Difference between revisions of "Hard Disk Partitioning"
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{{Level|Advanced}} | {{Level|Advanced}} | ||
| + | {{Warning box|Get it right or you will lose data. '''Take a backup!''' Keep in mind if you make a mistake you can loose a whole hard disk. A common error is to switch /dev/sda with /dev/sdb.}} | ||
| − | + | SME Servers Raid Options are largely automated, if you built your system with a single hard disk simply logon as ''admin'' and select ''Disk Redundancy'' to add a new drive to your RAID1 array. The same procedure is used if you have a disk failure in a RAID array and you have replaced that failed disk. | |
| − | + | But with the best laid plans things don't always go according to plan, these are the processes required to do it manually. | |
| − | + | See also: [[Raid:Manual Rebuild]] | |
| − | === | + | === Is the Disk Partitioned Correctly ? === |
Here two disks are partitioned identically | Here two disks are partitioned identically | ||
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===== message Log showing Grub errors during the processus of installation===== | ===== message Log showing Grub errors during the processus of installation===== | ||
| − | If we try to install | + | If we try to install grub you will see these errors messages |
add_drive_to_raid: Waiting for boot partition to sync before installing grub... | add_drive_to_raid: Waiting for boot partition to sync before installing grub... | ||
| Line 82: | Line 83: | ||
== HowTo: Partition / Re-Partition a disk == | == HowTo: Partition / Re-Partition a disk == | ||
| − | {{note box|if you | + | {{note box|if you are using the disk for the first time you can go straight to the next section otherwise you need to erase the old partitions before you create a new one. We will presume you have two existing partitions as is the default partitioning on a SME Server raid1.}} |
=== Delete Existing Partitions === | === Delete Existing Partitions === | ||
| Line 120: | Line 121: | ||
=== Create new partitions === | === Create new partitions === | ||
| − | {{note box|Now we will create two partitions for md1 and md2, as it is the default partitioning of SME. You can make another choice to create just one partition if you want a data disk in a raid array. At this point you will | + | {{note box|Now we will create two partitions for md1 and md2, as it is the default partitioning schema of SME. You can make another choice to create just one partition if you want a data disk in a raid array. At this point you will allocate the whole disk to partition 1. In this case there is no need to give a boot flag (see below the flag "a")}} |
{{warning box|Note: change the partitions system id to reflect Linux raid autodetect}} | {{warning box|Note: change the partitions system id to reflect Linux raid autodetect}} | ||
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== HowTo: Write the GRUB boot sector == | == HowTo: Write the GRUB boot sector == | ||
| − | {{note box|The | + | {{note box|The new disk requires grub to ensure the boot sequence}} |
| + | |||
| + | {{Warning box|as the dd command is named "data destroyer" you need to be extremely prudent and sure of the name of source partition and/or destination. At first you should skip the dd command, Step 1 below, and attempt to install grub without it, see Step 2 below. If grub can be installed without using dd, then Step 1 can be discarded. }} | ||
[root@ ~]# '''dd if=/dev/sda1 of=/dev/sdb1''' | [root@ ~]# '''dd if=/dev/sda1 of=/dev/sdb1''' | ||
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completions of a device/filename.] | completions of a device/filename.] | ||
| − | grub> '''device ( | + | grub> '''device (hd1) /dev/sdb''' |
| − | grub> '''root ( | + | grub> '''root (hd1,0)''' |
Filesystem type is ext2fs, partition type 0xfd | Filesystem type is ext2fs, partition type 0xfd | ||
| − | grub> '''setup ( | + | grub> '''setup (hd1)''' |
Checking if "/boot/grub/stage1" exists... no | Checking if "/boot/grub/stage1" exists... no | ||
Checking if "/grub/stage1" exists... yes | Checking if "/grub/stage1" exists... yes | ||
Checking if "/grub/stage2" exists... yes | Checking if "/grub/stage2" exists... yes | ||
Checking if "/grub/e2fs_stage1_5" exists... yes | Checking if "/grub/e2fs_stage1_5" exists... yes | ||
| − | Running "embed /grub/e2fs_stage1_5 ( | + | Running "embed /grub/e2fs_stage1_5 (hd1)"... 16 sectors are embedded. |
succeeded | succeeded | ||
| − | Running "install /grub/stage1 ( | + | Running "install /grub/stage1 (hd1) (hd1)1+16 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded |
Done. | Done. | ||
Latest revision as of 16:30, 20 February 2013
SME Servers Raid Options are largely automated, if you built your system with a single hard disk simply logon as admin and select Disk Redundancy to add a new drive to your RAID1 array. The same procedure is used if you have a disk failure in a RAID array and you have replaced that failed disk.
But with the best laid plans things don't always go according to plan, these are the processes required to do it manually.
See also: Raid:Manual Rebuild
Is the Disk Partitioned Correctly ?
Here two disks are partitioned identically
[root@ ~]# fdisk -lu /dev/sda; fdisk -lu /dev/sdb Disk /dev/sda: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Device Boot Start End Blocks Id System /dev/sda1 * 63 208844 104391 fd Linux raid autodetect /dev/sda2 208845 1953520064 976655610 fd Linux raid autodetect Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 63 208844 104391 fd Linux raid autodetect /dev/sdb2 208845 1953520064 976655610 fd Linux raid autodetect
Example : Incorrecty Partitioned 2nd Disk
In this example the partitions are set too close to the start of the disk and there is no room for GRUB to be written, the disk will not boot, there will not be enough room for grub staging
[root@ ~]# fdisk -lu /dev/sdb; fdisk -lu /dev/sdb Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 13 104384+ fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 13 121601 976655647 fd Linux raid autodetect Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors Units = sectors of 1 * 512 = 512 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 208769 104384+ fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 208770 1953520063 976655647 fd Linux raid autodetect
message Log showing Grub errors during the processus of installation
If we try to install grub you will see these errors messages
add_drive_to_raid: Waiting for boot partition to sync before installing grub... add_drive_to_raid: Probing devices to guess BIOS drives. This may take a long time. add_drive_to_raid: add_drive_to_raid: add_drive_to_raid: GNU GRUB version 0.95 (640K lower / 3072K upper memory) add_drive_to_raid: add_drive_to_raid: [ Minimal BASH-like line editing is supported. For the first word, TAB add_drive_to_raid: lists possible command completions. Anywhere else TAB lists the possible add_drive_to_raid: completions of a device/filename.] add_drive_to_raid: grub> device (hd0) /dev/sdb add_drive_to_raid: grub> root (hd0,0) add_drive_to_raid: Filesystem type is ext2fs, partition type 0xfd add_drive_to_raid: grub> setup (hd0) add_drive_to_raid: Checking if "/boot/grub/stage1" exists... no add_drive_to_raid: Checking if "/grub/stage1" exists... yes add_drive_to_raid: Checking if "/grub/stage2" exists... yes add_drive_to_raid: Checking if "/grub/e2fs_stage1_5" exists... yes add_drive_to_raid: Running "embed /grub/e2fs_stage1_5 (hd0)"... failed (this is not fatal) add_drive_to_raid: Running "embed /grub/e2fs_stage1_5 (hd0,0)"... failed (this is not fatal) add_drive_to_raid: Running "install /grub/stage1 (hd0) /grub/stage2 p /grub/grub.conf "... succeeded add_drive_to_raid: Done. add_drive_to_raid: grub> quit
HowTo: Partition / Re-Partition a disk
Delete Existing Partitions
[root@ ~]# fdisk /dev/sdb The number of cylinders for this disk is set to 121601. There is nothing wrong with that, but this is larger than 1024, and could in certain setups cause problems with: 1) software that runs at boot time (e.g., old versions of LILO) 2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK) Command (m for help): p Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 13 104384+ fd Linux raid autodetect Partition 1 does not end on cylinder boundary. /dev/sdb2 13 121601 976655647 fd Linux raid autodetect Command (m for help): d Partition number (1-4): 1 Command (m for help): d Selected partition 2 Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
Create new partitions
[root@ ~]# fdisk /dev/sdb The number of cylinders for this disk is set to 121601. There is nothing wrong with that, but this is larger than 1024, and could in certain setups cause problems with: 1) software that runs at boot time (e.g., old versions of LILO) 2) booting and partitioning software from other OSs (e.g., DOS FDISK, OS/2 FDISK) Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 1 First cylinder (1-121601, default 1): Using default value 1 Last cylinder or +size or +sizeM or +sizeK (1-121601, default 121601): 13 Command (m for help): n Command action e extended p primary partition (1-4) p Partition number (1-4): 2 First cylinder (14-121601, default 14): Using default value 14 Last cylinder or +size or +sizeM or +sizeK (14-121601, default 121601): Using default value 121601 Command (m for help): a Partition number (1-4): 1 Command (m for help): t Partition number (1-4): 1 Hex code (type L to list codes): fd Changed system type of partition 1 to fd (Linux raid autodetect) Command (m for help): t Partition number (1-4): 2 Hex code (type L to list codes): fd Changed system type of partition 2 to fd (Linux raid autodetect) Command (m for help): p Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes 255 heads, 63 sectors/track, 121601 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sdb1 * 1 13 104391 fd Linux raid autodetect /dev/sdb2 14 121601 976655610 fd Linux raid autodetect Command (m for help): w The partition table has been altered! Calling ioctl() to re-read partition table. Syncing disks.
HowTo: Write the GRUB boot sector
[root@ ~]# dd if=/dev/sda1 of=/dev/sdb1
[root@ ~]# grub
GNU GRUB version 0.95 (640K lower / 3072K upper memory)
[ Minimal BASH-like line editing is supported. For the first word, TAB
lists possible command completions. Anywhere else TAB lists the possible
completions of a device/filename.]
grub> device (hd1) /dev/sdb
grub> root (hd1,0)
Filesystem type is ext2fs, partition type 0xfd
grub> setup (hd1)
Checking if "/boot/grub/stage1" exists... no
Checking if "/grub/stage1" exists... yes
Checking if "/grub/stage2" exists... yes
Checking if "/grub/e2fs_stage1_5" exists... yes
Running "embed /grub/e2fs_stage1_5 (hd1)"... 16 sectors are embedded.
succeeded
Running "install /grub/stage1 (hd1) (hd1)1+16 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
Done.
grub> quit
