Added a minimal guide clarifying network-based installation

docs/user/guides/network.md

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+# Agama network-based installation
+
+The Agama installer ships as a Live ISO image generated by [KIWI NG](https://osinside.github.io/kiwi/index.html).
+
+It can be booted directly from an USB stick, CD/DVD or from the network using
+the initrd and the kernel extracted from the ISO as it is documented [by KIWI](https://osinside.github.io/kiwi/working_with_images/network_live_iso_boot.html#booting-a-live-iso-image-from-network).
+
+As the remote boot process of a live ISO image places the ISO file into a ramdisk
+by default it is recommended to also extract the compressed root file system
+(squashfs.img).
+
+Once extracted, these files must be copied to an appropriate location accessible
+via FTP, TFTP, HTTP, HTTPS...
+
+```bash
+sudo mount -oro,loop /srv/install/iso/agama-installer.iso /mnt
+sudo cp /mnt/boot/x86_64/loader/linux  /srv/tftpboot/boot/images/agama/x86_64/
+sudo cp /mnt/boot/x86_64/loader/initrd /srv/tftpboot/boot/images/agama/x86_64/
+sudo cp /mnt/LiveOS/squashfs.img /srv/tftpboot/boot/images/agama/x86_64/
+```
+
+How to set up a PXE server is out of scope of this guide but some documentation
+for SLES can be found at [PXE Server](#pxe-server-documentation).
+
+## Important changes compared to YaST installer
+
+There are some important changes that affect the installation workflow and
+specially the [kernel boot options](#kernel-boot-options).
+
+- Linuxrc is not included and [dracut][]. takes care of booting the installer.
+- NetworkManager is the default network backend.
+
+We tried to provide some [compatibility with Linuxrc options](https://agama-project.github.io/docs/user/reference/boot_options/linuxrc_compatibility)
+but we recommend migrating to [dracut][] specific ones because not all the use
+cases are supported.
+
+## Kernel boot options
+
+As there is no Linuxrc anymore, the options given as kernel parameters should
+be replaced by [dracut][] specific ones like the network configuration and the
+installer sources.
+
+For Agama specific options check the [boot options](https://agama-project.github.io/docs/user/reference/boot_options)
+section.
+
+### Specify the installer image location
+
+It already requires network configuration enforcing `rd.neednet=1`.
+
+- `root=live:http://192.168.0.1/boot/images/agama/x86_64/squashfs.img ip=dhcp`
+
+  Sets the SquashFS image or ISO to be fetched by the livenet [dracut][] module.
+
+- `inst.install_url=http://192.168.0.1/install/agama/x86_84`
+
+  Sets the repositories to be used by the installer instead of the defaults
+  repositories for the selected product. It is not necessary in case of an online
+  installation with a registered product.
+
+### Network configuration
+
+Network will be configured by [dracut][] only if really required so, there are
+some kernel boot options like `root=live:<URL>` that already requires or
+enforces the network to be configured, but not all the kernel options
+(e.g., `inst.install_url`, `ip`) do so, therefore, to ensure the network is
+configured by [dracut][] set `rd.neednet=1`.
+
+:::warning
+
+If explicit network configuration is provided using the `ip=` kernel boot option,
+Agama will disable the NetworkManager DHCP autosetup when starting the installer
+marking the NetworkManager connections generated by the nm-initrd-generator to
+be persisted after the installation by default.
+
+The `inst.copy_network=0` kernel boot option can be used to disable the copy of
+NetworkManager connections from `/etc/NetworkManager/system-connections` to the
+target system.
+
+:::
+
+### DHCP configuration
+
+- `ip=dhcp`
+
+  nm-initrd-generator will generate a profile using DHCP allowing multiple
+  devices to apply it at the same time.
+
+- `ip=enp1s0:dhcp`
+
+  The generated profile will be assigned to enp1s0 interface.
+
+- `ip=aa-bb-cc-dd-ee-ff:dhcp`
+
+  The generated profile will be assigned to the device with the specified mac address
+
+### DHCP static configuration
+
+- `ip=<client-IP>:[<peer>]:<gateway-IP>:<netmask>:<client_hostname>:<interface>:{none|off|dhcp|on|any|dhcp6|auto6|ibft}[:[<dns1>][:<dns2>]]`
+
+- `ip=10.144.136.45::10.144.136.254:24:agama1.suse.cz:enc800`
+
+  Static configuration using a prefix length as the netmask.
+
+- `ip=192.168.100.228::192.168.100.1:255.255.255.0:agama.test:aa-bb-cc-dd-ee-ff`
+
+  The interface can be also a mac address.
+
+### Use custom interface naming
+
+- `ifname=<interface>:<MAC>`
+
+  Assign network device name `<interface>` to the NIC with the MAC `<MAC>`.
+
+- `ifname=bootnet:AA:BB:CC:DD:EE:FF ip=bootnet:dhcp rd.neednet=1`
+
+  :::warning
+
+  Agama will persist the renaming of the interface after the installation
+  through a systemd network link file (e.g., `/etc/systemd/network/10-agama-ifname-bootnet.link`).
+
+  The file can be removed using a [post-installation script](/docs/user/reference/profile/scripts.md#post-installation-scripts)
+  at the Agama configuration.
+
+  :::
+
+## PXE server documentation
+
+For more information about setting up a PXE Boot Server on SUSE Linux
+Enterprise Server 16.0 refer to [this guide](https://susedoc.github.io/doc-modular/main/html/SLES-PXE-server/).
+
+[dracut]: https://man7.org/linux/man-pages/man7/dracut.cmdline.7.html