Saturday, December 17, 2016

Expanding a Linux Partition_AWS



Expanding a Linux Partition
Some Amazon EC2 root volumes and volumes that are restored from snapshots contain a partition that actually holds the file system and the data. If you think of a volume as a container, a partition is another container inside the volume, and the data resides on the partition. Growing the volume size does not grow the partition; to take advantage of a larger volume, the partition must be expanded to the new size.
Note
Not all volumes restored from snapshots are partitioned, and this procedure may not apply to your volume. You may just need to resize the file system on your volume to make all of the space available. If you are not sure if your volume has a partition that needs resizing, see To check if your volume partition needs resizing for more information.
If the partition you want to expand is not the root partition, then you can simply unmount it and resize the partition from the instance itself. If the partition you need to resize is the root partition for an instance, the process becomes more complicated because you cannot unmount the root partition of a running instance. You have to perform the following procedures on another instance, which is referred to as a secondary instance.
Important
The following procedures were written for and tested on Amazon Linux. Other distributions with different tool sets and tool versions may behave differently.
Topics
Preparing a Linux Root Partition for Expansion
There are several steps that you need to take to expand the root partition of an instance. If the partition you need to expand is not the root partition, then this procedure is not necessary.
To prepare a Linux root partition for expansion
  1. If your primary instance is running, stop it. You cannot perform the rest of this procedure on a running instance. For more information, see Stop and Start Your Instance.
  2. Check the integrity of your volume. File-system corruption that is picked up by the snapshot may render a restored root volume unbootable.
  3. Take a snapshot of your volume. It can be easy to corrupt or lose your data in the following procedures. If you have a fresh snapshot, you can always start over in case of a mistake and your data will still be safe. For more information, see Creating an Amazon EBS Snapshot.
  4. Record the device name that the volume is attached to. You can find this information on the Root device field of the instance's details pane. The value is likely /dev/sda1or /dev/xvda.
  5. Detach the volume from the primary instance. For more information, see Detaching an Amazon EBS Volume from an Instance.
  6. Attach the volume to another (secondary) instance in the same Availability Zone. For more information, see Attaching an Amazon EBS Volume to an Instance. If your EBS volume is encrypted, you must use a secondary instance that supports Amazon EBS encryption; otherwise, you can use a t2.micro instance for this procedure. For more information, see Supported Instance Types. If you do not already have a secondary instance, you will need to launch one. For more information, see Launching an Instance.
Important
The secondary instance must be running when you attach the volume, and you should not reboot the secondary instance while multiple root volumes are attached; booting an instance with multiple root volumes attached could cause the instance to boot to the wrong volume.
  1. Log in to the secondary instance with SSH. For more information, see Connect to Your Linux Instance. Continue with the next procedure.
Expanding a Linux Partition Using parted
The parted utility is a partition editing tool that is available on most Linux distributions. It can create and edit both MBR partition tables and GPT partition tables. Some versions ofparted (newer than version 2.1) have limited support for GPT partition tables and they may cause boot issues if their version of parted is used to modify boot volumes. You can check your version of parted with the parted --version command.
If you are expanding a partition that resides on a GPT partitioned device, you should choose to use the gdisk utility instead. If you're not sure which disk label type your volume uses, you can check it with the sudo fdisk -l command. For more information, see To expand a Linux partition using gdisk.
To expand a Linux partition using parted
If the partition you need to expand is the root partition, be sure to follow the steps in To prepare a Linux root partition for expansion first.
  1. Identify the device that contains the partition that you want to expand. Use the lsblkcommand to list all devices and partitions attached to the instance.
[ec2-user ~]$ lsblk
NAME    MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
xvdf    202:80   0  100G  0 disk
└─xvdf1 202:81   0    8G  0 part /mnt
xvda1   202:1    0   30G  0 disk /
In this example, the xvdf device has 100 GiB of available storage and it contains an 8 GiB partition.
  1. Unmount the partition if it is mounted. Run the umount command with the value ofMOUNTPOINT from the lsblk command. In this example, the MOUNTPOINT value for the partition is /mnt.
[ec2-user ~]$ sudo umount /mnt
  1. Take a snapshot of your volume (unless you just took one in the previous procedure). It can be easy to corrupt or lose your data in the following procedures. If you have a fresh snapshot, you can always start over in case of a mistake and your data will still be safe. For more information, see Creating an Amazon EBS Snapshot.
  2. Run the parted command on the device (and not the partition on the device). Remember to add the /dev/ prefix to the name that lsblk outputs.
[ec2-user ~]$ sudo parted /dev/xvdf
GNU Parted 2.1
Using /dev/xvdf
Welcome to GNU Parted! Type 'help' to view a list of commands.
  1. Change the parted units of measure to sectors.
(parted) unit s
  1. Run the print command to list the partitions on the device. For certain partition table types, you might be prompted to repair the partition table for the larger volume size. Answer 'Ignore' to any questions about fixing the existing partition table; you will create a new table later.
(parted) print
    1. If you receive the following message, enter 'Ignore' to prevent the backup GPT location from changing.
b.  Error: The backup GPT table is not at the end of the disk, as it should be.  This might mean that another operating
c.  system believes the disk is smaller.  Fix, by moving the backup to the end (and removing the old backup)?
Fix/Ignore/Cancel? Ignore
    1. If you receive the following message, enter 'Ignore' again to keep the space on the drive the same.
e.  Warning: Not all of the space available to /dev/xvdf appears to be used, you can fix the GPT to use all of the
f.  space (an extra 46137344 blocks) or continue with the current setting?
Fix/Ignore? Ignore
  1. Examine the output for the total size of the disk, the partition table type, the number of the partition, the start point of the partition, and any flags, such as boot. For gptpartition tables, note the name of the partition; for msdos partition tables, note theType field (primary or extended). These values are used in the upcoming steps.
The following is a gpt partition table example.
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdf: 209715200s
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start  End        Size       File system  Name                 Flags
128     2048s  4095s      2048s                   BIOS Boot Partition  bios_grub
 1      4096s  16777182s  16773087s  ext4         Linux
The following is an msdos partition table example.
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdg: 104857600s
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start  End        Size       Type     File system  Flags
 1      2048s  35649535s  35647488s  primary  ext3
  1. Delete the partition entry for the partition using the number (1) from the previous step.
(parted) rm 1
  1. Create a new partition that extends to the end of the volume.
(For the gpt partition table example) Note the start point and name of partition 1 above. For the gpt example, there is a start point of 4096s, and the name Linux. Run the mkpart command with the start point of partition 1, the name, and 100% to use all of the available space.
(parted) mkpart Linux 4096s 100%
(For the msdos partition table example) Note the start point and the partition type of partition 1 above. For the msdos example, there is a start point of 2048s and a partition type of primary. Run the mkpart command with a primary partition type, the start point of partition 1, and 100% to use all of the available space.
(parted) mkpart primary 2048s 100%
  1. Run the print command again to verify your partition.
(For the gpt partition table example)
(parted) print
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdf: 209715200s
Sector size (logical/physical): 512B/512B
Partition Table: gpt

Number  Start  End         Size        File system  Name                 Flags
128     2048s  4095s       2048s                    BIOS Boot Partition  bios_grub
 1      4096s  209713151s  209709056s  ext4         Linux
(For the msdos partition table example)
(parted) print
Model: Xen Virtual Block Device (xvd)
Disk /dev/xvdg: 104857600s
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number  Start  End         Size        Type     File system  Flags
 1      2048s  104857599s  104855552s  primary  ext3
  1. Check to see that any flags that were present earlier are still present for the partition that you expanded. In some cases the boot flag may be lost. If a flag was dropped from the partition when it was expanded, add the flag with the following command, substituting your partition number and the flag name. For example, the following command adds the boot flag to partition 1.
(parted) set 1 boot on
You can run the print command again to verify your change.
  1. Run the quit command to exit parted.
(parted) quit
Note
Because you removed a partition and added a partition, parted may warn that you may need to update /etc/fstab. This is only required if the partition number changes.
  1. Check the file system to make sure there are no errors (this is required before you may extend the file system). Note the file system type from the previous print commands. Choose one of the commands below based on your file system type; if you are using a different file system, consult the documentation for that file system to determine the correct check command.
(For ext3 or ext4 file systems)
[ec2-user ~]$ sudo e2fsck -f /dev/xvdf1
e2fsck 1.42.3 (14-May-2012)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/: 31568/524288 files (0.4% non-contiguous), 266685/2096635 blocks
(For xfs file systems)
[ec2-user ~]$ sudo xfs_repair /dev/xvdf1
Phase 1 - find and verify superblock...
Phase 2 - using internal log
        - zero log...
        - scan filesystem freespace and inode maps...
        - found root inode chunk
Phase 3 - for each AG...
        - scan and clear agi unlinked lists...
        - process known inodes and perform inode discovery...
        - agno = 0
        - agno = 1
        - agno = 2
        - agno = 3
        - process newly discovered inodes...
Phase 4 - check for duplicate blocks...
        - setting up duplicate extent list...
        - check for inodes claiming duplicate blocks...
        - agno = 0
        - agno = 1
        - agno = 2
        - agno = 3
Phase 5 - rebuild AG headers and trees...
        - reset superblock...
Phase 6 - check inode connectivity...
        - resetting contents of realtime bitmap and summary inodes
        - traversing filesystem ...
        - traversal finished ...
        - moving disconnected inodes to lost+found ...
Phase 7 - verify and correct link counts...
done
  1. The next steps differ depending on whether the expanded partition belongs on the current instance or if it is the root partition for another instance.
·         If this partition belongs on the current instance, remount the partition at theMOUNTPOINT identified in Step 2.
[ec2-user ~]$ sudo mount /dev/xvdf1 /mnt
After you have mounted the partition, extend the file system to use the newly available space by following the procedures in Extending a Linux File System.
·         If this volume is the root partition for another instance, proceed to the procedures in Returning an Expanded Partition to its Original Instance.
Expanding a Linux Partition Using gdisk
The gdisk utility (sometimes called GPT fdisk) is a text-based, menu-driven tool for creating and editing partition tables, and it has better support for GPT partition tables than parted in some distributions. Many common Linux distributions (such as Amazon Linux and Ubuntu) provide gdisk by default. If your distribution does not provide the gdisk command, you can find out how to get it by visiting Obtaining GPT fdisk; in many cases, it is much easier to launch an Amazon Linux instance to use as a secondary instance because the gdiskcommand is already available.
To expand a Linux partition using gdisk
If the partition you need to expand is the root partition, be sure to follow the steps in To prepare a Linux root partition for expansion first.
  1. Identify the device that contains the partition that you want to expand. Use the lsblkcommand to list all devices and partitions attached to the instance.
[ec2-user ~]$ lsblk
NAME    MAJ:MIN RM  SIZE RO MOUNTPOINT
xvdf    202:80   0  100G  0
└─xvdf1 202:81   0  9.9G  0 /mnt
xvda1   202:1    0   30G  0 /
In this example, the xvdf device has 100 GiB of available storage and it contains an 9.9 GiB partition.
  1. Unmount the partition if it is mounted. Run the umount command with the value ofMOUNTPOINT from the lsblk command. In this example, the MOUNTPOINT value for the partition is /mnt.
[ec2-user ~]$ sudo umount /mnt
  1. Take a snapshot of your volume (unless you just took one in the previous procedure). It can be easy to corrupt or lose your data in the following procedures. If you have a fresh snapshot, you can always start over in case of a mistake and your data will still be safe. For more information, see Creating an Amazon EBS Snapshot.
  2. Run the gdisk command on the device (and not the partition on the device). Remember to add the /dev/ prefix to the name that lsblk outputs.
[ec2-user ~]$ sudo gdisk /dev/xvdf
gdisk /dev/xvdf
GPT fdisk (gdisk) version 0.8.10

Partition table scan:
MBR: protective
BSD: not present
APM: not present
 GPT: present

Found valid GPT with protective MBR; using GPT.
  1. Run the p command to print the partition table for the device.
  2. Examine the output for the disk identifier, partition number, starting sector, code for the partition, and name of the partition. If your volume has multiple partitions, take note of each one.
Command (? for help): p
Disk /dev/xvdf: 209715200 sectors, 100.0 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 947F4655-F3BF-4A1F-8203-A7B30C2A4425
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 20705246
Partitions will be aligned on 2048-sector boundaries
Total free space is 2108 sectors (1.0 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048        20705152   9.9 GiB     EF00  lxroot
In the above example the disk identifier is 947F4655-F3BF-4A1F-8203-A7B30C2A4425, the partition number is 1, the starting sector is 2048, the code is EF00, and the name is lxroot.
  1. Because the existing partition table was originally created for a smaller volume, you need to create a new partition table for the larger volume. Run the o command to create a new, empty partition table.
Command (? for help): o
This option deletes all partitions and creates a new protective MBR.
Proceed? (Y/N): Y
  1. Use the n command to create a new partition entry for each partition on the device.
    • If your volume has only one partition, at each prompt, enter the values that you recorded earlier. For the last sector value, use the default value to expand to the entire volume size.
o    Command (? for help): n
o    Partition number (1-128, default 1): 1
o    First sector (34-209715166, default = 2048) or {+-}size{KMGTP}: 2048
o    Last sector (2048-209715166, default = 209715166) or {+-}size{KMGTP}: 209715166
o    Current type is 'Linux filesystem'
o    Hex code or GUID (L to show codes, Enter = 8300): EF00
Changed type of partition to 'EFI System'
    • If your volume has more than one partition, there is likely a BIOS boot partition, and a main data partition. Create a new partition entry for the BIOS boot partition using the values that you recorded earlier. Create another new partition entry for the main data partition using the values that you recorded earlier, but for the last sector value, use the default value to expand to the entire volume size.
o    Command (? for help): n
o    Partition number (1-128, default 1): 1
o    First sector (34-209715166, default = 2048) or {+-}size{KMGTP}:  2048
o    Last sector (2048-209715166, default = 209715166) or {+-}size{KMGTP}: 4095
o    Current type is 'Linux filesystem'
o    Hex code or GUID (L to show codes, Enter = 8300): EF02
o    Changed type of partition to 'BIOS boot partition'
o     
o    Command (? for help): n
o    Partition number (2-128, default 2): 2
o    First sector (34-209715166, default = 4096) or {+-}size{KMGTP}: 4096
o    Last sector (4096-209715166, default = 209715166) or {+-}size{KMGTP}: 209715166
o    Current type is 'Linux filesystem'
o    Hex code or GUID (L to show codes, Enter = 8300): 0700
Changed type of partition to 'Microsoft basic data'
  1. Use the c command to change the name of each partition to the name of the previous partition. If your partition did not have a name, simply type Enter.
Command (? for help): c
Using 1
Enter name: lxroot
  1. Use the x command to enter the expert command menu.
  2. Use the g command to change the disk identifier to the original value.
Expert command (? for help): g
Enter the disk's unique GUID ('R' to randomize): 947F4655-F3BF-4A1F-8203-A7B30C2A4425
The new disk GUID is 947F4655-F3BF-4A1F-8203-A7B30C2A4425
  1. Use the w command to write the changes to the device and exit.
Expert command (? for help): w

Final checks complete. About to write GPT data. THIS WILL OVERWRITE EXISTING
PARTITIONS!!
Do you want to proceed? (Y/N): Y
OK; writing new GUID partition table (GPT) to /dev/xvdf.
The operation has completed successfully.
  1. Check the file system to make sure there are no errors (this is required before you may extend the file system).
a.    Find the file system type with the following command, substituting the partition you just expanded (this may be /dev/xvdf2 if your volume had multiple partitions).
[ec2-user ~]$ sudo file -sL /dev/xvdf1
b.    Choose one of the commands below based on your file system type; if you are using a different file system, consult the documentation for that file system to determine the correct check command.
(For ext3 or ext4 file systems)
[ec2-user ~]$ sudo e2fsck -f /dev/xvdf1
e2fsck 1.42.3 (14-May-2012)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information
/: 31568/524288 files (0.4% non-contiguous), 266685/2096635 blocks
(For xfs file systems)
Note
You may need to install the xfsprogs package to work with XFS file systems. Use the following command to add XFS support to your Amazon Linux instance.
[ec2-user ~]$ sudo yum install -y xfsprogs
[ec2-user ~]$ sudo xfs_repair /dev/xvdf1
Phase 1 - find and verify superblock...
Phase 2 - using internal log
        - zero log...
        - scan filesystem freespace and inode maps...
        - found root inode chunk
Phase 3 - for each AG...
        - scan and clear agi unlinked lists...
        - process known inodes and perform inode discovery...
        - agno = 0
        - agno = 1
        - agno = 2
        - agno = 3
        - process newly discovered inodes...
Phase 4 - check for duplicate blocks...
        - setting up duplicate extent list...
        - check for inodes claiming duplicate blocks...
        - agno = 0
        - agno = 1
        - agno = 2
        - agno = 3
Phase 5 - rebuild AG headers and trees...
        - reset superblock...
Phase 6 - check inode connectivity...
        - resetting contents of realtime bitmap and summary inodes
        - traversing filesystem ...
        - traversal finished ...
        - moving disconnected inodes to lost+found ...
Phase 7 - verify and correct link counts...
done
                The next steps differ depending on whether the expanded partition belongs on the current instance or if it is the root partition for another instance.
·         If this partition belongs on the current instance, remount the partition at theMOUNTPOINT identified in Step 2.
[ec2-user ~]$ sudo mount /dev/xvdf1 /mnt
After you have mounted the partition, extend the file system to use the newly available space by following the procedures in Extending a Linux File System.
·         If this volume is the root partition for another instance, proceed to the procedures in Returning an Expanded Partition to its Original Instance.
Returning an Expanded Partition to its Original Instance
If you expanded a root partition from another instance, follow this procedure to return the volume to its original instance.
To return an expanded root partition to its original instance
  1. Detach the expanded partition from its secondary instance. For more information, seeDetaching an Amazon EBS Volume from an Instance.
  2. Reattach the volume to the primary instance using the device name that you identified in Step 4 of the preparation procedure. For more information, see Attaching an Amazon EBS Volume to an Instance.
  3. Start the primary instance. For more information, see Stop and Start Your Instance.
  4. (Optional) If you launched a secondary instance for the sole purpose of expanding the partition, you can terminate the instance to stop incurring charges. For more information, see Terminate Your Instance.
  5. Connect to your primary instance and extend the file system to use the newly available space by following the procedures in Extending a Linux File System.
After you are finished with this expanding the file system, you can create an AMI from the instance that you can use to launch new instances with the desired partition size. For more information, see Amazon Machine Images (AMI).

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