OpenWrt on HP Microserver Gen8

This was done when the server already had a working debian in its own partition. Can be done also in a new/empty disk using a live install disk.

• Download required files:
• rootfs image (e.g. https://downloads.openwrt.org/releases/19.07.5/targets/x86/64/openwrt-19.07.5-x86-64-rootfs-ext4.img.gz).
• kernel (e.g. https://downloads.openwrt.org/releases/19.07.5/targets/x86/64/openwrt-19.07.5-x86-64-vmlinuz).
• Network driver: kmod-libphy and kmod-tg3 (https://downloads.openwrt.org/releases/19.07.5/targets/x86/64/packages/kmod-libphy_4.14.209-1_x86_64.ipk and https://downloads.openwrt.org/releases/19.07.5/targets/x86/64/packages/kmod-tg3_4.14.209-1_x86_64.ipk).
• Prepare a partition for OpenWrt
• Copy image to hard disk partition with dd or similar tool.
• Copy kernel to /boot.
• Copy both ipk files for the network driver to /tmp.
• Install grub2 to the disk if not present already.
• Write a grub entry for OpenWrt, e.g. (modify partition location/id as needed):

menuentry 'OpenWrt 19.07.5 (on /dev/sdc2)' --class openwrt --class gnu-linux --class gnu --class os $menuentry_id_option 'osprober-gnulinux-simple-57f8f4bc-abf4-655f-bf67-946fc0f9f25b' {
    insmod part_msdos
    insmod ext2
    set root='hd2,msdos2'
    if [ x$feature_platform_search_hint = xy ]; then
        search --no-floppy --fs-uuid --set=root --hint-bios=hd2,msdos2 --hint-efi=hd2,msdos2 --hint-baremetal=ahci2,msdos2  57f8f4bc-abf4-655f-bf67-946fc0f9f25b
    else
        search --no-floppy --fs-uuid --set=root 57f8f4bc-abf4-655f-bf67-946fc0f9f25b
    fi
    linux /boot/vmlinuz root=/dev/sdc2
}

• Update-grub
• Boot
• opkg install /tmp/kmod-libphy... and opkg install /tmp/kmod-tg3
• Configure as needed
• Once you have internet connection consider install additional packages (e.g. nano, luci-admin-full).

OpenWRT: opening ports to the WAN (aka NAT, aka port forwarding)

Opening a port to a LAN computer is simple, you can do it from the GUI:

# Port 22422 -> 10.0.0.109:22422
config redirect
        option target 'DNAT'
        option src 'wan'
        option dest 'lan'
        option src_dport '22422'
        option dest_ip '10.0.0.109'
        option dest_port '22422'
        option proto 'tcp'
        option name 'Allow-SSH-bob' 

Opening a port to your router is not so simple:

# Port 64430 -> 10.0.0.1:443
config redirect
        option src 'wan'
        option proto 'tcp'
        option src_dport '64430'
        option dest_ip '10.0.0.1'
        option dest_port '443'
        option name 'Allow-HTTPS-router-redirect'

config rule
        option src 'wan'
        option proto 'tcp'
        option dest_port '443'
        option target 'ACCEPT'
        option name 'Allow-HTTPS-router-rule' 

Source:
http://www.smallbusinesstech.net/more-complicated-instructions/openwrt/setting-up-port-forwarding-and-dealing-with-loopbacks-on-openwrt-kamikaze-8.09.1