Disk Management

This article focusses on non-LVM and non-MDADM storage. For LVM, NTFS, Samba, MDADM and LUKS volumes there are separate entries.

Universally Unique identifier

Universally Unique identifier (UUID) are identifiers for informations on computer systems. Most notably they are used to identify file systems. This way the UUID of a file system can be used to identify and mount it persistently and correctly.

By listing the directory /dev/disk/by-partuuid all mappings of devices to a UUID are displayed.

Mounting

Mounting a file system makes the files of it accessible to the user. The command mount is used to manually and temporarily mount file systems. Automatic mounting is done by changing the file /etc/fstab.

The exact guide on how to mount specific file systems can be found in their respecitive wiki entries. The following describes the general basics of mounting temporarily and persistently.

The basic mount command for temporarily accessing a file system is the following: mount <path to partition> <path to mount point> All partitions can be found at /dev and the standard mount point is /mnt and its subfolders.

For automatic mounting the following line has to be adapted and added to the file /etc/fstab <specified partition> <path to mount point> <file system> <additional options> <dump flag> <fsck order> The partition can be specified by UUID. The file system varies and a file system specific guide on how to mount them can be found in their respective entries. The dump flag signals if the file system should be dumped. The fsck order signals if a file system should be checked at boot. Boot partitions should be flagged with a 1 for this reason, otherwise 0.

Create Partition

In the following it is assumed that the disk is /dev/sda

open up parted with parted /dev/sdd
if not already done create a partition table with mklabel GPT
create a primary partition (ext4 format) with mkpart primary 2048s 100%
quit parted

<path to partition> points to the partition that will be enlarged (for example /dev/sda2).

Grow non-LVM partition

ATTENTION: Please note that the partition to enlarge has to be the last one with the free space after it.

In the following it is assumed that the partition to enlarge is /dev/sda2

change the size of the partition with parted /dev/sda
inside of parted run print free and check where the free space after your partition ends
run resizepart and follow the instructions; End is the number you checked in the last step (alternatively you can insert 100% as end, if you want to add all the available free space to the partition)
quit parted

Afterwards the file system need to be resized as described in a later section.

Growing a File System

A file system can easily be resized if free space is available on the partition it is stored in. The free space has to be placed behind the partition. This can be done by running the following command:

sudo resize2fs <path to partition>

Shrinking a File System

To shrink a file system the resize2fs command will be used aswell as e2fsck. First the file system needs to be checked for size aswell as data distribution. This can be done using the command sudo e2fsck -f <path to partition>. <path to partition> directs to the volume whose file system should be shrinked - for example /dev/sda1. It has to be the same for the next step aswell. Afterwards the file system can be shrinked with the command sudo resize2fs <path to partition> <new size of the file system>. <new size of the file system> is the size that the file system will be shrunken to in the usual notation (for example 12G). Especially for large file systems this might take a while.

Error solving

This section addresses various problems that can occur and are related to disk-management.

sudo: unable to open ... Read-only file system

Ususally the filesystem will go into read-only mode whe the system is running and there is a consistency error. To fix it run:

sudo fsck -Af -M - check all filesystems If fsck gets stuck after its version banner: fsck from util-linux 2.20.1 you may want to try using the ext4-specific fsck:
fsck.ext4 -f /dev/sda1

cannot access: Transport endpoint is not connected

This error message can occur if a mounted directory is left mounted due to a crash of the filesystem but not accessible anymore. This error can be fixed and the directory made accessible again by running the following command.

fusermount -u <path to mount dir>

If this does not work the following command can be used to unmount the device.

umount -l <path to mount dir>

This section is based on a reply by Jonathan Brown on Stack Overflow.

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