How to Change the Default Installation Directory for MongoDB Versions in m

Set the M_PREFIX environment variable to your desired parent directory before running m to relocate MongoDB binaries from the default $HOME/.local/m to any custom location.

The m tool by aheckmann simplifies MongoDB version management, but by default it installs all binaries under your home directory. If you need to change the default installation directory to a different partition, shared network location, or system-wide path, you can override the behavior using environment variables defined in the source code.

Understanding the Default Path Structure

According to bin/m (lines 9-15), m determines its root storage location using the M_PREFIX environment variable. When unset, m falls back to $HOME/.local and creates a subdirectory named m to house all files.

Under this prefix, the tool organizes downloaded artifacts as follows:

• <M_PREFIX>/m/versions/ – MongoDB server binaries (mongod, mongos)
• <M_PREFIX>/m/tools/ – Database Tools (mongodump, mongorestore, mongoimport)
• <M_PREFIX>/m/shell/ – MongoDB Shell (mongosh)

The symbolic links to active binaries are placed in <M_PREFIX>/bin by default, though this destination is separately configurable.

Change the Installation Directory with M_PREFIX

To change where MongoDB versions are installed, export M_PREFIX with the path to your preferred parent directory before invoking any m commands. The tool automatically appends /m and creates the required subdirectories.

Temporary Change (Per Command)

For a one-off installation to a custom location, prefix the command:

M_PREFIX=/opt/mongodb m stable

This installs the latest stable MongoDB version under /opt/mongodb/m/versions/ instead of the default home directory.

Persistent Change (Shell Configuration)

To permanently change the installation directory, add the export to your shell startup file:

# ~/.bashrc, ~/.zshrc, or ~/.bash_profile

export M_PREFIX=/opt/mongodb
export M_BIN_DIR=/opt/mongodb/bin  # optional: customize symlink location

After reloading your shell (source ~/.bashrc), all subsequent m commands will use the new paths.

Customize the Binary Symlink Location (M_BIN_DIR)

As implemented in bin/m (lines 14-16), the directory where m creates symbolic links to the active MongoDB binaries is controlled by the M_BIN_DIR environment variable. This defaults to $M_PREFIX/bin but can be overridden independently if you need executables accessible from a specific location in your $PATH.

export M_PREFIX=/data/mongodb
export M_BIN_DIR=/usr/local/bin

With this configuration, m stores large binary files under /data/mongodb/m/ while placing lightweight symlinks in /usr/local/bin.

Verify Active Directories

After configuring these variables, confirm the active paths using built-in m commands:

m ls          # Lists installed versions from $M_PREFIX/m/versions

m bin 6.0.2   # Prints the full path to the mongod binary for version 6.0.2

Relocate an Existing Installation

If you have already installed MongoDB versions under the default $HOME/.local/m and want to move them to a new location:

1. Copy the existing directory structure to the new parent directory.
2. Update the M_PREFIX environment variable.
3. Rebuild the symbolic links to point to the new location.

# 1. Copy existing installations (preserve permissions)

cp -a $HOME/.local/m /opt/mongodb/m

# 2. Update environment variable

export M_PREFIX=/opt/mongodb

# 3. Recreate symlinks in the new bin directory

m reinstall 6.0.2

The m reinstall command forces m to recreate the symlink in the new M_BIN_DIR without re-downloading the binaries.

Summary

• Default behavior: m stores binaries under $HOME/.local/m, using M_PREFIX which defaults to $HOME/.local as defined in bin/m.
• Primary control: Set the M_PREFIX environment variable to change the parent directory of the m folder.
• Symlink control: Use M_BIN_DIR to customize where executable links are placed; it defaults to $M_PREFIX/bin.
• Migration path: Copy the existing m directory to the new location, update M_PREFIX, and run m reinstall for each version to refresh symlinks.

Frequently Asked Questions

How do I check the current installation directory used by m?

Run the command m bin <version> (e.g., m bin 6.0.2) to print the full path to the mongod binary. This output follows the pattern $M_PREFIX/m/versions/<version>/bin/mongod, revealing the active prefix location.

Can I use different installation directories for different terminal sessions?

Yes. Because m reads the M_PREFIX environment variable at runtime, you can set different values in different terminal sessions or shell scripts. Each session operates independently, allowing isolated MongoDB installations for different projects.

What happens if I change M_PREFIX after installing versions?

If you change M_PREFIX without moving the files, m will not find your previously installed versions and will treat the new location as empty. To migrate, copy the $HOME/.local/m directory to the new $M_PREFIX/m location and run m reinstall <version> to recreate the symlinks.

Is M_BIN_DIR required to be inside M_PREFIX?

No. While M_BIN_DIR defaults to $M_PREFIX/bin, you can set it to any directory such as /usr/local/bin or $HOME/bin. This is useful when storing large binaries on a separate partition (via M_PREFIX) while keeping executable links in a standard location already in your $PATH.

{
  "mcpServers": {
    "instagit": {
      "command": "npx",
      "args": ["-y", "instagit@latest"]
    }
  }
}