user-app-development

name	user-app-development
description	Guide for developing, building, and running Nanvix user-space applications across supported runtimes and languages. Use this when asked about guest app implementation or execution.

User Application Development

Use this skill when the user asks about developing, building, or running user-space applications on Nanvix. User applications are programs that run inside the Nanvix guest environment.

Supported Languages and Examples

Application	Path	Lang	Runtime
hello-rust-nostd	src/user/hello-rust-nostd/	Rust	Bare-metal

Running Applications

Interactive Mode (recommended for development)

# Run a native application with console output.
./bin/nanvixd.elf \
    -console-file /dev/stdout \
    -- ./bin/hello-rust-nostd.elf

# Pass arguments to the application.
./bin/nanvixd.elf \
    -console-file /dev/stdout \
    -- ./bin/echo-rust-nostd.elf arg1 arg2

# Pass arguments and environment variables.
./bin/nanvixd.elf \
    -console-file /dev/stdout \
    -- ./bin/echo-rust-nostd.elf \
    "arg1 arg2;VAR1=foo VAR2=bar"

# Pass arguments, environment variables, and kernel arguments.
# Format: "<app args>;<env vars>;<kernel args>"
./bin/nanvixd.elf \
    -console-file /dev/stdout \
    -- ./bin/echo-rust-nostd.elf \
    "arg1 arg2;VAR1=foo;feature1 feature2"

HTTP Mode (for multi-application scenarios)

# Start nanvixd in HTTP mode.
NANVIX_HTTP_ADDR=127.0.0.1:8080
./bin/nanvixd.elf -http-addr $NANVIX_HTTP_ADDR

# Spawn an application via HTTP (in another terminal).
curl --silent \
    --header "Content-Type: application/json" \
    --header "X-NVX-Message-Type: NEW" \
    --request POST \
    --data '{"tenant_id":"foo",
             "app_name":"bar",
             "program":"./bin/hello-rust-nostd.elf",
             "program_args":""}' \
    http://${NANVIX_HTTP_ADDR}

Standalone UserVM Mode (expert/debugging)

./bin/uservm.elf \
    -kernel ./bin/kernel.elf \
    -initrd ./bin/hello-rust-nostd.elf \
    -standalone

Running on Windows

On Windows, nanvixd supports standalone interactive mode (no HTTP mode). Both nanvixd and the UserVM are built natively with the WHP backend:

# Run via nanvixd (recommended).
.\bin\nanvixd.exe -- .\bin\hello-rust-nostd.elf

You can also launch a run via z.ps1:

# Run with default options.
.\z.ps1 run

# Run with a custom guest binary.
.\z.ps1 run -- -program bin\hello-rust-nostd.elf

For low-level debugging, the standalone UserVM is still available:

.\bin\uservm.exe -kernel .\bin\kernel.elf -initrd .\bin\hello-rust-nostd.elf -standalone

Note: HTTP mode is Linux-only. On Windows, only standalone interactive mode via nanvixd is supported.

Creating a New Rust Application (no_std)

1. Create directory at src/user/<name>/.

2. Add Cargo.toml:

   [package]
   name = "<name>"
   version.workspace = true
   license-file.workspace = true
   authors.workspace = true
   edition.workspace = true
   
   [[bin]]
   name = "<name>"
   path = "src/main.rs"
   
   [dependencies]
   nvx = { workspace = true }
   sys = { workspace = true }
   syslog = { workspace = true }
   

3. Create src/main.rs:

   // Copyright(c) The Maintainers of Nanvix.
   // Licensed under the MIT License.
   
   #![no_std]
   #![no_main]
   
   extern crate alloc;
   
   // Application entry point.
   

4. Add to workspace members in root Cargo.toml.

5. Add to ALL_GUEST_APPLICATIONS in the Makefile.

Creating a New C Application

1. Create directory at src/user/<name>/.
2. Create a Makefile following the pattern in existing C applications.
3. Write source files using the Nanvix POSIX layer (#include <nanvix/...>).
4. The application links against libposix.a, libc.a, and the custom linker script at build/user/linker/x86/user.ld.

Logging

• Use RUST_LOG environment variable for nanvixd daemon-level logging.
• Guest-side logging uses the syslog crate (error!, warn!, info!, debug!, trace!).
• Console output defaults to logs/ directory; use -console-file /dev/stdout to redirect to terminal.