`usm cp`¶

Copy files across local paths, blobfuse2 mountpoints, and https:// Azure Blob URLs, delegating to azcopy whenever Azure Storage is on either side. Much faster than copying through the FUSE filesystem.

usm cp [--use-az] <source>... <destination>
usm cp --install

How it picks the transport¶

For each source/destination, usm cp checks whether the path is an Azure blob — either an https://<account>.blob.core.windows.net/... URL or a path under a known blobfuse2 mountpoint (it inspects the active blobfuse2 processes to figure that out). If at least one side is "Azure", it generates the equivalent azcopy URL and shells out to azcopy copy. Otherwise it falls back to a regular cp -r.

When a blob path is involved, usm cp makes sure azcopy is available, auto-installing it on first use if it is not found on PATH or in the usm-managed location (~/.cache/usm/bin/azcopy).

`https://` blob URLs¶

An https:// blob address is used as-is — the account/container are not re-derived to build the URL. By default a fresh SAS token is generated via az (parsing the account and container out of the URL only for that) and appended when the URL has none. URLs that already carry a sig= SAS token are left untouched. Pass --use-az to skip SAS generation entirely and let azcopy authenticate via your Azure CLI login instead.

# Local → https blob (SAS generated on the fly)
usm cp ./build https://acct.blob.core.windows.net/release/2025-06/

# https blob → local (URL already has a SAS token; used verbatim)
usm cp "https://acct.blob.core.windows.net/data/raw?sv=...&sig=..." ./inbox

Installing azcopy¶

# Download the latest azcopy for this OS/arch into ~/.cache/usm/bin
usm cp --install

Builds are mapped for Linux, macOS, and Windows (amd64/arm64). Set $USM_AZCOPY_BIN to point at an existing binary to bypass the managed copy.

Examples¶

# Local copy (just shells out to cp -r)
usm cp ./project ./project-backup

# Local → blob (uses azcopy)
usm cp ./build /mnt/data/release-2025-06/

# Blob → local
usm cp /mnt/data/raw ./inbox

# Blob → blob (across containers)
usm cp /mnt/data/foo /mnt/archive/foo

Flags¶

Flag	Effect
`--use-az`	Authenticate `azcopy` via Azure CLI login instead of generating SAS tokens.
`--dry-run` / `-d`	Print the azcopy/cp command without executing.
`--install`	Download and install the latest `azcopy` (linux/mac/windows), then exit.

Prerequisites¶

A blobfuse2 mount created via usm blobmount (or set up yourself with the same config layout), or an https:// blob URL.
azcopy — auto-installed on demand, or install it explicitly with usm cp --install (override with $USM_AZCOPY_BIN).
az CLI logged in (used to generate SAS tokens by default, or as the azcopy credential when --use-az is set).

Source¶

scripts/cp.py. Python script; uses psutil + pyyaml to read the mount metadata.

usm cp¶