#2724 Issue closed: pxe boot with grub (from iso or plain)¶

Labels: enhancement, needs sponsorship, no-issue-activity

DEvil0000 opened issue at 2021-12-08 10:25:¶

• ReaR configuration files ("cat /etc/rear/site.conf" and/or "cat /etc/rear/local.conf"):
  PXE config expected to support grub bootloader (and maybe ISO targets) in the future:

OUTPUT=PXE
OUTPUT_PREFIX_PXE=$HOSTNAME
PXE_TFTP_PREFIX=$HOSTNAME.
#OUTPUT_URL=tftpbootfs
PXE_TFTP_URL=sshfs://user@172.200.200.1/tmp/test
PXE_CONFIG_URL=sshfs://user@172.200.200.1/tmp/test/
PXE_RECOVER_MODE="manual"
PXE_CREATE_LINKS="IP"
USB_BOOTLOADER=grub

Config used to generate the ISO used in the example later:

OUTPUT=ISO
OUTPUT_URL=sshfs://user@hostname.domain/tftp_path/iso/
ISO_PREFIX="recover-$HOSTNAME"
#just about users
CLONE_USERS=(root)
CLONE_GROUPS=(root)
CLONE_ALL_USERS_GROUPS="false"

• Grub config snippets
  grub config for MAC based include since grub feature_net_search_cfg is documented but not implemented :(
  (in addition I have a main file including all the others with source)

source /boot/grub/grub.cfg-$net_pxe_mac

grub snippet to boot normally from tftp:

menuentry "Relax-and-Recover PXE" --class gnu-linux --class gnu --class os {
    # root=tftp
    # prefix=(tftp)/boot/grub
    insmod gzio
    insmod progress
    echo 'Loading kernel ...'
    linux /linux/vmlinuz  selinux=0 
# is serial is used: console=ttyS0,115200
    echo 'Loading initial ramdisk ...'
    initrd /linux/initrd
}

grub snippet to boot from iso on tftp:

menuentry "Relax-and-Recover PXE ISO" { 
  # root=tftp
  # prefix=(tftp)/boot/grub
  echo "booting form network stored iso"
  echo "you have to be very patient..."
  insmod progress
  set isofile="/iso/recover-hostname.iso"
  loopback loop $isofile
  linux (loop)/isolinux/kernel iso_location=$isofile rw selinux=0
# is serial is used: console=ttyS0,115200
  initrd (loop)/isolinux/initrd.cgz
}

• dnsmasq example config:

# DNS port (default 53, disable with 0)
port=0
# Listen only on the specified interface
interface=eth0

# define the dhcp ip range and mode used
# Note: the interface must have IP from this subnet
dhcp-range=tag:red,172.200.200.3,172.200.200.10,12h

# set tags for mac
dhcp-mac=set:red,00:0d:b9:*:*:*
dhcp-mac=set:red,00:13:3b:*:*:*

# allow static dhcp for mac by vender
dhcp-host=00:0d:b9:*:*:*,set:red
dhcp-host=00:13:3b:*:*:*,set:red

# deny unknown clients
dhcp-ignore=tag:!known

# set tags based on arch
dhcp-match=set:bios,option:client-arch,0
dhcp-match=set:efi-x86_64,option:client-arch,7
dhcp-match=set:efi-x86_64,option:client-arch,9
#dhcp-match=set:efi-x86,option:client-arch,6

# assign boot bin path based on tags
dhcp-boot=tag:red,tag:bios,/boot/pxelinux/pxelinux.0
dhcp-boot=tag:red,tag:bios,/boot/grub/i386-pc/booti386.0
dhcp-boot=tag:red,tag:efi-x86_64,/boot/grub/x86_64-efi/bootx64.efi

# promt boot option
pxe-prompt="Press F8 for menu or proceed with default in", 10

# pxe boot options and config path offered
pxe-service=x86PC, "Boot from local disk"
pxe-service=tag:red,tag:bios,x86PC,"pxelinux",/boot/pxelinux/pxelinux
pxe-service=tag:red,tag:bios,x86PC,"grub legacy bios",/boot/grub/i386-pc/booti386
#pxe-service=tag:red,tag:bios,x86PC,"grub legacy bios",/boot/grub/
pxe-service=tag:red,tag:efi-x86_64,X86-64_EFI,"grub efi",/boot/grub/x86_64-efi/bootx64.efi

enable-tftp
tftp-root=/var/lib/tftpboot

log-queries
log-dhcp
#log-facility=/var/log/dnsmasq.log

• grub boot files needed (i386 in the example but works basically the same with efi on 64bit):
  generate bootloader with:

grub-mkimage -d /usr/lib/grub/i386-pc/ -O i386-pc-pxe -o /var/lib/tftpboot/boot/grub/i386-pc/booti386.0 -p '(tftp)/boot/grub' pxe tftp

you may need to copy over the mods by:

cp /usr/lib/grub/i386-pc/*  /var/lib/tftpboot/boot/grub/i386-pc

• Description of the issue (ideally so that others can reproduce it):

output=PXE does at the moment only support syslinux and not grub. This may be fine for most usecases with grub however I am more familier and you can actually use the shell. Also you get boot from ISO and other features for free.
At the moment I don't have the time to implement the grub config writing for PXE but I want to document the needed snippets here so someone else may do so.
I switched to output=ISO and provide the PXE config from somewhere else for the moment. That is more convinient and I can use the same ISO no matter if I actually put it on USB, TFTP or run it over IPMI.

additional notes:

• ISO on USB may replace current output=USB mode but can also used as some kind of RAW with ISO mode.
• grub can also use http (not sure about https) similar to tftp
• I am quite sure tftp/http could also be used in grub config without DHCP/PXE

gdha commented at 2021-12-23 08:55:¶

@DEvil0000 Would be a serious enhancement for Rear for sure. However, the amount of work to test all different Linux flavors is a nightmare IMHO.
Nothing prevents you to work on a PR and we would welcome it with open arms and assist you where we can.

github-actions commented at 2022-02-22 02:10:¶

Stale issue message

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[Export of Github issue for rear/rear.]