2015/09/02

HP ILO VSP: CentOS 7/RHEL 7 Installation through Serial Console

Though it's feared or considered as outdated by some, command line tools (CLI) remain the right ones for many System Administration tasks. Among its countless advantages, there's tasks' automation through its Script-ability.
In this post, I'm willing to describe the Usage of HP ILO CLI utility for the Complete Installation of CentOS 7/RHEL 7 Distribution. Through this mean, one can complete a full System Installation from CLI. Such Installation are quite useful for many cases, like Remote Installation with low bandwidth, No need for  Advanced ILO license...
The Installation described below is a CentOS 7.1 System on Proliant G8 (using ILO4) and I'm leveraging on KickStart to automate its Install process. But, the same procedure can be easily adapted for other Linux Distributions.

Let's start by reviewing what is needed to complete that Installation:

1. Prerequisites:

  • ILO Configured with Valid IP Addressing parameters and reachable through SSH
  • Linux System (any distribution) with mkisofs installed
That Linux System will be used to build Custom CentOS/RHEL Image, in this case I'm using the System the same system to share the ISO mentioned below (Hostname: stivinstall; IP: 192.168.1.11)
  • OS Distribution Media (ISO) available on the network and reachable from the ILO
As said above, I'm installing CentOS 7.1, so I shared the ISO on an http server (installed and configured on my Linux System) and checked that it's well available (http://192.168.1.11/mnt/CentOS-7-x86_64-DVD-1503-01-text.iso)
  • (Optional) KickStart File for automated Installation
I'm leveraging on Kickstart to fully automate this Installation. But that is obviously optional. In this case, I made Kickstart file available on the same System where I hosted the OS ISO (http://192.168.1.11/dladc2-infpup01.ks)

2.  Modify CentOS 7 boot image to get output on Serial Console

By default, the boot ISO of RHEL 7/CentOS 7 will redirect its output to Graphical Console, so that needs to be modified to have Output directed to the Serial Console (VSP).

Mount the CentOS ISO on my elected Installation System (stivinstall)



The main directory we'll be modifying in this ISO is Isolinux, so Copy this directory under a temporarily writable directory.



As we're aiming to have everything in Text (console) mode, we should first get rid of graphical feature, like image. So, in the boot.msg, remove the ^Xsplash.lss line and delete the boot.cat (will be re-created later)



Now, the main and most important modifications are to add/edit two main configuration in the isolinux.cfg:

  1. A new line with "serial 1 9600" which indicates to IsoLinux to redirect the output to the Serial Console
  2. Append "console=ttyS1" to the Kernel Option (append initrd...). This is a kernel option that specifies what device to use as the primary console and its implies text as the Installation Mode.

Below, I've made use of diff between the modified and an unmodified isolinux.cfg to highlight that modifications. We can see that around Line 54 (this can obviously added as option in other place in the file), I added (the line starting with "#"is just a comment):

# Output to Serial Console ttyS1 - Stivesso
serial 1 9600


And for most of the append Kernel options (did this for Linux, Troubleshoot and Rescue Entries), I appended this at the end:
console=ttyS1



With that modification on isolinux.cfg completed, we can recreate the ISO. but first, we mount (with the --bind option) our modified directory under the isolinux directory of the mounted Image. Then, we can create the ISO using mkisofs.

Note that the volume ID (-V) of the ISO image must be the same as the inst.stage2= parameter in isolinux.cfg and replacing \x20 by a space (described in BZ#915563), Otherwise we'll be facing an Issue during the Installation and will be redirected to Dracut Emergency mode (... Warning: /dev/root does not exist, Entering emergency mode. Exit the shell to continue.)



The following is just a way to check that the created ISO has the needed modification in isolinux.cfg.



3.  Use ILO CLI to insert a virtual media

Once we've met the prerequisites listed above and created our modified ISO Image, we can go to the ILO (ssh) and insert the OS Distribution ISO in the ILO Virtual Media. This is done using the vm command, to see a full description of vm command options and syntax, one can use "help vm" as seen below



Get the Status of the CDROM Virtual Media,



Insert our OS Distribution ISO Image,



Connect the Inserted OS Image,



Set the system to boot on this image during the next reboot, for that we can either use boot_once to have it mounted and set as boot drive just during the next boot or boot_always to have it permanently mounted and set as boot drive.



4.  OS Installation:

Now that we have the media Inserted, we can proceed to the OS Installation by powering on the Server (or resetting if it was already running) and getting to VSP (Virtual Serial Port) to complete OS Installation.
I strongly advise to have the ILO SSH Console opened in max window size to make sure that the console output fit the size of the SSH console.



We'll get to the following nice screen,




Press Up (to make sure it’s at “Install CentOS 7” entry) and Tab,



From here, you can either just press enter to proceed to an Interactive Install, or if you prefer to use KickStart (as I do :-) ), then just enter the appropriate options. In this case, I’m entering the following inst.ks=http://192.168.1.10/stix-1.ks ip=192.168.1.11::192.168.1.1:255.255.255.0::ens2f0:none (more details about RHEL7/CentOS7 Kickstart Install in this post)
My suggestion for entering the option, "don't copy-paste, better write..."




References:

2 comments: