kernelbuilder

Free, open-source kernel builder as a service. Pick an upstream Linux kernel, toggle the options you need on top of a stock config (or upload your own), and download bzImage, vmlinux and the .config. Builds run on Cloudflare Containers with a shared compiler cache; an identical spec returns the existing artifact instantly.

1Kernel

2Architecture and base config

3Features

"default" keeps the base config's value (shown on the right once the base is resolved). "on"/"off" run scripts/config --enable/--disable followed by make olddefconfig; anything that can't be applied fails the job at the configure step, before compiling.

Sandboxing and isolation

setting	option	what it is	needs	default
default (off)onoff	USER_NS	User namespaces (rootless containers, bwrap, gVisor)		off
default (on)onoff	NET_NS	Network namespaces		on
default (on)onoff	PID_NS	PID namespaces		on
default (on)onoff	SECCOMP	seccomp		on
default (on)onoff	SECCOMP_FILTER	seccomp-bpf syscall filtering	SECCOMP	on
default (off)onoff	SECURITY_LANDLOCK	Landlock unprivileged sandboxing LSM		off
default (off)onoff	SECURITY_APPARMOR	AppArmor LSM		off
default (on)onoff	SECURITY_SELINUX	SELinux LSM		on
default (off)onoff	SECURITY_YAMA	Yama ptrace scope restrictions		off
default (off)onoff	CHECKPOINT_RESTORE	CRIU checkpoint/restore support		off
default (on)onoff	KEYS	Kernel keyring		on
default (on)onoff	AUDIT	Audit subsystem		on

cgroups and resource control

setting	option	what it is	needs	default
default (on)onoff	CGROUPS	Control groups		on
default (off)onoff	MEMCG	Memory cgroup	CGROUPS	off
default (on)onoff	CGROUP_PIDS	PID cgroup	CGROUPS	on
default (on)onoff	CGROUP_CPUACCT	CPU accounting cgroup	CGROUPS	on
default (off)onoff	CFS_BANDWIDTH	CPU bandwidth limits (cpu.max)	CGROUPS	off
default (on)onoff	BLK_CGROUP	Block I/O cgroup	CGROUPS	on
default (off)onoff	CGROUP_BPF	cgroup-attached BPF programs	BPF_SYSCALL, CGROUPS	off
default (on)onoff	CGROUP_FREEZER	cgroup freezer	CGROUPS	on
default (off)onoff	PSI	Pressure stall information		off

BPF and tracing

setting	option	what it is	needs	default
default (off)onoff	BPF_SYSCALL	bpf() syscall (eBPF programs/maps)		off
default (off)onoff	BPF_JIT	eBPF JIT compiler	BPF_SYSCALL	off
default (off)onoff	BPF_LSM	BPF LSM hooks	BPF_SYSCALL	off
default (off)onoff	BPF_UNPRIV_DEFAULT_OFF	Disable unprivileged bpf() by default	BPF_SYSCALL	off
default (off)onoff	DEBUG_INFO_BTF	BTF type info (needed for CO-RE / bpftrace)	DEBUG_INFO	off
default (on)onoff	KPROBES	kprobes		on
default (on)onoff	UPROBES	uprobes		on
default (on)onoff	FTRACE	ftrace framework		on
default (off)onoff	FUNCTION_TRACER	Function tracer	FTRACE	off
default (on)onoff	PERF_EVENTS	perf events		on

I/O and syscalls

setting	option	what it is	needs	default
default (on)onoff	IO_URING	io_uring		on
default (on)onoff	AIO	POSIX async I/O		on
default (off)onoff	USERFAULTFD	userfaultfd (live migration, lazy restore)		off
default (on)onoff	MEMFD_CREATE	memfd_create		on
default (on)onoff	EPOLL	epoll		on
default (off)onoff	TRANSPARENT_HUGEPAGE	Transparent huge pages		off
default (off)onoff	KSM	Kernel samepage merging		off
default (on)onoff	BINFMT_MISC	binfmt_misc (qemu-user, wasm loaders)		on
default (on)onoff	KEXEC	kexec		on

Filesystems

setting	option	what it is	needs	default
default (off)onoff	FUSE_FS	FUSE		off
default (off)onoff	VIRTIO_FS	virtiofs (FUSE over virtio)	FUSE_FS	off
default (off)onoff	OVERLAY_FS	OverlayFS		off
default (on)onoff	EXT4_FS	ext4		on
default (off)onoff	XFS_FS	XFS		off
default (off)onoff	BTRFS_FS	Btrfs		off
default (off)onoff	EROFS_FS	EROFS (read-only images)		off
default (off)onoff	SQUASHFS	SquashFS		off
default (on)onoff	ISO9660_FS	ISO 9660		on
default (on)onoff	VFAT_FS	VFAT		on
default (on)onoff	NFS_FS	NFS client		on
default (on)onoff	9P_FS	9P filesystem	NET_9P_VIRTIO	on
default (on)onoff	NET_9P_VIRTIO	9P over virtio transport	9P_FS	on
default (on)onoff	TMPFS_POSIX_ACL	tmpfs POSIX ACLs	TMPFS_XATTR	on
default (on)onoff	TMPFS_XATTR	tmpfs extended attributes		on
default (on)onoff	BLK_DEV_LOOP	Loop block device		on
default (off)onoff	BLK_DEV_NBD	Network block device		off
default (off)onoff	DM_CRYPT	dm-crypt		off
default (off)onoff	ZRAM	zram compressed RAM block device		off

Networking

setting	option	what it is	needs	default
default (off)onoff	TUN	TUN/TAP		off
default (off)onoff	VETH	veth pairs		off
default (off)onoff	BRIDGE	Ethernet bridging		off
default (off)onoff	MACVLAN	macvlan		off
default (off)onoff	VXLAN	VXLAN		off
default (on)onoff	NETFILTER	Netfilter framework		on
default (off)onoff	NF_TABLES	nftables	NETFILTER	off
default (on)onoff	IP_NF_IPTABLES	iptables (IPv4)	NETFILTER	on
default (on)onoff	NF_NAT	NAT	NETFILTER, NF_CONNTRACK	on
default (on)onoff	NF_CONNTRACK	Connection tracking	NETFILTER	on
default (on)onoff	IPV6	IPv6		on
default (off)onoff	WIREGUARD	WireGuard		off
default (off)onoff	UNIX_DIAG	Unix socket diagnostics (ss)		off
default (off)onoff	INET_DIAG	INET socket diagnostics (ss)		off
default (on)onoff	NET_SCHED	QoS / packet scheduling (tc)		on
default (off)onoff	VSOCKETS	AF_VSOCK		off
default (off)onoff	VIRTIO_VSOCKETS	virtio vsock transport	VSOCKETS	off
default (on)onoff	IP_PNP	Kernel IP autoconfiguration (ip= on cmdline)		on
default (on)onoff	IP_PNP_DHCP	DHCP during IP autoconfiguration	IP_PNP	on

Virtualization guest (KVM / Firecracker / Cloud Hypervisor)

setting	option	what it is	needs	default
default (on)onoff	KVM_GUEST	KVM guest support (kvmclock, PV features)		on
default (on)onoff	PVH	PVH boot entry in vmlinux (Firecracker / Cloud Hypervisor direct ELF boot); on by default here	PARAVIRT	on
default (on)onoff	PARAVIRT	Paravirtualization		on
default (off)onoff	VIRTIO_MMIO	virtio MMIO transport (Firecracker default)		off
default (off)onoff	VIRTIO_MMIO_CMDLINE_DEVICES	virtio MMIO devices from cmdline (legacy)	VIRTIO_MMIO	off
default (on)onoff	VIRTIO_PCI	virtio PCI transport		on
default (on)onoff	VIRTIO_BLK	virtio block		on
default (on)onoff	VIRTIO_NET	virtio net		on
default (on)onoff	VIRTIO_CONSOLE	virtio console		on
default (off)onoff	VIRTIO_BALLOON	virtio balloon		off
default (off)onoff	HW_RANDOM_VIRTIO	virtio RNG		off
default (on)onoff	PTP_1588_CLOCK_KVM	KVM PTP clock (chrony/phc)	KVM_GUEST	on
default (on)onoff	ACPI	ACPI		on
default (on)onoff	PCI	PCI (needed for ACPI boot on x86)		on
default (on)onoff	SERIAL_8250_CONSOLE	8250 serial console		on
default (on)onoff	BLK_DEV_INITRD	initrd / initramfs support		on
default (on)onoff	X86_MPPARSE	MPTable parsing (legacy Firecracker boot)		on
default (on)onoff	SERIO_I8042	i8042 (Firecracker clean shutdown)		on
default (on)onoff	KEYBOARD_ATKBD	AT keyboard (Firecracker clean shutdown)	SERIO_I8042	on
default (off)onoff	NVME_CORE	NVMe		off

Kernel features and size

setting	option	what it is	needs	default
default (on)onoff	MODULES	Loadable module support		on
default (off)onoff	IKCONFIG	Embed .config in kernel		off
default (off)onoff	IKCONFIG_PROC	Expose /proc/config.gz	IKCONFIG	off
default (on)onoff	PRINTK	printk		on
default (off)onoff	DEBUG_INFO	Debug info (large vmlinux)		off
default (on)onoff	SMP	SMP		on
default (on)onoff	NUMA	NUMA		on
default (on)onoff	X86_MSR	/dev/cpu/*/msr		on
default (on)onoff	CPU_ISOLATION	CPU isolation		on
default (off)onoff	PREEMPT	Preemptible kernel (low latency)		off
default (on)onoff	HZ_1000	1000 Hz tick		on
default (off)onoff	NO_HZ_FULL	Full dynticks		off
default (on)onoff	SCHEDSTATS	Scheduler statistics		on
default (on)onoff	TASKSTATS	Per-task statistics		on
default (on)onoff	DEVTMPFS	devtmpfs		on
default (on)onoff	DEVTMPFS_MOUNT	Auto-mount devtmpfs at /dev	DEVTMPFS	on

Any other option search all Kconfig symbols of the selected kernel

setting	option	what it is

Extra .config lines, one per line (e.g. CONFIG_CMDLINE="console=ttyS0"):

4Build

First build of a kernel version compiles everything (about 7-12 min on 4 cores); later builds of the same version reuse the built tree and only recompile what the changed options touch.

5Builds queue and history, newest first