.\" SPDX-License-Identifier: AGPL-3.0-or-later .\" Copyright (c) 2022 Red Hat GmbH .\" Author: Stefano Brivio .TH mbuto 1 .SH NAME .B mbuto \- Host-agnostic initramfs image builder for lightweight virtual machines .SH SYNOPSIS .B mbuto [\fIOPTIONS\fR\fB] [\fIADD_ON\fR\fB]... .SH DESCRIPTION .B mbuto \fR(\fIM\fRinimal \fIB\fRuilder \fIU\fRsing \fIT\fRerse \fIO\fRptions) builds Linux initramfs images suitable for lightweight virtual machine environments, without relying on distribution-specific tools (such as \fBdracut\fR(8), \fBdebootstrap\fR(8), \fBmkinitramfs\fR(8), etc.) or containerised environments. Programs are sourced from the host, together with required dynamic libraries. Kernel modules, links, and initial device nodes are configured manually. A convenience support for distribution packages is supplied, with the sole function of extracting packages, ignoring dependencies, without an actual installation process. For pre-defined profiles covering common tasks and use cases, see \fBPROFILES\fR. \fIADD_ON\fR can be a list of additional programs, kernel module names, device nodes, or generic files. The type is auto-detected. .SH OPTIONS .TP .BR \-c " " \fIgzip\fR|\fIlz4\fR|\fIlzma\fR|\fIauto\fR|\fInone\fR Compression method for CPIO file: \fIauto\fR picks the method resulting in the shortest decompression time, measured on the output image (average of five runs). Default is \fInone\fR. .TP .BR \-d Do not strip binary objects. By default, debugging information is stripped from copied binary objects. .TP .BR \-f " " \fIpath Path for initramfs output. By default, a temporary file is created. If the initramfs image already exists, add the given \fIADD_ON\fR to it. .TP .BR \-k " " \fIversion Installed kernel version to source associated modules from. By default, the currently running kernel version (as reported by uname(1)) is used. .TP .BR \-m " " \fIpath Relative root directory for \fI/lib/modules\fR. Default: / .TP .BR \-p " " \fIprofile Profile for add-ons, specific init script and format of printed command result. Can be one of \fIbase\fR, \fIbash\fR, \fIkata\fR, \fIkata_debug\fR, \fIpasst\fR, \fIkselftests\fR. See \fBPROFILES\fR below for further details. .TP .BR \-s " " \fIscript\fR|\fI-\fR Path to fix-up script to run before init, which can be used to replace the one defined by the profile. \fI-\fR disables the pre-init fix-up script. .TP .BR \-v Enable verbose operation. .TP .BR \-h Display help message with usage and options. .SH ENVIRONMENTAL VARIABLES Environmental variables can be used to replace: .TP .BR \fBPROGS\fI Base programs, to be included in the image, defined by the profile. .BR \fBLIBS_DLOPEN\fI Additional libraries, not directly linked from programs, typically loaded via dlopen(3) by matching libraries, in the form: \fBMATCHING_LIBRARY\fR \fBADDITIONAL_LIBRARY\fI .TP .BR \fBKMODS\fI Base kernel modules, defined by the profile. .TP .BR \fBNODES\fI Device nodes, copied from host if just the name is given, and created otherwise if in the form: \fBNAME\fR,\fBTYPE\fR,\fBMAJOR\fR,\fBMINOR .TP .BR \fBLINKS\fI Link to programs by name, as space-separated pairs of: \fBPROGRAM\fR \fBPATH\fR .TP .BR \fBDIRS\fI List of initial set of empty directories .TP .BR \fBCOPIES\fI Lists of paths to be copied, recursively, preserving attributes and parents. .SH PROFILES Profiles define sets of base programs, links, kernel modules, and pre-init scripts to cover common use cases. These profiles are currently available: .TP .BR \fBbase\fI The bare minimum to start an interactive shell. .TP .BR \fBbash\fI Start bash with a few kernel modules and tools to enable basic filesystem usage and networking configuration. .TP .BR \fBkata\fI Creates a guest image suitable for usage with Kata Containers (https://katacontainers.io): source \fIkata-agent\fR and perform cgroup setup in pre-init. .TP .BR \fBkata_debug\fI Creates a guest image intented to debug issues with Kata Containers (https://katacontainers.io): include some more utilities on top of the ones sourced by the \fIkata\fR profile, and starts an interactive shell before starting \fIkata-agent\fR. .TP .BR \fBpasst\fI Creates a guest image used to run the test suite of \fBpasst\fR(1) (https://passt.top), including a number of networking utilities among others. .TP .BR \fBkselftests\fI Creates a guest image including a set of Linux kernel selftests (https://kselftest.wiki.kernel.org/) together with the tools needed to run them. Modules and test programs are selected depending on the given test collections, and, for convenience, this profile also triggers installation of modules and test programs to temporary directories. The following sub-options are provided: .RS .TP .BR \-L List available collections. .TP .BR \-C " " \fIcollection\fR Select a collection of tests to run. Collections are defined by the set of targets in \fBtools/testing/selftests/Makefile\fR of the Linux kernel tree. .TP .BR \-T " " \fIcollection\fR:\fItest\fR Select a specific test to run, within a collection. Available tests are listed by \fITEST_PROGS\fR variables in the Makefile of a test subdirectory. .RE .SH EXAMPLES .TP .BR "Build a base image as temporary file" .RS .nf $ mbuto Applying profile base Creating image: /tmp/tmp.hbRUmHpR3a Size: bin 353k lib 4.0M kmod 213k total 4.6M compressed 4.5M /tmp/tmp.hbRUmHpR3a .fi .RE .TP .BR "Build a base image including grep and needed libraries" .RS .nf $ mbuto grep Applying profile base Creating image: /tmp/tmp.RXC8K7altF Size: bin 562k lib 4.0M kmod 213k total 4.8M compressed 4.7M /tmp/tmp.RXC8K7altF .fi .RE .TP .BR "Run an interactive shell with \fBqemu\fR(1)" .RS .nf $ kvm -kernel /boot/vmlinuz-$(uname -r) -initrd $(mbuto) \\ -nodefaults -nographic -append console=ttyS0 -serial stdio .fi .RE .TP .BR "Run the " \fItimens\fR " kselftests collection" .RS .nf $ cd linux $ kvm -kernel arch/x86/boot/bzImage \\ -initrd $(mbuto -p kselftests -C timens) \\ -nodefaults -nographic -append console=ttyS0 -serial stdio .fi .RE .TP .BR "Run the " \fIrtcpie\fR " kselftest from the " \fItimers\fR " collection" .RS .nf $ cd linux $ mbuto -p kselftests -T timers.rtcpie -f test.img $ kvm -kernel arch/x86/boot/bzImage -initrd test.img \\ -nodefaults -nographic -append console=ttyS0 -serial stdio .fi .RE .SH AUTHORS Stefano Brivio , Sevinj Aghayeva .SH REPORTING BUGS Please send reports or patches via e-mail to the authors. .SH COPYRIGHT Copyright (c) 2020-2022 Red Hat GmbH. \fBmbuto\fR is free software: you can redistribute it and/or modify it under the terms of the GNU Affero General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version. .SH SEE ALSO \fBqemu\fR(1), \fBsupermin\fR(1), \fBdracut\fR(8), \fBmkinitramfs\fR(8), \fBdebootstrap\fR(8). See example terminal captures at https://mbuto.sh.