Building clusters with UmVirt Linux From Scratch

Configuring FreeDos raw disk image PXE boot over iSCSI

Prepare freedos disk image

Create 100MB raw disk image "freedos.img"
Install FreeDOS on it using QEMU
Upload it on PXE-server on /sources/iscsi directory

PXE-server kernel configuration

First of all iSCSI specific options have to be enabled in kernel:

    Device Drivers > 
      SCSI device support > 
         SCSI low-level drivers

    <M> iSCSI Initiator over TCP/IP [ISCSI_TCP]
    <M> iSCSI Boot Sysfs Interface  [ISCSI_BOOT_SYSFS]

    File systems >
      Pseudo filesystems

    <M>  Userspace-driven configuration filesystem  [CONFIGFS_FS]

    Device Drivers

    <M> Generic Target Core Mod (TCM) and ConfigFS Infrastructure ---> [TARGET_CORE]
       <M> TCM/IBLOCK Subsystem Plugin for Linux/BLOCK [TCM_IBLOCK]
       <M> TCM/FILEIO Subsystem Plugin for Linux/VFS [TCM_FILEIO]
       <M> TCM/pSCSI Subsystem Plugin for Linux/SCSI [TCM_PSCSI]
       <M> TCM/USER Subsystem Plugin for Linux [TCM_USER2]
       <M> TCM Virtual SAS target and Linux/SCSI LDD fabric loopback module [LOOPBACK_TARGET]
       <M> SCSI Target Mode Stack [ISCSI_TARGET]
       <M>    Chelsio iSCSI target offload driver [ISCSI_TARGET_CXGB4]
       <M> TCM Virtual Remote target [REMOTE_TARGET]

Linux kernel source tree is stored in "/usr/src/linux-*" directory.

To edit kerel options run

    make menuconfig

To build kernel run

    chimp kernel_build

To install kernel run

    chimp kernel_install

After kernel installation system should be rebooted.

PXE-server configuration

Enable and start iscsid service

systemctl enable iscsid
systemctl start iscsid

Install targetcli-ng package
If needed rebuild kernel to run iscsid and targetcli

iSCSI target configuration

open targetcli.

create link to file

cd backstores/fileio
create dos /sources/iscsi/freedos.img

create portal

cd /iscsi
create iqn.2025-08.com.umvirt.nas:freedos

create LUN

cd /iscsi/iqn.2025-08.com.umvirt.nas:freedos/tpg1/luns
create /backstores/fileio/dos

create acl

cd ../acls
create iqn.2025-08.com.umvirt.pxe

disable authentication

cd /iscsi/iqn.2025-08.com.umvirt.nas:freedos/tpg1/acls/iqn.2025-08.com.umvirt.pxe
set attribute authentication=0

save
```
cd /
saveconfig
```
exit
```
exit
```

iPXE configuration

create text file "freedos" in /srv/tftp directory:

#!ipxe
set initiator-iqn iqn.2025-08.com.umvirt.pxe
sanhook --drive 0x80  iscsi:192.168.180.254:6:3260:0:iqn.2025-08.com.umvirt.nas:freedos
sanboot --drive 0x80

Kea configuration

open /etc/kea/kea-dhcp4.conf.
replace "boot-file-name" value to "freedos"
```
"boot-file-name": "freedos"
```
restart Kea dhcp4 server
```
systemctl restart kea-dhcp4-server
```

Compute unit test launch

Run compute unit. On PXE boot attempt FreeDOS shold be loaded.

FreeDOS over iSCSI