Mamba should be installed to the base environment#

Installing Mamba to an environment other than base is not supported. Mamba must be installed in the base environment alongside Conda, and no other packages may be installed into base.

No other packages should be installed to base#

Installing packages other than Conda and Mamba into the base environment is not supported. Mamba must live in the same environment as Conda, and Conda does not support having packages other than Conda itself and its dependencies in base.

Mixing the defaults and conda-forge channels#

Using the defaults and conda-forge channels at the same time is not supported, eg. using a channel configuration like this:

# NOT supported!
  - conda-forge
  - defaults

The Anaconda default channels are incompatible with conda-forge.

Mamba broken after Conda update#

Mamba sometimes stops working if you update to a very recent version of Conda. Please downgrade to the latest working a version and file a bug report in the Mamba bug tracker if the problem has not been reported yet.

Windows long paths#

Windows API historically supports paths up to 260 characters. While it’s now possible to used longer ones, there are still limitations related to that.

libmamba internally relies on \\?\ prefixing to handle such paths. If you get error messages advertising such prefix, please have look at the following steps:

Long paths support has to be activated#

source: Robocorp troubleshooting documentation

  1. Open the Local Group Policy Editor application: - Start –> type gpedit.msc –> Enter:

  2. Navigate to Computer Configuration > Administrative Templates > System > Filesystem. On the right, find the “Enable win32 long paths” item and double-click it

  3. Change the setting to Enabled

  4. Exit the Local Group Policy Editor and restart your computer (or sign out and back in) to allow the changes to finish

If the problem persists after those steps, try the following:

  1. Open the Registry Editor application: - Start –> type regedit.msc and press Enter:

  2. Navigate to HKEY-LOCAL-MACHINE > SYSTEM > CurrentControlSet > Control > FileSystem. On the right, find the LongPathsEnabled item and double-click it

  3. Change the Value data: to 1

  4. Exit the Registry Editor

cmd.exe does not support calls to long prefixes#

While cmd.exe shell support long paths prefixing for directory operations such as dir, it doesn’t allow to call an executable or a batch file located at a long path prefix.

Thus, the following cases will fail:

  • completely

    • calling executables located at long prefixes

    • installation of packages with pre/post linking or activation .bat scripts

  • partially

    • pre-compilation of noarch packages, with no impact on capability to use the package but removing it will let artifacts (pycache) on the filesystem

Hangs during install in QEMU#

When using Mamba/Micromamba inside a QEMU guest, installing packages may sometimes hang forever due to an issue with QEMU and glibc. As a workaround, set G_SLICE=always-malloc in the QEMU guest, eg.:

export G_SLICE=always-malloc
mamba install ...

See #1611 for discussion.