Debian preseed example (old)

While informative, this is an old page (which you can see from its reference to Debian Buster).

1. Require a web server accessible from the host-to-set-up
2. Require a copy of the Debian [Buster] install CD/DVD (on USB?)
3. Require a DHCP server configured to give the host-to-set-up its IP address/mask/gateway/DNS servers, etc.
4. Boot from install media
5. At install menu, press <ESC>
6. At prompt, enter: auto url=http://192.168.100.1/basic.cfg and press <RETURN>
7. Sit back and glory in a job well done

See Debian: Automating the installation using preseeding

basic.cfg

d-i debian-installer/locale                                     string en_AU

d-i keyboard-configuration/xkb-keymap                           select us

d-i netcfg/choose_interface                                     select auto
d-i netcfg/get_hostname                                         string unassigned-hostname
d-i netcfg/get_domain                                           string unassigned-domain
d-i netcfg/wireless_wep                                         string

d-i mirror/country                                              string manual
d-i mirror/http/hostname                                        string deb.debian.org
d-i mirror/http/directory                                       string /debian
d-i mirror/http/proxy                                           string

d-i clock-setup/utc                                             boolean true
d-i time/zone                                                   string Australia/Sydney
d-i clock-setup/ntp                                             boolean true

d-i pkgsel/include                                              string cfengine3 openssh-server

d-i passwd/make-user                                            boolean false
d-i passwd/root-password-crypted                                password $6$VcS7ybrq3LtM1INK$TstQLYccguE5jLFKjI7CkW9wf7hWgx6XkI.3lSpOj.NcgzY5FHaC2Ffl2e9pY/ZdIL8ffo1zP7QYAG6IIg82r0

d-i partman-auto/method                                         string regular
d-i partman-auto/expert_recipe string                           \
        boot-root ::                                            \
                500 1000 1000 ext4                              \
                        $primary{ } $bootable{ }                \
                        method{ format } format{ }              \
                        use_filesystem{ } filesystem{ ext4 }    \
                        mountpoint{ /boot }                     \
                .                                               \
                5000 10000 1000000000 ext4                      \
                        $primary{ }                             \
                        method{ format } format{ }              \
                        use_filesystem{ } filesystem{ ext4 }    \
                        mountpoint{ / }                         \
                .                                               \
                1000 1000 1000 linux-swap                       \
                        $primary{ }                             \
                        method{ swap } format{ }                \
                .
d-i partman-partitioning/confirm_write_new_label                boolean true
d-i partman/choose_partition                                    select finish
d-i partman/confirm boolean                                     true
d-i partman/confirm_nooverwrite                                 boolean true

# 1 - Remove cfengine's "default" inputs and masterfiles subdirectories
# 2 - Create new, empty ones
# 3 - Edit the default settings for cfengine so that cf-execd will start
# 4 - Edit the kernel command line in grub so we get "eth0"-style naming instead of "ens4"-style
# 5 - Re-generate the configuration file used by grub at boot time
# 6 - Rename the network interface already configured by the installer in /etc/network/interfaces
# 7 - Configure cf-agent (cfengine) to point to our configuration hub

d-i preseed/late_command string                                                                                         \
        in-target rm -fr /var/lib/cfengine3/inputs /var/lib/cfengine3/masterfiles;                                      \
        in-target mkdir /var/lib/cfengine3/inputs /var/lib/cfengine3/masterfiles;                                       \
        in-target sed -i.backup -e 's/^RUN_CFEXECD=0$/RUN_CFEXECD=1/' /etc/default/cfengine3;                           \
        in-target sed -i.backup -e 's/quiet/quiet biosdevname=0 net.ifnames=0 ipv6.disable=1/' /etc/default/grub;       \
        in-target grub-mkconfig -o /boot/grub/grub.cfg;                                                                 \
        in-target sed -i.backup -e 's/ [ep][a-z0-9_]*[0-9]/ eth0/' /etc/network/interfaces;                             \
        in-target cf-agent -B 10.197.85.13

d-i grub-installer/only_debian                                  boolean true
d-i grub-installer/with_other_os                                boolean true
d-i grub-installer/bootdev                                      string /dev/vda

d-i finish-install/reboot_in_progress note