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lorax - Man Page


lorax — Lorax Documentation


Brian C. Lane <bcl@redhat.com>

"I am the Lorax.  I speak for the trees [and images]."

The lorax tool is used to create the Anaconda installer boot.iso as well as the basic release tree, and .treeinfo metadata file. Its dependencies are fairly light-weight because it needs to be able to run in a mock chroot environment. It is best to run lorax from the same release as is being targeted because the templates may have release specific logic in them. eg. Use the rawhide version to build the boot.iso for rawhide, along with the rawhide repositories.

Lorax Cmdline Arguments

Create the Anaconda boot.iso

usage: lorax [-h] -p PRODUCT -v VERSION -r RELEASE [-s REPOSITORY] [--repo REPOSITORY] [-m REPOSITORY]
             [-t VARIANT] [-b URL] [--isfinal] [-c CONFIGFILE] [--proxy HOST] [-i PACKAGE] [-e PACKAGE]
             [--buildarch ARCH] [--volid VOLID] [--macboot] [--nomacboot] [--noupgrade]
             [--logfile LOGFILE] [--tmp TMP] [--cachedir CACHEDIR] [--workdir WORKDIR] [--force]
             [--add-template ADD_TEMPLATES] [--add-template-var ADD_TEMPLATE_VARS]
             [--add-arch-template ADD_ARCH_TEMPLATES] [--add-arch-template-var ADD_ARCH_TEMPLATE_VARS]
             [--noverify] [--sharedir SHAREDIR] [--enablerepo [repo]] [--disablerepo [repo]]
             [--rootfs-size ROOTFS_SIZE] [--noverifyssl] [--dnfplugin DNFPLUGINS] [--squashfs-only]
             [--skip-branding] [--dracut-conf DRACUT_CONF] [--dracut-arg DRACUT_ARGS] [-V]

Positional Arguments


Output directory

Named Arguments


show program's version number and exit

required arguments

-p,  --product

product name

-v,  --version

version identifier

-r,  --release

release information

-s,  --source

source repository (may be listed multiple times)

Default: []


source dnf repository file

Default: []

Named Arguments

-m,  --mirrorlist

mirrorlist repository (may be listed multiple times)

Default: []

-t,  --variant

variant name

Default: ""

-b,  --bugurl

bug reporting URL for the product

Default: "your distribution provided bug reporting tool"


Default: False

-c,  --config

config file

Default: "/etc/lorax/lorax.conf"


repo proxy url:port

-i,  --installpkgs

package glob to install before runtime-install.tmpl runs. (may be listed multiple times)

Default: []

-e,  --excludepkgs

package glob to remove before runtime-install.tmpl runs. (may be listed multiple times)

Default: []


build architecture


volume id


Make the iso bootable on UEFI based Mac systems

Default: True


Do not create a Mac bootable iso

Default: False


Default: True


Path to logfile

Default: ./lorax.log


Top level temporary directory

Default: "/var/tmp/lorax"


DNF cache directory. Default is a temporary dir.


Work directory, overrides --tmp. Default is a temporary dir under /var/tmp/lorax


Run even when the destination directory exists

Default: False


Additional template for runtime image

Default: []


Set variable for runtime image template

Default: []


Additional template for architecture-specific image

Default: []


Set variable for architecture-specific image

Default: []


Do not verify the install root

Default: True


Directory containing all the templates. Overrides config file sharedir


Names of repos to enable

Default: []


Names of repos to disable

Default: []


Size of root filesystem in GiB. Defaults to 2.

Default: 2


Do not verify SSL certificates

Default: False


Enable a DNF plugin by name/glob, or * to enable all of them.

Default: []


Use a plain squashfs filesystem for the runtime.

Default: False


Disable automatic branding package selection. Use --installpkgs to add custom branding.

Default: False

dracut arguments: (default: )


Path to a dracut.conf file to use instead of the default arguments. See the dracut.conf(5) manpage.


Argument to pass to dracut when rebuilding the initramfs. Pass this once for each argument. NOTE: this overrides the defaults.


Run this as root to create a boot.iso in ./results/:

dnf install lorax
setenforce 0
lorax -p Fedora -v 38 -r 38 \
-s http://dl.fedoraproject.org/pub/fedora/linux/releases/38/Everything/x86_64/os/ \
-s http://dl.fedoraproject.org/pub/fedora/linux/updates/38/Everything/x86_64/ \
setenforce 1

You can add your own repos with -s and packages with higher NVRs will override the ones in the distribution repositories.

Under ./results/ will be the release tree files: .discinfo, .treeinfo, everything that goes onto the boot.iso, the pxeboot directory, and the boot.iso under ./results/images/.


By default lorax will search for the first package that provides system-release that doesn't start with generic- and will install it. It then selects a corresponding logo package by using the first part of the system-release package and appending -logos to it. eg. fedora-release and fedora-logos.


If a variant is passed to lorax it will select a system-release package that ends with the variant name. eg. Passing --variant workstation will select the fedora-release-workstation package if it exists. It will select a logo package the same way it does for non-variants. eg. fedora-logos.

If there is no package ending with the variant name it will fall back to using the first non-generic package providing system-release.

Custom Branding

If --skip-branding is passed to lorax it will skip selecting the system-release, and logos packages and leave it up to the user to pass any branding related packages to lorax using --installpkgs. When using skip-branding you must make sure that you provide all of the expected files, otherwise Anaconda may not work as expected. See the contents of fedora-release and fedora-logos for examples of what to include.

Note that this does not prevent something else in the dependency tree from causing these packages to be included. Using --excludepkgs may help if they are unexpectedly included.

Running Inside of Mock

As of mock version 2.0 you no longer need to pass --old-chroot. You will, however, need to pass --enable-network so that the mock container can download packages.

Older versions of mock, between 1.3.4 and 2.0, will need to pass --old-chroot to mock. These versions of mock default to using systemd-nspawn which cannot create the needed loop device nodes. Passing --old-chroot will use the old system where /dev/loop* is setup for you.

How It Works

Lorax uses dnf to install packages into a temporary directory, sets up configuration files, it then removes unneeded files to save space, and creates a squashfs filesystem of the files.  The iso is then built using a generic initramfs and the kernel from the selected repositories.

To drive these processes Lorax uses a custom template system, based on Mako templates with the addition of custom commands (documented in pylorax.ltmpl.LoraxTemplateRunner). Mako supports %if/%endif blocks as well as free-form python code inside <% %> tags and variable substitution with ${}. The default templates are shipped with lorax in /usr/share/lorax/templates.d/99-generic/ and use the .tmpl extension.


The runtime-install.tmpl template lists packages to be installed using the installpkg command.  This template is fairly simple, installing common packages and architecture specific packages. It must end with the run_pkg_transaction command which tells dnf to download and install the packages.


The runtime-postinstall.tmpl template is where the system configuration happens. The installer environment is similar to a normal running system, but needs some special handling. Configuration files are setup, systemd is told to start the anaconda.target instead of a default system target, and a number of unneeded services are disabled, some of which can interfere with the installation. A number of template commands are used here:

  • append to add text to a file.
  • chmod changes the file's mode.
  • install to install a file into the installroot.
  • mkdir makes a new directory.
  • move to move a file into the installroot
  • replace does text substitution in a file
  • remove deletes a file
  • runcmd run arbitrary commands.
  • symlink creates a symlink
  • systemctl runs systemctl in the installroot


The runtime-cleanup.tmpl template is used to remove files that aren't strictly needed by the installation environment. In addition to the remove template command it uses:

  • removepkg remove all of a specific package's contents. A package may be pulled in as a dependency, but not really used. eg. sound support.
  • removefrom Removes some files from a package. A file glob can be used, or the --allbut option to remove everything except a select few.
  • removekmod Removes kernel modules

The squashfs filesystem

After runtime-*.tmpl templates have finished their work lorax creates an empty ext4 filesystem, copies the remaining files to it, and makes a squashfs filesystem of it. This file is the / of the boot.iso's installer environment and is what is in the LiveOS/squashfs.img file on the iso.

iso creation

The iso creation is handled by another set of templates. The one used depends on the architecture that the iso is being created for. They are also stored in /usr/share/lorax/templates.d/99-generic and are named after the arch, like x86.tmpl and aarch64.tmpl. They handle creation of the tree, copying configuration template files, configuration variable substitution, treeinfo metadata (via the treeinfo template command). Kernel and initrd are copied from the installroot to their final locations and then xorrisofs is run to create the boot.iso

Custom Templates

The default set of templates and configuration files from the lorax-generic-templates package are shipped in the /usr/share/lorax/templates.d/99-generic/ directory. You can make a copy of them and place them into another directory under templates.d and they will be used instead if their sort order is below all other directories. This allows multiple packages to ship lorax templates without conflict. You can (and probably should) select the specific template directory by passing --sharedir to lorax.


Weldr Team


Feb 07, 2024 40.5 Lorax