Frequently Asked Questions
Why does my node_modules folder use disk space if packages are stored in a global store?#
pnpm creates hard links from the global store to the project's node_modules
folders. Hard links point to the same place on the disk where the original
files are. So, for example, if you have foo in your project as a dependency
and it occupies 1MB of space, then it will look like it occupies 1MB of space in
the project's node_modules folder and the same amount of space in the global
store. However, that 1MB is the same space on the disk addressed from two
different locations. So in total foo occupies 1MB, not 2MB.
For more on this subject:
- Why do hard links seem to take the same space as the originals?
- A thread from the pnpm chat room
- An issue in the pnpm repo
Does it work on Windows?#
Short answer: Yes. Long answer: Using symbolic linking on Windows is problematic to say the least, however, pnpm has a workaround. For Windows, we use junctions instead.
But the nested node_modules approach is incompatible with Windows?#
Early versions of npm had issues because of nesting all node_modules (see
this issue. However, pnpm does not create deep folders, it stores all packages
flatly and uses symbolic links to create the dependency tree structure.
What about circular symlinks?#
Although pnpm uses linking to put dependencies into node_modules folders,
circular symlinks are avoided because parent packages are placed into the same
node_modules folder in which their dependencies are. So foo's dependencies
are not in foo/node_modules, but foo is in node_modules together with its
own dependencies.
Why have hard links at all? Why not symlink directly to the global store?#
One package can have different sets of dependencies on one machine.
In project A foo@1.0.0 can have a dependency resolved to bar@1.0.0, but
in project B the same dependency of foo might resolve to bar@1.1.0; so,
pnpm hard links foo@1.0.0 to every project where it is used, in order to
create different sets of dependencies for it.
Direct symlinking to the global store would work with Node's
--preserve-symlinks flag, however, that approach comes with a plethora of its
own issues, so we decided to stick with hard links. For more details about why
this decision was made, see this issue.
Does pnpm work across multiple drives or filesystems?#
The package store should be on the same drive and filesystem as installations, otherwise packages will be copied, not linked. This is due to a limitation in how hard linking works, in that a file on one filesystem cannot address a location in another. See Issue #712 for more details.
pnpm functions differently in the 2 cases below:
Store path is specified#
If the store path is specified via the store config, then copying occurs between the store and any projects that are on a different disk.
If you run pnpm install on disk A, then the pnpm store must be on disk A.
If the pnpm store is located on disk B, then all required packages will be
directly copied to the project location instead of being linked. This severely
inhibits the storage and performance benefits of pnpm.
Store path is NOT specified#
If the store path is not set, then multiple stores are created (one per drive or filesystem).
If installation is run on disk A, the store will be created on A
.pnpm-store under the filesystem root. If later the installation is run on
disk B, an independent store will be created on B at .pnpm-store. The
projects would still maintain the benefits of pnpm, but each drive may have
redundant packages.
What does pnpm store prune do? Is it harmful?#
The command pnpm store prune removes unreferenced packages.
Unreferenced packages are packages that are not used by any projects on the system. Packages can become unreferenced after most installation operations, for instance when dependencies are made redundant.
For example, during pnpm install, package foo@1.0.0 is updated to
foo@1.0.1. pnpm will keep foo@1.0.0 in the store, as it does not
automatically remove packages. If package foo@1.0.0 is not used by any other
project on the system, it becomes unreferenced. Running pnpm store prune would
remove foo@1.0.0 from the store.
Running pnpm store prune is not harmful and has no side effects on your
projects. If future installations require removed packages, pnpm will download
them again.
It is best practice to run pnpm store prune occasionally to clean up the
store, but not too frequently. Sometimes, unreferenced packages become required
again. This could occur when switching branches and installing older
dependencies, in which case pnpm would need to re-download all removed packages,
briefly slowing down the installation process.
What does pnpm stand for?#
pnpm stands for performant npm.
@rstacruz came up with the name.
pnpm does not work with <YOUR-PROJECT-HERE>?#
In most cases it means that one of the dependencies require packages not
declared in package.json. It is a common mistake caused by flat
node_modules. If this happens, this is an error in the dependency and the
dependency should be fixed. That might take time though, so pnpm supports
workarounds to make the buggy packages work.
Solution 1#
In the following example, a dependency does not have the iterall module in
its own list of deps.
The easiest solution to resolve missing dependencies of the buggy packages is to
add iterall as a dependency to our project's package.json.
You can do so, by installing it via pnpm add iterall, and will be
automatically added to your project's package.json.
"dependencies": { ... "iterall": "^1.2.2", ... }Solution 2#
One of the solutions is to use hooks for adding the missing
dependencies to the package's package.json.
An example was Webpack Dashboard which wasn't working with pnpm. It has
since been resolved such that it works with pnpm now.
It used to throw an error:
Error: Cannot find module 'babel-traverse' at /node_modules/inspectpack@2.2.3/node_modules/inspectpack/lib/actions/parseThe problem was that babel-traverse was used in inspectpack which
was used by webpack-dashboard, but babel-traverse wasn't specified in
inspectpack's package.json. It still worked with npm and yarn because
they create flat node_modules.
The solution was to create a .pnpmfile.cjs with the following contents:
module.exports = { hooks: { readPackage: (pkg) => { if (pkg.name === "inspectpack") { pkg.dependencies['babel-traverse'] = '^6.26.0'; } return pkg; } }};After creating a .pnpmfile.cjs, delete pnpm-lock.yaml only - there is no need
to delete node_modules, as pnpm hooks only affect module resolution. Then,
rebuild the dependencies & it should be working.
Solution 3#
In case there are too many issues, you can use the shamefully-hoist option.
This creates a flat node_modules structure similar to the one created by npm
or yarn, which is not recommended as avoiding this structure is the primary
purpose of pnpm's node_modules approach.
To use it, try pnpm install --shamefully-hoist.