NEM_HOME

All of nem’s on-disk state lives under one per-user directory: $NEM_HOME, default ~/.nem. Set NEM_HOME to relocate it — nem writes nothing outside it except the managed shell-rc block that nem activate installs, and nothing anywhere needs root.

Layout

~/.nem/
├── config.yaml              # nem's configuration: catalog list, host settings
├── nem.toml                 # global manifest
├── nem.lock                 # global lockfile
├── lock                     # internal process lock — never deleted
├── usage.json               # last-resolution stamps; read by `clean --unused`
├── tmp/                     # download staging
├── packages/
│   └── <name>/<version>/    # one immutable tree per installed version
└── catalogs/
    └── <name>/store/        # local mirror of an oci catalog

• config.yaml — see config.yaml.
• nem.toml / nem.lock — the global twins of the project files; see nem.toml and nem.lock.
• lock — a flock guarding writes to manifests, locks, config, and catalog syncs. The file itself is never deleted.
• usage.json — last-resolution stamps for installed versions; consulted by clean --unused to decide what’s eligible for eviction.
• tmp/ — in-flight downloads, cleaned opportunistically.
• packages/<name>/<version>/ — one installed version, addressed by name and exact version.
• catalogs/<name>/store/ — the local mirror of an oci catalog’s index; dir catalogs have nothing here, since they’re read straight from their configured path.

Install properties

A version counts as installed exactly when its directory exists under packages/. Installs commit by atomic rename, so a half-finished install is never visible as an installed version — either the whole tree is there, or nothing is. Interrupted staging left behind by an install that didn’t finish is swept up by later runs.

Reclaiming space

nem clean

Bare nem clean touches only provable garbage — leaked build staging, leaked downloads, partial installs — and never prompts, so it’s safe to run unattended.

• --unused <days|hours> and --all go further and evict installed package versions; nem sync reinstalls whatever a project still needs. Either one asks for confirmation before deleting unless -y/--yes is given.
• --dry-run prints the plan without deleting anything.
• --grace (default 1h) leaves recently-touched reclaimable paths alone.
• -y, --yes skips the confirmation prompt for --unused/--all.

See Managing environments for the full command reference, including the caveat on how --unused measures “unused.”