diff --git a/README.md b/README.md
index e44a878..479dbbf 100644
--- a/README.md
+++ b/README.md
@@ -8,8 +8,8 @@ Turning containers into bootable VMs
 # Build the container
 podman build ./example/alpine -t slim-alpine
 
-# Make the container bootable by extracing initrd and vmlinuz (initial ramdisk and kernel)
-slim build slim-alpine
+# Make the container bootable by extracing initrd (initial ramdisk)
+slim build qcow2 slim-alpine --init=/init
 
 # Boot the image using QEMU, `./example/alpine/init` will drop you into an interactive shell.
 slim run slim-alpine
diff --git a/example/alpine/init b/example/alpine/init
index 6166119..c29378f 100644
--- a/example/alpine/init
+++ b/example/alpine/init
@@ -11,7 +11,6 @@ mount -t sysfs sysfs /sys
 
 # Networking
 echo slim > /proc/sys/kernel/hostname
-modprobe virtio_net
 ip link set lo up 2>/dev/null
 ip link set eth0 up 2>/dev/null
 udhcpc -i eth0 -f -q # Get DHCP lease
diff --git a/example/archlinux/init b/example/archlinux/init
index b00d629..7529f57 100644
--- a/example/archlinux/init
+++ b/example/archlinux/init
@@ -8,7 +8,6 @@ mount -t sysfs sysfs /sys
 
 # Networking
 echo slim > /proc/sys/kernel/hostname
-modprobe virtio_net
 ip link set lo up 2>/dev/null
 ip link set eth0 up 2>/dev/null
 # udhcpc -i eth0 -f -q # Get DHCP lease
diff --git a/src/build.rs b/src/build.rs
index b758fda..af7d951 100644
--- a/src/build.rs
+++ b/src/build.rs
@@ -5,6 +5,7 @@ use anyhow::{Context, Result, bail};
 use clap::{Args, ValueEnum};
 use flate2::write::GzEncoder;
 use std::fs::{self, File};
+use std::io;
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use tempfile::NamedTempFile;
@@ -75,10 +76,11 @@ fn to_raw_ext4(dir: &Path) -> Result<NamedTempFile> {
         .parse()
         .context("failed to parse du output")?;
     let used = used_kb * 1024;
-    let mb = 1024 * 1024;
+    let gb = 1024 * 1024 * 1024;
     let size = used
         + (used / 10) // Add 10%
-        + 64 * mb; // Add some margin
+        // TODO: make configurable
+        + 64 * gb; // Add some spare capacity for activities
     let size = size.to_string();
 
     let raw_file = NamedTempFile::new()?;
@@ -124,33 +126,13 @@ fn build_qcow2(image: &str, mount_path: &Path) -> Result<()> {
 
 fn build_initrd(image: &str, mount_path: &Path) -> Result<()> {
     let mount_path = mount_path.to_str().context("mount path is not UTF-8")?;
-    let vmlinuz_src = format!("{mount_path}/vmlinuz");
-
-    // The rootless overlay mount only exists inside podman unshare's user
-    // namespace, so every read of the rootfs must run there; pipes still
-    // cross the namespace boundary.
-    let _has_kernel = cmd(&["podman", "unshare", "--", "test", "-f", &vmlinuz_src])
-        .context("Image missing required /vmlinuz. Place kernel at /vmlinuz in Containerfile.")?;
 
     let reg_dir = registry_dir(image)?;
     fs::create_dir_all(&reg_dir)?;
     println!("Registry: {}", reg_dir.display());
 
-    let vmlinuz_dst = reg_dir.join("vmlinuz");
-    cmd(&[
-        "podman",
-        "unshare",
-        "--",
-        "cp",
-        &vmlinuz_src,
-        vmlinuz_dst.to_str().context("registry path is not UTF-8")?,
-    ])
-    .context("Failed to copy vmlinuz out of the image mount")?;
-    println!("Copied vmlinuz -> {}", vmlinuz_dst.display());
-
-    // Pack the rootfs as a gzipped newc cpio archive; vmlinuz is excluded
-    // because QEMU loads the kernel separately via -kernel. The cpio
-    // pipeline runs inside the namespace, its stdout is compressed here.
+    // Pack the rootfs as a gzipped newc cpio archive. The cpio pipeline
+    // runs inside the namespace, its stdout is compressed here.
     let initrd_path = reg_dir.join("initrd");
     let script = r#"cd "$1" && find . -not -path ./vmlinuz | cpio -o -H newc"#;
     let mut cpio = Command::new("podman")
@@ -162,7 +144,7 @@ fn build_initrd(image: &str, mount_path: &Path) -> Result<()> {
     let initrd_file = File::create(&initrd_path).context("Failed to create initrd file")?;
     let mut encoder = GzEncoder::new(initrd_file, flate2::Compression::default());
     let cpio_stdout = cpio.stdout.take().context("cpio stdout was not piped")?;
-    let copied = std::io::copy(&mut std::io::BufReader::new(cpio_stdout), &mut encoder);
+    let copied = io::copy(&mut io::BufReader::new(cpio_stdout), &mut encoder);
     let stream_result = copied
         .and_then(move |_| encoder.finish().map(|_| ()))
         .context("Failed to write the gzipped initrd");