg7yFS9WamntD8gPxgJnAbSxm86j4YGeZIbZN7TiCH1EIxsHQytA2wIw; HttpOnly; SameSite=None; Secure; Path=/; Domain=anaconda.org; Expires=Wed, 24 Jun 2026 09:06:10 GMT
4

Hi Alice,

I guess you already did, but did you ask your system administrator to open up/prioritize/mirror conda-forge for mrtrix?

Can you build a singularity/apptainer container?

5

Hello William,

In my application for now I cannot use a container but that might change. I doubt my administrator would let me do that but I thought mrtrix3 was not on conda-forge. Could you explain to me why that would work ?

Thank you very much !

Best,

6

Hi Alice

I am not an expert. I was the first thing to try after a search. There are probably lots of other stuff one could try. However, I would first talk to your system manager

BW

William