# How do I update an environment in Julia?

**URL:** <https://discourse.julialang.org/t/how-do-i-update-an-environment-in-julia/93826>\
**Category:** General Usage\
**Tags:** package, package-manager, environment\
**Created:** [January 31, 2023, 5:08pm UTC](https://discourse.julialang.org/t/how-do-i-update-an-environment-in-julia/93826 "2023-01-31T17:08:38Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![ffevotte](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/ffevotte/32/6587_2.png) [@ffevotte](https://discourse.julialang.org/u/ffevotte)\
**Post date:** [January 31, 2023, 5:28pm UTC](https://discourse.julialang.org/t/how-do-i-update-an-environment-in-julia/93826/2 "2023-01-31T17:28:16Z")

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> [@danielsoutar](#):
>
> My understanding (obviously correct me if I’m wrong) is that you would do this in `Pkg`. You might `instantiate` in the current environment.

Yes, this is correct. `Pkg` should be used to manipulate environments, and `instantiate` is the command you want to create (“instantiate”) an environment that is consistent with the current contents of `Project.toml`. The description of the complete environment is saved in the `Manifest.toml`.

EDIT: To go a bit more into the details: `Pkg.resolve` is used to build a consistent environment and save it into `Manifest.toml`, and then `Pkg.instantiate` is responsible for taking the environment described in `Manifest.toml` and making sure all listed packages and versions are installed on your machine.

If no Manifest exists, calling `instantiate` will implicitly call `resolve` first. If a Manifest already exists but is not consistent with the current description of the project, you’ll need to re-`resolve` and `instantiate` will tell you so.

> [@danielsoutar](#):
>
> Alternatively a ‘clean build’ would mean deleting the Manifest and regenerating it via `activate .; instantiate` in `Pkg`.

Do you mean “clean” in that this simulates what would happen to a new user of the package? Then that is true.

If my understanding of `Pkg` is correct, this should be equivalent to running `update` instead of `resolve`. IIUC, the difference between these two commands is that `resolve` tries to determine a minimal set of changes (w.r.t. the current environment described in `Manifest.toml` if it exists) that are needed to make the environment consistent with the requirements described in `Project.toml`. On the other hand, `update` tries to find an environment that is as up-to-date as possible (i.e. it will install newer versions of dependencies when available, even if it is not strictly necessary to conform to the project requirements).

> [@danielsoutar](#):
>
> The latter could be important for ensuring that the update to `SomePackage` propagates to all other packages.

Not sure what you mean by that. Running `resolve` will ensure that any update you make in the compatibility bounds of your project will be reflected in the environment. Running `update` will additionally try to bring into the project any newer version of your dependencies that might have been released since the last time you instantiated/updated your environment.

> [@danielsoutar](#):
>
> My colleague says that in order to have a clean build, you need to remove the entire `.julia` directory in the home directory. This seems extreme to me, but maybe this is occasionally necessary.

Please do not delete the entire `.julia` directory. It is usually not needed and may have unintended consequences (including the loss of some data that can’t be recovered from the Internet).

See for example this recent discussion about deleting the `.julia` directory:

> [@Danger of deleting .julia?](https://discourse.julialang.org/t/danger-of-deleting-julia/93372):
>
> [From thread](https://discourse.julialang.org/t/julia-1-9-0-beta2-precompilation-taking-almost-twice-as-long/92498/20) Please refrain from doing such dangerous suggestions again. What is the danger of deleting .julia?

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