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netbooting_of_a_rhel_7.5_le_powervm_lpar_with_an_aix_nim_server

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Netbooting of a RHEL 7.5 LE PowerVM LPAR with an AIX NIM Server

For this example the following settings are assumed:

  • A HMC called hmc manages managed-system.
  • A LPAR named myrhel75le is already defined on managed-system.
    • All required network and storage adapters as well as disk storage have been created up front.
    • The designated IP address is 192.168.10.75/24.
  • The AIX NIM server nim has the IP address 192.168.10.10/24.
  • The network adapter used for netbooting has the following mac address: 96:0d:e1:c7:5b:03.
  • Access to the HMC hmc via password-less SSH is possible from a central system.
  • The Red Hat Kickstart file used for the installation is accessible through a web server (IP address 192.168.10.120/24) at this URL:
    http://<web-server>/RHEL_Kickstart/myrhel75le.ks


How to create a Red Hat Kickstart file is beyond the scope here, please check your RHEL documentation on how to do it!

This picture shows the example setup in detail:

1) Create the files for netbooting on a different RHEL LE system

[root@pkvm-le-rhel75 ~]$ grub2-mknetdir --net-directory=/var/lib/tftpboot
Netboot directory for powerpc-ieee1275 created. Configure your DHCP server to point to
/boot/grub2/powerpc-ieee1275/core.elf

2) Transfer the RHEL netboot infrastructure to the AIX NIM server

[root@pkvm-le-rhel75 ~]$ cd /var/lib/tftpboot
[root@pkvm-le-rhel75-nfs tftpboot]$ tar cf /tmp/rhel7u5le-bootptab.tar boot
[root@pkvm-le-rhel75-nfs tftpboot]$ scp /tmp/rhel7u5le-bootptab.tar root@nim:/tmp

3) Unpack the RHEL netboot infrastructure on the AIX NIM server

[root@nim ~]$ cd /tftpboot
[root@nim tftpboot]$ mkdir rhel7u5-le
[root@nim tftpboot]$ cd rhel7u5-le
[root@nim rhel7u5-le]$ tar xvpf /tmp/rhel7u5le-bootptab.tar

4) Create the entry in the /etc/bootptab file on the AIX NIM server

[root@nim ~]$ cat etc/bootptab:
# Legend:
# first field -- hostname (may be full domain name and probably should be)
# bf – bootfile
# ip -- host IP address
# ht -- hardware type
# ha -- hardware address
# sa -- server IP address to tftp bootfile from
# sm -- subnet mask
myrhel75le:bf=/tftpboot/myrhel75le:ip=192.168.10.75:ht=ethernet:ha=960DE1C75B03:sa=192.168.10.10:sm=255.255.255.0:

[root@nim ~]$ cd /tftpboot
[root@nim tftpboot]$ ln -s rhel7u5-le/boot/grub2/powerpc-ieee1275/core.elf myrhel75le
[root@nim tftpboot]$ ls -l myrhel75le
lrwxrwxrwx  1 root system 41 2017-10-06 14:45 myrhel75le -> ./rhel7u5-le/boot/grub2/powerpc-ieee1275/core.elf

6) Activate the bootp changes

As the bootp daemon runs under the control of the inetd daemon we have to notify the inetd to refresh its subsystems. 

[root@nim ~]$ refresh -s inetd
  • Unfortunately GRUB2 is not always working relatively to /tftpboot as “root” directory, therefore is it absolutely vital to set the following symbolic link:
[root@nim ~]$ cd /; ln -s /tftpboot/rhel7u5-le/boot /boot

Note:
The TFTP server on AIX does not chroot incoming clients into a specific directory by default.
Instead, access to the server is controlled by the /etc/tftpaccess.ctl file.

Make sure your /etc/tftpaccess.ctl file looks like this – or at least allows access to the /tftpboot and /boot directories: 

[root@nim ~]$ cat /etc/tftpaccess.ctl
# NIM access for network boot 
allow:/tftpboot 
allow:/boot

8) Create a customized GRUB2 grub.cfg file in /tftpboot

The naming for this customized grub.cfg file is grub.cfg-01-<MAC-ADDRESS> with <MAC-ADDRESS> coded as xx-yy-zz-aa-bb-cc. 

[root@nim ~]$ cat /tftpboot/grub.cfg-01-96-0d-e1-c7-5b-03
set default=0
set timeout=10

echo -e "\nWelcome to the Red Hat Enterprise Linux 7.5 LE installer!\n\n"

menuentry 'Red Hat Enterprise Linux 7.5 LE' {
  linux rhel7u5-le/vmlinuz ro ip=192.168.10.10::192.168.10.1:255.255.255.0:myrhel75le:eth0:none inst.ks=http://192.168.10.120:/RHEL_Kickstart/myrhel75le.ks
  initrd rhel7u5-le/initrd.img
}

If you don't want to use a customized GRUB2 grub.cfg file then you have to edit the /tftpboot/rhel75-le/boot/grub2/grub.cfg file. 

[root@nim ~]$ cat /tftpboot/rhel75-le/boot/grub2/grub.cfg
set default=0
set timeout=10

echo -e "\nWelcome to the Red Hat Enterprise Linux 7.5 LE installer!\n\n"

menuentry 'Red Hat Enterprise Linux 7.5 LE' {
  linux rhel7u5-le/vmlinuz ro ip=192.168.10.10::192.168.10.1:255.255.255.0:myrhel75le:eth0:none inst.ks=http://192.168.10.120:/RHEL_Kickstart/myrhel75le.ks
  initrd rhel7u5-le/initrd.img
}

In our example here the files /tftpboot/grub.cfg-01-96-0d-e1-c7-5b-03 and /tftpboot/rhel75-le/boot/grub2/grub.cfg are identical.

9) Copy the proper boot images into the right location

  • From the RHEL 7.5 LE DVD image – mounted under /mnt in this example – copy these files:
[root@nim ~]$ cp /mnt/ppc/ppc64/vmlinuz /tftpboot/rhel7u5-le/vmlinuz
[root@nim ~]$ cp /mnt/ppc/ppc64/initrd.img /tftpboot/rhel7u5-le/initrd.img
[root@nim ~]$ chmod 0644 /tftpboot/rhel7u5-le/*

10) Start the lpar_netboot command on the HMC

At last, initiate the installation from the central system via password-less SSH access of the HMC. 

[root@<central system> ~]$ ssh hscroot@<hmc> lpar_netboot -t ent -m 960DE1C75B03 -S <nim> -C 192.168.10.75 -K 255.255.255.0 -s auto -d auto -f -i -E LPAR_NETBOOT_DEBUG -T off myrhel75le <lpar_profile_of_myrhel75le> <managed-system>

After a while your Kickstart-automated RHEL installation should begin…

Using a Linux DHCP Server instead of the AIX NIM Server

  • The same steps as in the AIX NIM server scenario would be performed but a Linux DHCP server would be used instead of the AIX NIM server.
[root@<linux_dhcp> ~]$ cat /etc/dhcpd.conf
option domain-name "<your_domain_name_here>";
option domain-name-servers 192.168.10.8;   # DNS server IP address
option routers 192.168.10.1;
option ntp-servers 192.168.10.8;   # NTP server IP address
ddns-update-style none;
ignore unknown-clients;
allow bootp;
subnet 192.168.10.0 netmask 255.255.255.0 {
  range 192.168.10.100 192.168.10.250;
  default-lease-time 86400;
  max-lease-time 604800;
}
host myrhel75le {
  hardware ethernet 96:0D:E1:C7:5B:03;
  filename "myrhel75le";
  fixed-address 192.168.10.75;
  next-server 192.168.10.51;       # DHCP server IP address
}

GRUB2 sequence of TFTP requests for RHEL 7.5 LE

Using tcpdump and wireshark the following sequence of TFTP requests during the initial GRUB2 booting can be observed.

Client IP: 192.168.10.75 (= 0xC0A80A4B)
MAC address: 96:0D:E1:C7:5B:03 
  13   0.023061  192.168.10.75  192.168.10.10  TFTP   73  Read Request, File: /tftpboot/myrhel75le, Transfer type: octet
 642   7.548135  192.168.10.75  192.168.10.10  TFTP  111  Read Request, File: /boot/grub2/powerpc-ieee1275/normal.mod, Transfer type: octet, blksize=1024, tsize=0
 939   7.594158  192.168.10.75  192.168.10.10  TFTP  113  Read Request, File: /boot/grub2/powerpc-ieee1275/terminal.mod, Transfer type: octet, blksize=1024, tsize=0
 954   7.797228  192.168.10.75  192.168.10.10  TFTP  111  Read Request, File: /boot/grub2/powerpc-ieee1275/crypto.mod, Transfer type: octet, blksize=1024, tsize=0
 971   8.000194  192.168.10.75  192.168.10.10  TFTP  112  Read Request, File: /boot/grub2/powerpc-ieee1275/gettext.mod, Transfer type: octet, blksize=1024, tsize=0
 988   8.203462  192.168.10.75  192.168.10.10  TFTP  109  Read Request, File: /boot/grub2/powerpc-ieee1275/gzio.mod, Transfer type: octet, blksize=1024, tsize=0
1011   8.208153  192.168.10.75  192.168.10.10  TFTP  112  Read Request, File: //tftpboot/grub.cfg-01-96-0d-e1-c7-5b-03, Transfer type: octet, blksize=1024, tsize=0
1013   8.408127  192.168.10.75  192.168.10.10  TFTP  100  Read Request, File: //tftpboot/grub.cfg-C0A80A4B, Transfer type: octet, blksize=1024, tsize=0
1015   8.608099  192.168.10.75  192.168.10.10  TFTP   99  Read Request, File: //tftpboot/grub.cfg-C0A80A4, Transfer type: octet, blksize=1024, tsize=0
1017   9.021123  192.168.10.75  192.168.10.10  TFTP   98  Read Request, File: //tftpboot/grub.cfg-C0A80A, Transfer type: octet, blksize=1024, tsize=0
1019   9.221195  192.168.10.75  192.168.10.10  TFTP   97  Read Request, File: //tftpboot/grub.cfg-C0A80, Transfer type: octet, blksize=1024, tsize=0
1021   9.421168  192.168.10.75  192.168.10.10  TFTP   96  Read Request, File: //tftpboot/grub.cfg-C0A8, Transfer type: octet, blksize=1024, tsize=0
1023   9.621142  192.168.10.75  192.168.10.10  TFTP   95  Read Request, File: //tftpboot/grub.cfg-C0A, Transfer type: octet, blksize=1024, tsize=0
1025   9.821217  192.168.10.75  192.168.10.10  TFTP   94  Read Request, File: //tftpboot/grub.cfg-C0, Transfer type: octet, blksize=1024, tsize=0
1027  10.021184  192.168.10.75  192.168.10.10  TFTP   93  Read Request, File: //tftpboot/grub.cfg-C, Transfer type: octet, blksize=1024, tsize=0
1029  10.221159  192.168.10.75  192.168.10.10  TFTP  112  Read Request, File: //tftpboot/grub.cfg-01-96-0d-e1-c7-5b-03, Transfer type: octet, blksize=1024, tsize=0

RHEL will try to find (please note the hex-coded IP-address here: 192.168.10.75 = 0xC0A80A4B) in the following order: 

/tftpboot/grub.cfg-01-96-0d-e1-c7-5b-03
/tftpboot/grub.cfg-C0A80A4B
/tftpboot/grub.cfg-C0A80A4
/tftpboot/grub.cfg-C0A80A
/tftpboot/grub.cfg-C0A80
/tftpboot/grub.cfg-C0A8
/tftpboot/grub.cfg-C0A
/tftpboot/grub.cfg-C0
/tftpboot/grub.cfg-C
/tftpboot/grub.cfg-01-96-0d-e1-c7-5b-03

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