cli: Add --init to run/create (#1244)

Closes #1225

Add a flag to signify that we'd like to run a minimal init process that
can reap zombie processes. The actual support for this is in the
Containerization library so the plumbing here is very simple.

Author: dcantah

Package.resolved

@@ -23,7 +23,7 @@ import PackageDescription
 let releaseVersion = ProcessInfo.processInfo.environment["RELEASE_VERSION"] ?? "0.0.0"
 let gitCommit = ProcessInfo.processInfo.environment["GIT_COMMIT"] ?? "unspecified"
 let builderShimVersion = "0.8.0"
-let scVersion = "0.26.2"
+let scVersion = "0.26.3"
 
 let package = Package(
     name: "container",

Package.swift

@@ -51,6 +51,8 @@ public struct ContainerConfiguration: Sendable, Codable {
     public var ssh: Bool = false
     /// Whether to mount the rootfs as read-only.
     public var readOnly: Bool = false
+    /// Whether to use a minimal init process inside the container.
+    public var useInit: Bool = false
 
     enum CodingKeys: String, CodingKey {
         case id
@@ -70,6 +72,7 @@ public struct ContainerConfiguration: Sendable, Codable {
         case virtualization
         case ssh
         case readOnly
+        case useInit
     }
 
     /// Create a configuration from the supplied Decoder, initializing missing
@@ -100,6 +103,7 @@ public struct ContainerConfiguration: Sendable, Codable {
         virtualization = try container.decodeIfPresent(Bool.self, forKey: .virtualization) ?? false
         ssh = try container.decodeIfPresent(Bool.self, forKey: .ssh) ?? false
         readOnly = try container.decodeIfPresent(Bool.self, forKey: .readOnly) ?? false
+        useInit = try container.decodeIfPresent(Bool.self, forKey: .useInit) ?? false
     }
 
     public struct DNSConfiguration: Sendable, Codable {

Sources/ContainerResource/Container/ContainerConfiguration.swift

@@ -188,6 +188,7 @@ public struct Flags {
             runtime: String?,
             ssh: Bool,
             tmpFs: [String],
+            useInit: Bool,
             virtualization: Bool,
             volumes: [String]
         ) {
@@ -213,6 +214,7 @@ public struct Flags {
             self.runtime = runtime
             self.ssh = ssh
             self.tmpFs = tmpFs
+            self.useInit = useInit
             self.virtualization = virtualization
             self.volumes = volumes
         }
@@ -238,6 +240,15 @@ public struct Flags {
         )
         public var entrypoint: String?
 
+        @Flag(name: .customLong("init"), help: "Run an init process inside the container that forwards signals and reaps processes")
+        public var useInit = false
+
+        @Option(
+            name: .long,
+            help: .init("Use a custom init image instead of the default", valueName: "image")
+        )
+        public var initImage: String?
+
         @Option(
             name: .shortAndLong,
             help: .init("Set a custom kernel path", valueName: "path"),
@@ -248,12 +259,6 @@ public struct Flags {
         )
         public var kernel: String?
 
-        @Option(
-            name: .long,
-            help: .init("Use a custom init image instead of the default", valueName: "image")
-        )
-        public var initImage: String?
-
         @Option(name: [.short, .customLong("label")], help: "Add a key=value label to the container")
         public var labels: [String] = []
 
@@ -293,33 +298,33 @@ public struct Flags {
         )
         public var publishSockets: [String] = []
 
+        @Flag(name: .long, help: "Mount the container's root filesystem as read-only")
+        public var readOnly = false
+
         @Flag(name: [.customLong("rm"), .long], help: "Remove the container after it stops")
         public var remove = false
 
         @Flag(name: .long, help: "Enable Rosetta in the container")
         public var rosetta = false
 
+        @Option(name: .long, help: "Set the runtime handler for the container (default: container-runtime-linux)")
+        public var runtime: String?
+
         @Flag(name: .long, help: "Forward SSH agent socket to container")
         public var ssh = false
 
         @Option(name: .customLong("tmpfs"), help: "Add a tmpfs mount to the container at the given path")
         public var tmpFs: [String] = []
 
-        @Option(name: [.customLong("volume"), .short], help: "Bind mount a volume into the container")
-        public var volumes: [String] = []
-
         @Flag(
             name: .long,
             help:
                 "Expose virtualization capabilities to the container (requires host and guest support)"
         )
         public var virtualization: Bool = false
 
-        @Flag(name: .long, help: "Mount the container's root filesystem as read-only")
-        public var readOnly = false
-
-        @Option(name: .long, help: "Set the runtime handler for the container (default: container-runtime-linux)")
-        public var runtime: String?
+        @Option(name: [.customLong("volume"), .short], help: "Bind mount a volume into the container")
+        public var volumes: [String] = []
     }
 
     public struct Progress: ParsableArguments {

Sources/Services/ContainerAPIService/Client/Flags.swift

@@ -248,6 +248,7 @@ public struct Utility {
 
         config.ssh = management.ssh
         config.readOnly = management.readOnly
+        config.useInit = management.useInit
 
         if let runtime = management.runtime {
             config.runtimeHandler = runtime

Sources/Services/ContainerAPIService/Client/Utility.swift

@@ -842,6 +842,7 @@ public actor SandboxService {
         }
         // If the host doesn't support this, we'll throw on container creation.
         czConfig.virtualization = config.virtualization
+        czConfig.useInit = config.useInit
 
         for mount in config.mounts {
             if try mount.isSocket() {

Sources/Services/ContainerSandboxService/Server/SandboxService.swift

@@ -487,6 +487,74 @@ class TestCLIRunCommand2: CLITest {
             return
         }
     }
+
+    @Test func testRunCommandInit() throws {
+        do {
+            let name = getTestName()
+            try doLongRun(name: name, args: ["--init"])
+            defer {
+                try? doStop(name: name)
+            }
+            let inspectResp = try inspectContainer(name)
+            #expect(inspectResp.configuration.useInit == true, "expected useInit to be true in container configuration")
+
+            // With --init, PID 1 should be the init process, not "sleep".
+            var output = try doExec(name: name, cmd: ["cat", "/proc/1/cmdline"])
+            output = output.trimmingCharacters(in: .whitespacesAndNewlines)
+            #expect(
+                !output.hasPrefix("sleep"),
+                "expected PID 1 to be init process, not 'sleep', got '\(output)'"
+            )
+            try doStop(name: name)
+        } catch {
+            Issue.record("failed to run container with --init: \(error)")
+            return
+        }
+    }
+
+    @Test func testRunCommandInitReapsZombies() throws {
+        do {
+            let name = getTestName()
+            try doLongRun(name: name, args: ["--init"])
+            defer {
+                try? doStop(name: name)
+            }
+
+            _ = try doExec(
+                name: name,
+                cmd: [
+                    "sh", "-c",
+                    "sh -c 'sh -c \"exit 0\" &' && sleep 1",
+                ])
+
+            let psOutput = try doExec(name: name, cmd: ["sh", "-c", "ps aux | grep -c '\\[sh\\]' || true"])
+            let zombieCount = Int(psOutput.trimmingCharacters(in: .whitespacesAndNewlines)) ?? -1
+            #expect(
+                zombieCount == 0,
+                "expected no zombie processes with --init, found \(zombieCount)"
+            )
+            try doStop(name: name)
+        } catch {
+            Issue.record("failed to verify zombie reaping with --init: \(error)")
+            return
+        }
+    }
+
+    @Test func testRunCommandWithoutInitDefault() throws {
+        do {
+            let name = getTestName()
+            try doLongRun(name: name, args: [])
+            defer {
+                try? doStop(name: name)
+            }
+            let inspectResp = try inspectContainer(name)
+            #expect(inspectResp.configuration.useInit == false, "expected useInit to be false by default")
+            try doStop(name: name)
+        } catch {
+            Issue.record("failed to run container without --init: \(error)")
+            return
+        }
+    }
 }
 
 class TestCLIRunCommand3: CLITest {

Tests/CLITests/Subcommands/Run/TestCLIRunCommand.swift

@@ -50,6 +50,7 @@ container run [<options>] <image> [<arguments> ...]
 *   `--dns-option <option>`: DNS options
 *   `--dns-search <domain>`: DNS search domains
 *   `--entrypoint <cmd>`: Override the entrypoint of the image
+*   `--init`: Run an init process inside the container that forwards signals and reaps processes
 *   `--init-image <image>`: Use a custom init image instead of the default. This allows customizing boot-time behavior before the OCI container starts, such as running VM-level daemons, configuring eBPF filters, or debugging the init process.
 *   `-k, --kernel <path>`: Set a custom kernel path
 *   `-l, --label <label>`: Add a key=value label to the container
@@ -61,13 +62,14 @@ container run [<options>] <image> [<arguments> ...]
 *   `-p, --publish <spec>`: Publish a port from container to host (format: [host-ip:]host-port:container-port[/protocol])
 *   `--platform <platform>`: Platform for the image if it's multi-platform. This takes precedence over --os and --arch
 *   `--publish-socket <spec>`: Publish a socket from container to host (format: host_path:container_path)
+*   `--read-only`: Mount the container's root filesystem as read-only
 *   `--rm, --remove`: Remove the container after it stops
 *   `--rosetta`: Enable Rosetta in the container
+*   `--runtime`: Set the runtime handler for the container (default: container-runtime-linux)
 *   `--ssh`: Forward SSH agent socket to container
 *   `--tmpfs <tmpfs>`: Add a tmpfs mount to the container at the given path
 *   `-v, --volume <volume>`: Bind mount a volume into the container
 *   `--virtualization`: Expose virtualization capabilities to the container (requires host and guest support)
-*   `--runtime`: Set the runtime handler for the container (default: container-runtime-linux)
 
 **Registry Options**
 
@@ -104,6 +106,9 @@ container run -e NODE_ENV=production --cpus 2 --memory 1G node:18
 # run a container with a specific MAC address
 container run --network default,mac=02:42:ac:11:00:02 ubuntu:latest
 
+# run a container with an init process to reap zombies and forward signals
+container run --init ubuntu:latest my-app
+
 # run a container with a custom init image for boot customization
 container run --init-image local/custom-init:latest ubuntu:latest
 ```
@@ -205,6 +210,7 @@ container create [<options>] <image> [<arguments> ...]
 *   `--dns-option <option>`: DNS options
 *   `--dns-search <domain>`: DNS search domains
 *   `--entrypoint <cmd>`: Override the entrypoint of the image
+*   `--init`: Run an init process inside the container that forwards signals and reaps processes
 *   `--init-image <image>`: Use a custom init image instead of the default. This allows customizing boot-time behavior before the OCI container starts, such as running VM-level daemons, configuring eBPF filters, or debugging the init process.
 *   `-k, --kernel <path>`: Set a custom kernel path
 *   `-l, --label <label>`: Add a key=value label to the container
@@ -216,13 +222,14 @@ container create [<options>] <image> [<arguments> ...]
 *   `-p, --publish <spec>`: Publish a port from container to host (format: [host-ip:]host-port:container-port[/protocol])
 *   `--platform <platform>`: Platform for the image if it's multi-platform. This takes precedence over --os and --arch
 *   `--publish-socket <spec>`: Publish a socket from container to host (format: host_path:container_path)
+*   `--read-only`: Mount the container's root filesystem as read-only
 *   `--rm, --remove`: Remove the container after it stops
 *   `--rosetta`: Enable Rosetta in the container
+*   `--runtime`: Set the runtime handler for the container (default: container-runtime-linux)  
 *   `--ssh`: Forward SSH agent socket to container
 *   `--tmpfs <tmpfs>`: Add a tmpfs mount to the container at the given path
 *   `-v, --volume <volume>`: Bind mount a volume into the container
 *   `--virtualization`: Expose virtualization capabilities to the container (requires host and guest support)
-*   `--runtime`: Set the runtime handler for the container (default: container-runtime-linux)  
 
 **Registry Options**
 

docs/command-reference.md

@@ -497,6 +497,21 @@ container run --name nested-virtualization --virtualization --kernel /path/to/a/
 [    0.017893] kvm [1]: Hyp mode initialized successfully
 ```
 
+## Run a container with a provided init process
+
+By default, the command you specify in `container run` runs as PID 1 inside the container. This means it is responsible for reaping zombie processes and handling signals, which many applications are not designed to do. The `--init` flag runs a lightweight init process as PID 1 that automatically forwards signals and reaps orphaned child processes.
+
+```bash
+container run --init ubuntu:latest my-app
+```
+
+The init process is also available with `container create`:
+
+```bash
+container create --init --name my-container ubuntu:latest my-app
+container start my-container
+```
+
 ## Use a custom init image
 
 The `--init-image` flag allows you to specify a custom init filesystem image for the lightweight VM that runs your container. This enables: