Linux – Can you change the partition type on a linux server without starting up fdisk

fdisklinuxsoftware-raid

I'm looking for a way to change a partition type on a linux system without starting fdisk. (In this particular case from "linux" to "softwareRAID")

The ultimate goal here is a script that is going to take /dev/sda and automatically create a software RAID1 with /dev/sdb

I'm not looking for anyone here to write me a script, just trying to provide some info changing the partition type in a script. I can take care of the rest.

Thanks in advance.

Best Answer

or you could use sfdisk, it's also designed to be scriptable.

e.g. to change partition 1 of /dev/sda to type 0xfd (linux raid):

sfdisk --id /dev/sda 1 fd

you can also dump out an existing partition table to a file (in a format that is intended to be re-imported back into sfdisk), then modify that file with vi/awk/sed/perl/ed/whatever and then feed it back in to sfdisk.

e.g.

sfdisk -d /dev/sda | sed -e 's/Id=83/Id=fd/' > /tmp/sda.txt
sfdisk /dev/sda </tmp/sda.txt

i often use that when building raid arrays of identical disks. manually create the partition table on one drive then use sfdisk to copy it to the other drives.

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Linux – Monitor Disk via SNMP polling

You should check the Host Resources MIB. The OID you are mentioning is the hrDeviceDescr field. If you look further in that MIB, you can see the hrDeviceStatus, which is an integer defined as follows:

The current operational state of the device described by this row of the table. A value unknown(1) indicates that the current state of the device is unknown. running(2) indicates that the device is up and running and that no unusual error conditions are known. The warning(3) state indicates that agent has been informed of an unusual error condition by the operational software (e.g., a disk device driver) but that the device is still 'operational'. An example would be a high number of soft errors on a disk. A value of testing(4), indicates that the device is not available for use because it is in the testing state. The state of down(5) is used only when the agent has been informed that the device is not available for any use.

Thus, you should probably better monitor the following OID: .1.3.6.1.2.1.25.3.2.1.5.1552.

Linux – Cannot install grub to RAID1 (md0)

The warning points out the root cause. The new disk that you used for the replacement probably used to have a filesystem on it and grub-setup is now confused by the metadata that is probably still in there.

So, just wipe out everything at the beginning of the disk up to the first partition. I took the 62 number from the fdisk -l output. It says that 63 is the start of the first partition, which sounds like there are 62 sectors before it that you can clean out.

dd if=/dev/zero of=/dev/sda bs=512 count=62

Then recreate the partition table:

sfdisk -d /dev/sdb | sfdisk /dev/sda

sfdisk will probably complain about "the kernel may be using the old partition table" but you can ignore the warning since you are not really changing the partition table.

Then you should be able to grub-install /dev/sda.

Update:

If you are still getting errors, try taking the disk out of the RAID and zeroing out more data from the beginning and the end. Or just zero out the whole disk (dd if=/dev/zero of=/dev/sda). Then add it back to the RAID as you did before, starting from sfdisk -d /dev/sdb | sfdisk /dev/sda. And consider switching to metadata format 1.0 as was recommended in a few other places.

Best Answer

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