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few question

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ani007
Super Advisor

few question

HI All,
I am not good in linux,I know hp-ux only.Could you please ans these que...

Red Hat Enterprise Linux Server release 5.5 (Tikanga)
2.6.18-194.11.1.el5

How to check primary and alternate boot path in RHEL 5
How to check external disk are there or not , please find the fdisk -l o/p as attachment
How to check the Disk striping is enable in data volume if any..
How i will take a backup of VG configuration file
2 REPLIES
Matti_Kurkela
Honored Contributor
Solution

Re: few question

> How to check primary and alternate boot path in RHEL 5

Typically there is no "primary" or "alternate" boot path in PC hardware. (Remember though that PC hardware comes from many manufacturers, and there are no real user interface standards at the PC BIOS level: only some conventions that have become de-facto standards.)

In HP Proliant hardware, you typically choose one disk controller to be the boot controller using the BIOS menu, and maybe one particular disk on that controller to be the boot disk using the controller's own configuration menu (typically accessible by pressing F8 or some other key when prompted at boot time). If the boot disk cannot be chosen in this way, it will be determined using some fixed rule (most likely LUN 0 and/or the lowest SCSI ID).

Once the boot disk has been determined, the system will read the Master Boot Record (MBR) from that disk. It's block #0: the very first block on that disk. With a default installation of RHEL 5, this contains the first stage of a bootloader named GRUB. The code in the MBR will read the rest of GRUB's code, and then GRUB will present a boot menu to the console.

This boot menu is configurable at /boot/grub/grub.conf, and it can hold an indefinite number of boot paths (if the main menu becomes full, you can build sub-menus if you want).

> How to check external disk are there or not , please find the fdisk -l o/p as attachment

In RHEL 5, the /dev directory is managed by the udev subsystem. In practice, that means each device node will appear if and only if the corresponding device exists and is recognized by the kernel.

So yes, all those disks you see are there... although I guess you might be seeing multiple paths to the same FibreChannel LUN.

> How to check the Disk striping is enable in data volume if any..

Striping can be done at multiple levels:
- at the hardware RAID array (check by using the appropriate hardware RAID configuration tool)
- at the software RAID level, if used (check with "cat /proc/mdstat" and/or using the mdadm command)

- at the LVM level (check with "lvs -o +stripes"; if the #Str field has a value other than 1, LVM-level striping is in use)

Anyway, if you're using modern enterprise-grade SAN storage, the LUNs you're seeing are most likely logical constructs that have already been RAIDed, mirrored, striped, cached, and sliced at the storage system level: any further striping at the OS level is not likely to be worth the effort, and may actually be counter-productive if done without understanding the internal workings of the storage system.

>How i will take a backup of VG configuration file

:) Do you see a "VG configuration file" anywhere?

The actual VG configuration is not stored in files at all: all the VG configuration information is embedded in the PV headers.

When the system is booting or you run "vgscan" (which, by the way, is not a scary command at all in Linux), the system will look at the beginning of each disk device and partition that is currently visible. If the disk or partition contains a LVM PV header, the PV automatically becomes "known" to the LVM. If the PV is member of a VG the system has not yet seen, the system becomes aware of the VG too.

There is no need to have the VG directory created ahead of time: when a VG is activated, the vgchange command and udev will work together to create all the necessary device nodes automatically.

NOTE:
Don't make the mistake of assuming that Linux LVM is the same as HP-UX LVM: their user interface may be similar, but their administration procedures are rather different. For example, on Linux you must unlearn everything you learned about exporting VGs on HP-UX: although the commands for "exporting" and "importing" a volume group exist, they work very differently and are not necessary most of the time.

MK
MK
ani007
Super Advisor

Re: few question

tnx