sortix-mirror/share/man/man7/release-iso-modification.7

.Dd February 5, 2018
.Dt RELEASE-ISO-MODIFICATION 7
.Os
.Sh NAME
.Nm release-iso-modification
.Nd instructions on how to modify release .iso filesystems
.Sh DESCRIPTION
This document describes how to modify Sortix .iso releases to meet your custom
needs.
The bootloader configuration in .iso releases is designed with an extensible
hooks system that let's you override it with further configuration and to load
additional files of your choice into the live environment.
The live environment is configurable through the normal operating system
configuration as described in section 5 of the manual.
.Pp
The release modification procedure lets you customize aspects such as the
default bootloader menu option and timeout, the default hostname, the default
keyboard layout, the default graphics resolution, adding files of your choice to
the live environment, control which drivers are loaded by default, control which
live environment daemons are started by default, deploy ssh keys so secure shell
connections are trusted on the first connection, and so on.
.Ss Prerequisites
.Bl -bullet -compact
.It
A
.Pa sortix-x.y-arch.iso
release for your architecture.
.It
.Xr xorriso 1
needs to be installed.
.El
.Ss Overview
The release modification process has three stages:
.Pp
.Bl -bullet -compact
.It
Optionally, creating additional files that will be loaded onto the live
environment (the liveconfig).
.It
Creating additional bootloader configuration (the bootconfig), which will
contain an archived copy of the liveconfig (if any).
.It
Adding the bootconfig to the release .iso.
.El
.Pp
The bootloader menu Install and Upgrade selections will start the live
environment and run the
.Xr sysinstall 8
installer and
.Xr sysupgrade 8
upgrader respectively and they are thus also customizable by this procedure.
.Ss Convenience Scripts
The release modification can be done manually by hand, or you can use the
following convenience scripts that make the release modification easy:
.Pp
.Bl -bullet -compact
.It
.Xr tix-iso-liveconfig 8
that generates additional configuration files for the live environment.
.It
.Xr tix-iso-bootconfig 8
that generates additional bootloader configuration and optionally configures the
bootloader to load the liveconfig into the live environment.
.It
.Xr tix-iso-add 8
that adds the bootconfig (and thus the liveconfig if any) to the release .iso.
.El
.Pp
These convenience scripts come with the operating system and are installed in
the
.Pa /sbin
directory.
These scripts are entirely for convenience and you can perform their tasks
yourself if they don't meet your needs.
The scripts are readable shell scripts and you can learn how they work and
extend them with your own features.
.Pp
If you are not on a Sortix system or on a different version of Sortix than the
one you are customizing, you can download the shell scripts matching the latest
stable release:
.Pp
.Bl -bullet -compact
.It
.Lk https://sortix.org/release/stable/scripts/tix-iso-liveconfig
.It
.Lk https://sortix.org/release/stable/scripts/tix-iso-bootconfig
.It
.Lk https://sortix.org/release/stable/scripts/tix-iso-add
.El
.Pp
If you are not customizing the latest stable release, you can find the matching
versions of the scripts in the
.Pa scripts/
subdirectory of the appropriate release directory, or you can check out the
.Pa tix
directory in the source code from
.Lk https://sortix.org/source/
matching the release you are currently customizing.
.Ss Additional Live Configuration Configuration
The live environment is a normal instance of the operating system and can be
configured by adding additional files or overwriting existing files.
Section 5 of the manual documents the system and software configuration files.
Additional files can also be added for their own sake.
.Pp
To do so, create a directory that will contain this additional live environment
configuration (liveconfig), whose contents will be extracted on top of the live
environment's root filesystem.
A compressed archive of this directory will be made in the next subsection and
needs to be registered with the bootloader configuration.
.Pp
The
.Xr tix-iso-liveconfig 8
convenience script is useful as it offers a lot of commonly useful
customizations to the live environment and can populate an initial liveconfig
directory for you.
.Ss Additional Bootloader Configuration
The GRUB bootloader configuration of an release .iso is extensible and allows
additional configuration to hook into it by writing a
.Pa /boot/grub/hooks.cfg
configuration file as described in
.Xr release-iso-bootconfig 7 .
.Pp
To do so, create a directory that will contain this additional bootloader
configuration (bootconfig), whose contents will be added onto the release .iso.
The liveconfig (if any) is normally added to the bootconfig as a compressed
archive and the additional bootloader configuration loads it as an initrd onto
the live environment.
The bootconfig will be overlaid to the release .iso in the next subsection.
.Pp
The
.Xr tix-iso-bootconfig 8
convenience script makes it easy to generate common additional bootloader
configuration and its documentation has examples of what it can do.
It is commonly used with the
.Fl \-liveconfig
option to generate the bootloader configuration that loads the additional files
from the liveconfig into the live environment.
.Ss Adding Files To The Release
Releases are modified by adding the bootconfig (which contains a compressed copy
of the liveconfig, if any) files to the release .iso.
.Pp
The
.Xr tix-iso-add 8
convenience script makes it easy to add files to a release .iso while taking
care to keep the release .iso bootable after the modification.
You need
.Xr xorriso 1
installed to use this script.
Alternatively you can add the files to the release .iso by running
.Xr xorriso 1
yourself:
.Bd -literal
xorriso \\
  -indev "$input_file" \\
  -outdev "$output_file" \\
  -boot_image grub keep \\
  -pathspecs on \\
  -add \\
  ="$input_directory"
.Ed
.Pp
Your modified release can then be used in place of the original release.
See the
.Sx EXAMPLES
section below for inspiration on what customizations to make, as well as the
manual pages for the
.Xr tix-iso-liveconfig 8
and
.Xr tix-iso-bootconfig 8
convenience scripts.
.Sh EXAMPLES
This section contains examples of how one can modify a release .iso.
.Ss "No Change"
To customize a release with no customizations except for the bootloader to say
the release was modified by the current user on the current host:
.Bd -literal
tix-iso-bootconfig bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Add Files to the Live Environment
To customize a release with additional files and directories in the live
environment:
.Bd -literal
mkdir -p liveconfig
mkdir -p liveconfig/root
echo foo > liveconfig/root/foofile
echo bar > liveconfig/root/barfile
tix-iso-bootconfig --liveconfig=liveconfig bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Provide Random Seed
To customize a release with a random seed
.Pa ( /boot/random.seed )
(which must be kept confidential and
not reused, see the warnings in
.Xr tix-iso-bootconfig 8 ) :
.Bd -literal
tix-iso-bootconfig --random-seed bootconfig
tix-iso-add sortix.iso bootconfig
rm bootconfig/boot/random.seed # When no longer useful.
rm sortix.iso # When no longer useful.
# And erase any media made from sortix.iso when no longer useful.
.Ed
.Ss Hostname, Keyboard Layout, and Graphics Resolution
To customize the live environment of a release with a custom hostname, custom
keyboard layout, and custom graphics resolution:
.Bd -literal
tix-iso-liveconfig \\
  --hostname=dragon \\
  --kblayout=dk \\
  --videomode=1920x1080x32 \\
  liveconfig
tix-iso-bootconfig --liveconfig=liveconfig bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Load Only Basic Ports by Default
To customize a release to only loads basic ports by default:
.Bd -literal
mkdir -p bootconfig/boot/grub
cat > bootconfig/boot/grub/hooks.cfg << EOF
select_ports_set_basic
EOF
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Default Bootloader Menu Option and Timeout
To customize a release so the default bootloader menu option is to run the
installer (bootloader menu option 1, counting from 0) and to change the
bootloader menu timeout to 2 seconds:
.Bd -literal
tix-iso-bootconfig --default=1 --timeout=2 bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Locked Down Multi-User Live Environment
To customize a release so the live environment boots to the login screen by
default with the provided database of users and groups
.Xr ( passwd 5
and
.Xr group 5 ) ,
password protect the
bootloader so only the default live environment option can be chosen by
unauthenticated users:
.Bd -literal
mkdir -p liveconfig/etc
# Each user's password is their username hashed with crypt_newhash(3).
(printf 'root:%s:0:0:root:/root:sh\\n' \\
        '$2b$10$S/fJmYIJSkRdifk61xDYn.w62y.vNu35tZkznR6xa3Ntg0hsbI8tO' &&
 printf 'alice:%s:1000:1000:alice:/home/alice:sh\\n' \\
        '$2b$10$4xGAf5FyCYedWoNltWvbmOOreXcI5cH/f4Jz/pkWrWxwZ7TQ/WbRC' &&
 printf 'bob:%s:1001:1001:bob:/home/bob:sh\\n' \\
        '$2b$10$0.IukhbHNy63te6ozVJ7Pu/EvbCcr892981XbqRQ0w16UPhmDdUqa') |
cat > liveconfig/etc/passwd
cat > liveconfig/etc/group << EOF
root::0:root
alice::1000:alice
bob::1001:bob
EOF
mkdir -p liveconfig/home
mkdir -p -m 700 liveconfig/home/alice
mkdir -p -m 700 liveconfig/home/bob
grub-mkpasswd-pbkdf2 | # enter bootloader password
tee /dev/tty |
tail -n 1 |
sed 's/PBKDF2 hash of your password is //' > liveconfig/etc/grubpw
tix-iso-bootconfig --liveconfig=liveconfig bootconfig
(echo 'insmod password_pbkdf2'
 echo 'set superusers="root"'
 echo "password_pbkdf2 root $(cat liveconfig/etc/grubpw)") |
cat >> bootconfig/boot/grub/hooks.cfg
cat > bootconfig/boot/grub/main.cfg << \EOF
menu_title="$base_menu_title"
hook_menu_pre
menuentry "Sortix $version" --unrestricted {
  load_sortix -- /sbin/init --target=multi-user
}
hook_menu_post
EOF
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Add a new Port
To customize a release with a new port
.Sy foo
in the
.Sy basic
and
.Sy all
port sets and fully integrate it with the bootloader menus:
.Bd -literal
mkdir -p bootconfig/boot/grub
cat > bootconfig/boot/grub/hooks.cfg << \\EOF
port_foo=true
tix_foo=false
export port_foo
export tix_foo
function hook_ports_menu {
  if $port_foo; then
    menuentry "foo = true" {
      port_foo=false
      configfile /boot/grub/ports.cfg
    }
  else
    menuentry "foo = false" {
      port_foo=true
      configfile /boot/grub/ports.cfg
    }
  fi
}
function hook_tix_menu {
  if $tix_foo; then
    menuentry "foo = true" {
      tix_foo=false
      configfile /boot/grub/tix.cfg
    }
  else
    menuentry "foo = false" {
      tix_foo=true
      configfile /boot/grub/tix.cfg
    }
  fi
}
function hook_ports_set_all {
  port_foo=true
}
function hook_tix_set_all {
  tix_foo=true
}
function hook_ports_set_basic {
  port_foo=true
}
function hook_tix_set_basic {
  tix_foo=true
}
function hook_ports_set_minimal {
  port_foo=false
}
function hook_tix_set_minimal {
  tix_foo=false
}
function hook_ports_set_no {
  port_foo=false
}
function hook_tix_set_no {
  tix_foo=false
}
function hook_ports_pre {
  if $tix_foo; then
    echo -n "Loading /repository/foo.tix.tar.xz (3.0M) ... "
    module --nounzip /repository/foo.tix.tar.xz \\
           --to /repository/foo.tix.tar.xz
    echo done
  fi
  if $port_foo; then
    echo -n "Loading /repository/foo.tix.tar.xz (3.0M) ... "
    module /repository/foo.tix.tar.xz --tix
    echo done
  fi
}
EOF
mkdir -p bootconfig/repository
cp foo.tix.tar.xz bootconfig/repository/foo.tix.tar.xz
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Add a new Ports Set
To customize a release with your own set of ports that are loaded by
default and fully integrate it with the bootloader menus:
.Bd -literal
mkdir -p bootconfig/boot/grub
cat > bootconfig/boot/grub/hooks.cfg << \\EOF
function hook_ports_menu_sets {
  menuentry "Load only recommended ports" {
    select_ports_set_recommended
    configfile /boot/grub/ports.cfg
  }
}
function hook_tix_menu_sets {
  menuentry "Load only basic binary packages" {
    select_tix_set_recommended
    configfile /boot/grub/tix.cfg
  }
}
select_ports_set_recommended {
  # The basic set can be extended by calling select_ports_set_basic here.
  port_foo=false
  port_bar=true
}
select_tix_set_recommended {
  # The basic set can be extended by calling select_tix_set_basic here.
  tix_foo=false
  tix_bar=true
}
# Load the recommended set of ports by default.
hook_ports_menu_sets
EOF
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Disable Networking Drivers By Default
To customize a release so it doesn't load network drivers by default, useful for
security reasons or to work around driver issues:
.Bd -literal
tix-iso-bootconfig --disable-network-drivers bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Disable DHCP Auto-Configuration By Default
To customize a release so
.Xr dhclient 8
doesn't automatically configure network interfaces using DHCP, useful if one
wants to manually configure network interfaces with
.Xr ifconfig 8 .
.Bd -literal
tix-iso-bootconfig --disable-dhclient bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss Enable SSH Server By Default
To customize a release so it starts the SSH server
.Xr sshd 8
automatically using the SSH configuration found in the liveconfig directory:
.Bd -literal
tix-iso-bootconfig --liveconfig=liveconfig --enable-sshd bootconfig
tix-iso-add sortix.iso bootconfig
.Ed
.Ss SSH Into Live Environment
To customize the live environment of a release so you can ssh into its root
user, to have the hostname
.Sy example.com ,
to start a ssh server with the keys generated now, authorize the local user to
ssh into the live environment's root user, and register the sshd server's keys
by their hostnames and network addresses so the connection is trusted on the
first attempt (you can omit the network addresses if you don't know yet):
.Bd -literal
tix-iso-liveconfig \\
  --hostname=example.com \\
  --root-ssh-authorized-keys="$HOME/.ssh/id_rsa.pub" \\
  --sshd-keygen \\
  --sshd-key-known-hosts-file="$HOME/.ssh/known_hosts" \\
  --sshd-key-known-hosts-hosts="example.com example.com,192.0.2.1 192.0.2.1" \\
  liveconfig
tix-iso-bootconfig --liveconfig=liveconfig --enable-sshd bootconfig
tix-iso-add sortix.iso bootconfig
rm -f liveconfig/etc/ssh_host_*_key # When no longer useful.
rm -f bootconfig/boot/liveconfig.xz # When no longer useful.
rm -f sortix.iso # When no longer useful.
# And erase any media made from sortix.iso when no longer useful.
ssh root@example.org # When the system is running.
.Ed
.Pp
This example generates sshd private keys (remember to delete them when no longer
needed, see the warnings in
.Xr tix-iso-liveconfig 8 )
and shows them by running:
.Bd -literal
mkdir -p liveconfig/etc
for keytype in rsa ecdsa ed25519; do
  ssh-keygen -t $keytype -f liveconfig/etc/ssh_host_${keytype}_key" -N "" \\
             -C "root@$hostname"
done
for keytype in rsa ecdsa ed25519; do
  ssh-keygen -l -f liveconfig/etc/ssh_host_${keytype}_key
done
.Ed
.Pp
It then constructs a
.Pa known_hosts
file for each network address and hashes it.
.Bd -literal
(for host in $network_addresses; do
  for keytype in rsa ecdsa ed25519; do
    printf '%s ' "$host" &&
    sed -E 's/^([^ ]* [^ ]*).*/\1/' \\
      liveconfig/etc/ssh_host_${keytype}_key.pub
  done
done) > known_hosts
ssh-keygen -H -f known_hosts
rm -f known_hosts.old
.Ed
.Pp
.Xr ssh 1
will trust the server by the network addresses on the first connection if you
append the contents of
.Pa known_hosts
to your
.Pa ~/.ssh/known_hosts .
.Pa liveconfig/root/.ssh/authorized_keys
file is made by appending the appropriate public keys previously made with
.Xr ssh-keygen 1 .
.Ss SSH Back From Live Environment
To customize the live environment of a release so its root user can ssh back to
your user, where the local hostname is
.Sy example.com
(the address to which the new installation will be connecting), by
generating a private key for the root user
(remember to delete it when no longer
needed, see the warnings in
.Xr tix-iso-liveconfig 8 )
and adding its public key to your local
.Pa ~/.ssh/authorized_keys :
.Bd -literal
tix-iso-liveconfig --root-ssh-keygen liveconfig
ssh-keyscan -H example.com > liveconfig/root/.ssh/known_hosts
cat liveconfig/root/.ssh/id_rsa.pub >> ~/.ssh/authorized_keys
tix-iso-bootconfig --liveconfig=liveconfig --enable-sshd bootconfig
tix-iso-add sortix.iso bootconfig
rm -f output-directory/root/.ssh/id_rsa # When no longer useful.
rm -f bootconfig/boot/liveconfig.xz # When no longer useful.
rm -f sortix.iso # When no longer useful.
# And erase any media made from sortix.iso when no longer useful.
.Ed
.Pp
This example will generate a ssh key for the root user by running:
.Bd -literal
mkdir -p -m 700 liveconfig/root/.ssh
ssh-keygen -t rsa -f liveconfig/root/.ssh/id_rsa -N "" -C "root@$hostname"
.Ed
.Pp
Consider omitting the
.Fl N
option and password protect the private key to protect it in the case of a leak.
.Sh SEE ALSO
.Xr xorriso 1 ,
.Xr development 7 ,
.Xr installation 7 ,
.Xr release-iso-bootconfig 7 ,
.Xr upgrade 7 ,
.Xr user-guide 7 ,
.Xr tix-iso-add 8 ,
.Xr tix-iso-bootconfig 8 ,
.Xr tix-iso-liveconfig 8