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Hard Disk Partitioning (view source)

Revision as of 17:30, 20 February 2013

9,314 bytes added ,  17:30, 20 February 2013
→‎HowTo: Write the GRUB boot sector
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work in progress you are welcome to disturb me
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{{Level|Advanced}}
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{{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.}}
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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.
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But with the best laid plans things don't always go according to plan, these are the processes required to do it manually.
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See also: [[Raid:Manual Rebuild]]
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=== Is the Disk Partitioned Correctly ? ===
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Here two disks are partitioned identically
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[root@ ~]# '''fdisk -lu /dev/sda; fdisk -lu /dev/sdb'''
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Disk /dev/sda: 1000.2 GB, 1000204886016 bytes
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255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
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Units = sectors of 1 * 512 = 512 bytes
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    Device Boot      Start        End      Blocks  Id  System
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/dev/sda1  *          63      208844      104391  fd  Linux raid autodetect
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/dev/sda2          208845  1953520064  976655610  fd  Linux raid autodetect
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Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
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255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
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Units = sectors of 1 * 512 = 512 bytes
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    Device Boot      Start        End      Blocks  Id  System
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/dev/sdb1  *          63      208844      104391  fd  Linux raid autodetect
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/dev/sdb2          208845  1953520064  976655610  fd  Linux raid autodetect
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==== Example : Incorrecty Partitioned 2nd Disk ====
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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''
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[root@ ~]# '''fdisk -lu /dev/sdb; fdisk -lu /dev/sdb'''
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Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
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255 heads, 63 sectors/track, 121601 cylinders
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Units = cylinders of 16065 * 512 = 8225280 bytes
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    Device Boot      Start        End      Blocks  Id  System
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/dev/sdb1  *          1          13      104384+  fd  Linux raid autodetect
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'''Partition 1 does not end on cylinder boundary.'''
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/dev/sdb2              13      121601  976655647  fd  Linux raid autodetect
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Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
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255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
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Units = sectors of 1 * 512 = 512 bytes
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    Device Boot      Start        End      Blocks  Id  System
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/dev/sdb1  *          1      208769      104384+  fd  Linux raid autodetect
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'''Partition 1 does not end on cylinder boundary.'''
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/dev/sdb2          208770  1953520063  976655647  fd  Linux raid autodetect
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===== message Log showing Grub errors during the processus of installation=====
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If we try to install grub you will see these errors messages
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add_drive_to_raid: Waiting for boot partition to sync before installing grub...
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add_drive_to_raid: Probing devices to guess BIOS drives. This may take a long time.
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add_drive_to_raid:
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add_drive_to_raid:
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add_drive_to_raid:    GNU GRUB  version 0.95  (640K lower / 3072K upper memory)
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add_drive_to_raid:
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add_drive_to_raid:  [ Minimal BASH-like line editing is supported.  For the first word, TAB
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add_drive_to_raid:    lists possible command completions.  Anywhere else TAB lists the possible
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add_drive_to_raid:    completions of a device/filename.]
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add_drive_to_raid: grub> device (hd0) /dev/sdb
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add_drive_to_raid: grub> root (hd0,0)
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add_drive_to_raid:  Filesystem type is ext2fs, partition type 0xfd
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add_drive_to_raid: grub> setup (hd0)
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add_drive_to_raid:  Checking if "/boot/grub/stage1" exists... no
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add_drive_to_raid:  Checking if "/grub/stage1" exists... yes
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add_drive_to_raid:  Checking if "/grub/stage2" exists... yes
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add_drive_to_raid:  Checking if "/grub/e2fs_stage1_5" exists... yes
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add_drive_to_raid:  Running "embed /grub/e2fs_stage1_5 (hd0)"... failed (this is not fatal)
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add_drive_to_raid:  Running "embed /grub/e2fs_stage1_5 (hd0,0)"... failed (this is not fatal)
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add_drive_to_raid:  Running "install /grub/stage1 (hd0) /grub/stage2 p /grub/grub.conf "... succeeded
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add_drive_to_raid: Done.
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add_drive_to_raid: grub> quit
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== HowTo: Partition / Re-Partition a disk ==
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{{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.}}
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=== Delete Existing Partitions ===
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[root@ ~]# '''fdisk /dev/sdb'''
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The number of cylinders for this disk is set to 121601.
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There is nothing wrong with that, but this is larger than 1024,
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and could in certain setups cause problems with:
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1) software that runs at boot time (e.g., old versions of LILO)
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2) booting and partitioning software from other OSs
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    (e.g., DOS FDISK, OS/2 FDISK)
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Command (m for help): '''p'''
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Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
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255 heads, 63 sectors/track, 121601 cylinders
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Units = cylinders of 16065 * 512 = 8225280 bytes
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    Device Boot      Start        End      Blocks  Id  System
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/dev/sdb1  *          1          13      104384+  fd  Linux raid autodetect
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Partition 1 does not end on cylinder boundary.
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/dev/sdb2              13      121601  976655647  fd  Linux raid autodetect
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Command (m for help): '''d'''
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Partition number (1-4): '''1'''
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Command (m for help): '''d'''
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Selected partition 2
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Command (m for help): '''w'''
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The partition table has been altered!
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Calling ioctl() to re-read partition table.
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Syncing disks.
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=== Create new partitions ===
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{{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")}}
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{{warning box|Note: change the partitions system id to reflect Linux raid autodetect}}
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[root@ ~]# fdisk /dev/sdb
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The number of cylinders for this disk is set to 121601.
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There is nothing wrong with that, but this is larger than 1024,
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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)
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Command (m for help): '''n'''
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Command action
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    e  extended
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    p  primary partition (1-4)
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'''p'''
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Partition number (1-4): 1
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First cylinder (1-121601, default 1):
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Using default value 1
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Last cylinder or +size or +sizeM or +sizeK (1-121601, default 121601): 13
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Command (m for help): '''n'''
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Command action
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    e  extended
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    p  primary partition (1-4)
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'''p'''
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Partition number (1-4): 2
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First cylinder (14-121601, default 14):
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Using default value 14
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Last cylinder or +size or +sizeM or +sizeK (14-121601, default 121601):
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Using default value 121601
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Command (m for help): '''a'''
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Partition number (1-4): '''1'''
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Command (m for help): '''t'''
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Partition number (1-4): '''1'''
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Hex code (type L to list codes): '''fd'''
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Changed system type of partition 1 to fd (Linux raid autodetect)
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Command (m for help): '''t'''
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Partition number (1-4): '''2'''
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Hex code (type L to list codes): '''fd'''
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Changed system type of partition 2 to fd (Linux raid autodetect)
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Command (m for help): '''p'''
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Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
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255 heads, 63 sectors/track, 121601 cylinders
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Units = cylinders of 16065 * 512 = 8225280 bytes
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 +
    Device Boot      Start        End      Blocks  Id  System
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/dev/sdb1  *          1          13      104391  fd  Linux raid autodetect
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/dev/sdb2              14      121601  976655610  fd  Linux raid autodetect
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Command (m for help): '''w'''
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The partition table has been altered!
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Calling ioctl() to re-read partition table.
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Syncing disks.
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== HowTo: Write the GRUB boot sector ==
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{{note box|The new disk requires grub to ensure the boot sequence}}
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{{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. }}
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[root@ ~]# '''dd if=/dev/sda1 of=/dev/sdb1'''
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[root@ ~]# '''grub'''
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    GNU GRUB  version 0.95  (640K lower / 3072K upper memory)
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  [ Minimal BASH-like line editing is supported.  For the first word, TAB
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    lists possible command completions.  Anywhere else TAB lists the possible
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    completions of a device/filename.]
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grub> '''device (hd1) /dev/sdb'''
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grub> '''root (hd1,0)'''
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  Filesystem type is ext2fs, partition type 0xfd
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grub> '''setup (hd1)'''
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  Checking if "/boot/grub/stage1" exists... no
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  Checking if "/grub/stage1" exists... yes
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  Checking if "/grub/stage2" exists... yes
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  Checking if "/grub/e2fs_stage1_5" exists... yes
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  Running "embed /grub/e2fs_stage1_5 (hd1)"...  16 sectors are embedded.
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succeeded
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  Running "install /grub/stage1 (hd1) (hd1)1+16 p (hd1,0)/grub/stage2 /grub/grub.conf"... succeeded
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Done.
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grub> '''quit'''
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[[Category:Howto]][[Category:Administration:Storage]]
 
[[Category:Howto]][[Category:Administration:Storage]]
Retrieved from "https://wiki.koozali.org/Special:MobileDiff/18238...18892"

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