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AIX dual boot

  • 1.  AIX dual boot

    Posted Mon January 18, 2021 12:04 PM
    Client wants to do dual boot for different versions of AIX without virtualization/HMC. Like suppose he has 1 partition with 2 disks. In 1 disk he install AIX 7.1 and in other disk he install AIX 7.2. Now he will boot AIX 7.1 sometime and AIX 7.2 in some other time. Is this possible and is there any limitation or restrictions? Also the configuration does not currently include a DVD drive. Would they be able to install AIX from a USB drive and avoid the need for the DVD drive in the configuration ?

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    Nilabja Haldar
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  • 2.  RE: AIX dual boot

    Posted Tue January 19, 2021 01:07 AM
    This is possible.  Look up the topic "alternate disk install'. It's not really intended for this specific use case,  but you can use it that way.


  • 3.  RE: AIX dual boot

    Posted Tue January 19, 2021 02:35 AM

    Starting system management services without an HMC
    To get a boot console, you have to access the ASMI, see
    What is Service Processor And How To Access It
    ASMI (Advanced System Management Interface)

    If you have access to the console of the LPAR, you start the LPAR and while the "IBM IBM IBM" messages are displayed,
    you hit the 1 on the keyboard to access the SMS menu.
    The SMS menu is the BIOS of the LPAR, here you can select your boot device.
    Example Using SMS To Choose Boot Device

    Installation from USB see
    https://www.ibm.com/support/knowledgecenter/ssw_aix_71/rnbase715/rnbase715.html

    Chapter "Installing AIX using a USB flash memory stick"



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    Achim Haag
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  • 4.  RE: AIX dual boot

    Posted Tue January 19, 2021 02:54 AM
    Yes, it's possible.
    No limitations, just don't import the alternative rootvg. If you will do it it will not be bootable anymore because AIX will rename LVs.
    So just be careful, active AIX will see the second disk as an empty one.
    It doesn't matter which load source have you used: DVD, USB, Network.


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    Dmitry Mironov
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  • 5.  RE: AIX dual boot

    Posted Wed January 20, 2021 09:06 AM
    It is very possible using alternative boot disk. It means that you will have rootvg and alt_rootvg in the systems which has to be labelled as AIX7.1 and AIX7.2 depending on the active OS disks.

    The challenge here is that getting to either of the OS version, the system has to be rebooted by changing some boot disk list which must follow some steps..

    bosboot -ad /dev/diskn
    bootlist -m normal /dev/diskn

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    Olawole Adetayo
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  • 6.  RE: AIX dual boot

    Posted Wed January 20, 2021 01:34 PM
    Q: altinst_rootvg and old_rootvg: Will you see them?
    A: it depends on how you've installed the second OS instance.

    Example
    AIX 7.1 on hdisk1
    Empty hdisk2

    Situation 1:

    You make a clone (smit or alt_disk_clone) to hdisk2.
    -You wil see this clone as altinst_rootvg
    You reboot from this disk (bootlist -m normal hdisk2; reboot)
    -You see hdisk2 as rootvg and hdisk1 as old_rootvg
    ((If you again reboot from hdisk1 than you again will see hdisk1 as rootvg and hdisk2 as altinst_rootvg and so on)).
    OK, you need AIX 7.2
    So, you boot from USB/DVD and update AIX on hdisk2 to AIX 7.2
    What VGs will you see after the upgrade?
    The same: altinst_rootvg or old_rootvg, depends on which disk is active rootvg now.

    Situation 2:

    You boot from USB/DVS and make a New Install AIX 7.2 on hdisk2.
    No any clones before!
    In such case you will see the second disk as empty. Because the current AIX doen't know anything about the content at the second disk. Really all data will stay there, don't try to importvg (!) Just change the bootlist, reboot and you will see it.

    It's because the info about VG stays not only on the disks, but also in the AIX ODM.


    ----
    Now it's my turn:
    What if, in the same example, you:
    1. make a clone to hdisk2.
    2. boot from external media.
    3. Install New AIX 7.2 to hdisk2.
    Which VG will you see when you will boot from hdisk1 or hdisk2?
    I know the answer. Do you?
    If not - THINK!
    Want to learn more - ask.

    With best regards



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    Dmitry Mironov


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  • 7.  RE: AIX dual boot

    Posted Thu January 21, 2021 03:07 AM

    The initial question was "In 1 disk he install AIX 7.1 and in other disk he install AIX 7.2. Now he will boot AIX 7.1 sometime and AIX 7.2 in some other time."

    and "Would they be able to install AIX from a USB drive and avoid the need for the DVD drive in the configuration ?".

    So, no need for alt_rootvg. Simply select the correct adapter and boot device in the SMS menu. And installation of AIX from USB runs on the same way, see

    Using and taking advantage from USB devices and AIX. Just download the AIX flash image from IBM, put it on the stick by "dd", assign the USB adapter to the LPAR and select the USB adapter in the SMS menu (SMS=system management services).

    The SMS menu appears after starting the LPAR in the console of the LPAR by pressing the 1 key as the LPAR boot logo comes up:
    IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM
    IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM IBM

    1 = SMS Menu 5 = Default Boot List

    Press the 1 key multiple times when you see the above line, else the boot continues !


    As we use HMCs, I don't know how to access the AIX console with ASMI, but there is an IBM description of this:
    https://www.ibm.com/support/knowledgecenter/POWER6/iphb6/startsms_asmi.htm
    saying:

    If you have are not using an HMC to start the system management services, complete one of the following tasks:

    • If the ASMI is available on a network-attached console and the system is in standby state, complete the following steps:
      1. On the ASMI Welcome window, specify the ADMIN user ID and password, and click Log In.
      2. In the navigation area, expand Power/Restart Control and select Power On/Off System.
      3. Click Save settings and continue system server firmware boot.
      4. Look for the POST indicators memory, keyboard, network, scsi, speaker, which display across the bottom of the firmware console. For details, see Power-on self-test keys.
      5. Press the numeric 1 key after the word keyboard is displayed and before the word speaker is displayed.
    • If the ASMI is not available and the system is in standby, complete the following steps:
      1. Press the power button on the control panel.
      2. Look for the POST indicators memory, keyboard, network, scsi, speaker, which display across the bottom of the firmware console. For details, see Power-on self-test keys.
      3. Press the numeric 1 key after the word keyboard is displayed and before the word speaker is displayed.
    • If the ASMI is not available and the system has already booted the AIX operating system, complete the following steps:
      1. Reboot the operating system.
      2. Look for the POST indicators memory, keyboard, network, scsi, speaker, which display across the bottom of the firmware console. For details, see Power-on self-test keys.
      3. Press the numeric 1 key after the word keyboard is displayed and before the word speaker is displayed.


    BTW: an inactive rootvg that's not made by alt_rootvg install can be accessed (as every other inactive VG) by importvg. The only point is not to access a filesystem while its active otherwise. That's what a maintenance boot does too.



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    Achim Haag
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  • 8.  RE: AIX dual boot

    Posted Thu January 21, 2021 04:43 AM
    Achim,

    --
    BTW: an inactive rootvg that's not made by alt_rootvg install can be accessed (as every other inactive
    --

    Don't do it, or this rootvg will be not bootable anymore, because there are the same LV names: hd4, hd9var etc. They will be automatically renamed on this VG during the importvg process.

    You may try to see it if perform a small experiment:
    1. create a VG and LV named testlv on it.
    2. exportvg
    3. create the LV named testlv on your rootvg or any other existing VG.
    4. importvg 
    5. Check the LV name.

    The LV name will be changed directly at the LVCB and VGDA (special zones describing the VG structure that resides at the disks).

    PS sorry for typos. Writing from smartphone.



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    Dmitry Mironov
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  • 9.  RE: AIX dual boot

    Posted Thu January 21, 2021 04:59 AM

    Yes, I was wrong, sorry.

    So the only way to access a non-alt_rootvg seems the maintenance boot by network, DVD or USB (with an AIX level even or higher as the accessed rootvg).



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    Achim Haag
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  • 10.  RE: AIX dual boot

    Posted Sun January 24, 2021 12:49 PM

    Achim,
    >So the only way to access a non-alt_rootvg seems the maintenance boot by network, DVD or USB (with an AIX level even or higher as the accessed rootvg).
    Or.. boot from this disk in normal mode. It's really the rootvg, it's bootable, I don't see any problems with it.


    Don't think about the VG name. It's just a label in the ODM. Do you know that:
    -there is the information about the filesystem name in the LV structure (LVCB) on the disk;
    -there is the information about the LV name in the VG structure (VGDA) on the disk;
    -but there is NO information about the VG name on this disk, i.e. VG don't know it's own name!

    What happens when AIX boots? In simple words, firmware load the kernel from the specified disk sector; then the kernel "decides":
    "OK, I am an AIX kernel, I've just booted from some hdisk. So there should be VG on this disk; the VG name should be ROOTVG, because it's a rule"
    and reads the rest VG-realted information from the VGDA.

    To AIX experts: I've described the part of AIX boot progress in simple terms; I know that I've missed a lot.



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    Dmitry Mironov
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