Storage

See also: Administrative, Hardware, Virtualization

Partitioning

cfdisk

A command line user interface (CLUI) wrapper for fdisk.

fdisk

Usage

Explanation

-l

lists all partitions, sector and disk label information

m

shows menu options

p

show current partition layout

d

deletes partition

Example

Explanation

/dev/sdc

modify partitions on the third SATA drive

parted

Partition manager that supports creating, reading, updating, and deleting MBR and GPT partitions.

Usage

Explanation

help

show the help guide

help mkpart

shows how to make a new partition

select

select a partition

print all

shows all the partitions; you will need to know where the last one ends to create a new one

mktable

create either a “”msdos”” (MBR) or “”gpt”” partition table on the selected drive

align-check optimal

check a partition to see if it is properly aligned

mkfs.btrfs

Package: btrfs-progs

Create Btrfs file systems.

Usage

Explanation

-d

specify a RAID type (raid0, raid1, raid5, raid6, raid10) and drives for creating a RAID for daa

-m

the same as “”-d”” but instead specifying where the RAID filesystem metadata should be spread out to

btrfs

Manage Btrfs partitions.

Usage

Explanation

filesystem show

list all BTRFS partitions and their usage

filesystem df /

show disk usage on the root partition; this should be used instead of just running “”df”” outside of the btrfs command

filesystem resize {+|-}<SIZE>{m|g}

resize the filesystem on an active/live mount

subvolume list

list all of the snapshots and subvolumes under a specified mount directory

snapshot create

create a snapshot of the partition

subvolume snapshot

create a snapshot of a subvolume

filesystem defragment -r -v -c lzo

defragment the system files, recursively, verbosely, and compress them using the high performance “lzo” algorithm; be sure to add the “compress=lzo” mount option in /etc/fstab for the partition

balance start / -v

rebalance/defragment the repartition at the block level, on the root partition, verbosely; this will help free up space

Example

Explanation

subvolume create /var/ /var/var-snapshot/

create a snapshot of the /var/ folder

mkfs.ext4

Example

Explanation

/dev/sdc3

creates a ext4 formatted partition on /dev/sdc3

mkswap

Package: util-linux

Example

Explanation

/dev/sda2

creates swap partition format on /dev/sda2

swapon

Package: util-linux

Configure Linux to swap on certain partitions.

Example

Explanation

/dev/sda2

tells Linux swap on /dev/sda2

partclone

An efficient partition backup utility.

Usage

Explanation

-c

clone a partition

-r

restore a cloned partition

-s

specify the source partition

-o

save the partition clone to a specified file

mount

Mount a partition onto a folder.

Usage

Explanation

-l

lists all current mounts

-r

read-only

-t

file system to use

-o loop

for loop devices such as ISO images

-o remount

remount a directory

-a

remounts all entries in the /etc/fstab

Example

Explanation

/dev/sda1 /var

mounts the first SCSI drive’s (sda) first partition onto the folder /var

umount

Usage

Explanation

-l

lazy unmount; unmount the file system and let the running processes on it complete

-f

force dismount now

Example

Explanation

/var

dismount the partition that is on /var

lsblk

Lists partition, their size, and mount point information.

Usage

Explanation

–scsi

list SCSI devices like iSCSI, SATA, SAS, etc.

-f

show file systems

Usage

Explanation

/dev/sda

show information only about the sda drive

blkid

Shows UUIDs and labels for all of the partitions.

Usage

Explanation

-c /dev/null

regenerate the partition UUIDs for the /etc/blkid.tab file

touch /forcefsck

Forces a files system check on the next boot.

dd

Usage

Explanation

if=

specify an input device to read from

of=

specify an output device to write to

bs=

specify the byte size

count=

number of times it should copy each byte size

conv=fdatasync

flush data to the disk; do not cache it in memory

Example

Explanation

if=/dev/zero of=/tmp/50MB.img bs=1M count=50

create a blank file that is 50MB

if=/dev/sda1 of=file.img

copy blocks from a partition to a file

df

Show disk space usage.

Usage

Explanation

-h

human readable space usage

-i

inonde/file count

-T

also display the filesystem types

-t

only show filesystems of this type

Example

Explanation

-h -t xfs

show human readable sizes for only XFS file systems

du

Show folder disk space usage.

Usage

Explanation

-h

human readable size format

–max-depth=

the maximum number of subdirectories to find their disk space

Example

Explanation

-h –max-depth=2

show sizes up to two directories deep

ncdu

Interactively show and navigate through “du” disk space usage reports.

testdisk

Data recovery tool.

fsck

File system check utility for helping fixing corrupt file systems.

Usage

Explanation

-y

automatically attempt to repair any problems

-t

the file system type

-C

show the progress

-V

verbosely show the specific file system commands that are being run and their output

Example

Explanation

-C -t ext4 -y /dev/sdb2

automatically fix any problems with the ext4 file system on /dev/sdb2

dumpe2fs

Lookup UUIDs of partitions. These can be used in /etc/fstab.

dmesg

Kernel logs for hardware devices. After plugging in a USB device, check this to find it’s device name and partition to mount.

Example

Explanation

dmesg | grep SCSI

shows all connected SCSI devices

mkisofs

Create ISO images.

Usage

Explanation

-o <FILE>.iso <DIRECTORY>

creates an ISO file from the contents of a directory

lsof

List open files is used to show what processes are using a certain file or directory.

Usage

Explanation

+D <DIRECTORY>

shows what PIDs are using the drive

fuser

Usage

Explanation

-uz <DIRECTORY>

forcefully unmount a a file system

-mv <DIRECTORY>

used to see what user’s are using the file or directory

iostat

Usage

Explanation

-x <INTEGER>

monitor every specified number of seconds

Example

Explanation

-x 5

report on I/O usage every 5 seconds

partprobe

Package: parted

Rescan for the latest information about available partitions. Sometimes required after updating or changing a partition.

smartctl

Package: smartmontools

Monitor drive health using SMART firmware (standard on modern storage devices).

Usage

Explanation

-a

shows all SMART information

-i

shows detailed drive information

-H

shows health status

-t

test for any errors, this can be “short” or “long”

-l selftest

shows the results of a test

-s {on|off}

turn SMART recording on or off for a specified drive

Example

Explanation

-t short /dev/sdb

run a quick test on the drive /dev/sdb

kpartx

Find and attach partitions from storage devices.

Usage

Explanation

-a

find all partitions in a given LV or image file and create loop devices for them

-d

detach the loop devices for a given LV or image file

-u

update the partition mapping

-v

verbose

losetup

Controls loop devices.

Usage

Explanation

-a

view all loop devices created by losetup

-d <LOOP_DEVICE>

detach a loop device

–detach-all

detach all loop devices created by losetup

xfs_admin

Manage XFS partitions.

Usage

Explanation

-L

creates a label

e2label

Create labels on EXT file systems.

Usage

Explanation

<DEVICE>

shows any label names

<DEVICE> <LABLE>

create a label for a device

Example

Explanation

/dev/sda1 BackupDrive

label sda1 as BackupDrive

mdadm

Create and manage software RAIDs.

Usage

Explanation

–create

create a RAID…

–level=<INTEGER>

…specify the RAID level

–raid-device=<INTEGER>

…and specify the amount of drives to be used.

–detail

shows details about a current RAID

–detail –scan

automatically scan for all RAIDs in use and show details

–examine –scan

look for inactive RAIDs

–assemble

recreate RAID with specified drives

–assemble –scan

automatically recreate existing RAIDs

–stop /dev/md<NUMBER>

disable a RAID device

Example

Explanation

mdam –create –level=0 –raid-device=2 /dev/md0 /dev/sda /dev/sdb

use sda and sdb to create a software RAID0

ssm

Create and manage encrypted partitions.

Usage

Explanation

create

create a new volume

open

specify a partition and a mapper to map it to

close

remove the mapper device

–fstype

specify filesystem

–encrypt

specify encryption

cryptsetup

Usage

Explanation

-y

verify password; ask for it to be input twice

luksFormat

specify a partition to format with LUKS encryption

open –type luks /dev/<DEVICE> <MAP>

mount the encrypted partition

close

remove the mapper device

open –type luks /dev/sda4 mydata

mount the /dev/sda4 partition as /dev/mapper/mydata

od

Octal dump is used to read 8 bits (1 byte) at a time of data directly from a storage device.

Usage

Explanation

-c

shows special characters

-N<INTEGER>

read the first specified number of bytes

-j<INTEGER>

skip the first specified number of bytes

-v

output duplicate information

Example

Explanation

-N32

read the first 32 bytes

-j512

skip the first 512 bytes

gddrescue

GNU ddrescue.

Usage

Explanation

-r 1

try to recover bad sectors

-n

copy non-error sectors

ddrescue

Not to be confused with GNU ddrescue.

guestfish

Package: libguestfs-tools-c

Mount QCOW2 images interactively.

Usage

Explanation

–rw

mount in read/write mode

–ro

mount in read-only mode

-a

specify the image file

>run

run a search of information on the used disk

>list-filesystems

show all of the filesystems

>mount

mount a partition onto a mountpoint

>ls

list a directory

>edit

open up the “”vi”” editor

>touch

create a new file

>exit

properly close the image and exit out of the prompt

Example

Explanation

echo -e “runnlist-filesystems” | guestfish -a centos-7.qcow

use guestfish to non-interactively view the file systems on a QCOW2 image

guestmount

Mount QCOW2 images non-interactively.

Usage

Explanation

-a

specify the image file

-m

specify the partition to use and then a mount point

–rw

mount in read-write mode

–ro

mount in read-only mode

Example

Explanation

guestmount -a image.qcow2 -m /dev/sda1 –rw /mnt

mount the sda1 partition from a QCOW2 image in a writable mode to the /mnt directory

guestunmount

Unmount QCOW2 image partitions mounted by guestmount.

LVM

The Logical Volume Manager (LVM) is an implementation to help easily configure and setup partitions and drives.

pvcreate

Create physical volumes.

Example

Explanation

pvcreate /dev/sdb1 /dev/sdc1 /dev/sdc2

create a physical volume from these three partitions

pvremove

Remove physical volumes.

Example

Explanation

/dev/sdb1 /dev/sdc1 /dev/sdc2

remove these three partitions from physical volumes

pvdisplay

Show all physical of the LVM partitions.

vgcreate

Create logical volume groups.

Example

Explanation

fileserver /dev/sdb1 /dev/sdc1

creates a volume group of LVMs that can be partitioned for actual use

vgdisplay

Show information about the volume groups.

vgrename

Rename volume groups.

Example

Explanation

fileserver fileserver_new

change volume group name to fileserver_new

lvcreate

Create a logical volume.

Usage

Explanation

–name <NAME> –size <SIZE>G <VOLUME_GROUP>

create a new logical volume

-l 100%FREE –thinpool <LOGICAL_VOLUME> <VOLUME_GROUP>

create a thin provisioning pool to allow for more efficient snapshots

-s <VOLUME_GROUP>/<LOGICAL_NAME>

create a snapshot of a logical volume (this can be restored at a later point in time)

Example

Explanation

–name media –size 30G fileserver

create a logical volume to be used as a virtual drive/partition

-L30G -s -n newsnapshot /dev/fileserver/media

create a 30GB snapshot of the media logical volume

-V 4G –thin -n <NEW_LOGICAL_VOLUME> <VOLUME_GROUP>/<LOGICAL_VOLUME>

create a logical thin volume within a logical thin pool (does not fully allocate the space, allows for over-allocating resources)

lvrename

Rename logical volumes.

Usage

Explanation

<VOLUME_GROUP> <LOGICAL_VOLUME_NAME> <NEW_LOGICAL_VOLUME_NAME>

lvresize

Resize logical volumes.

Usage

Explanation

-r

resize the filesystem

-L

size in M(B) or G(B)

-l 100%FREE

expand to use all available free space

lvextend

Increase the size of logical volumes.

Usage

Explanation

-L

size in M(B) or G(B)

Example

Explanation

-L55.5G /dev/fileserver/media

increases LV size of media by 55.5 gigabytes

–extents +100%FREE lv_example

extend the LV lv_example to utilize all of the available space in VG

lvreduce

Decrease the size of a logical volume.

Usage

Explanation

-L

size in M(B) or G(B)

lvremove

Remove logical volumes.

lvconvert

Restore a snapshot.

Usage

Explanation

–merge <LOGICAL_VOLUME_SNAPSHOT>

the original logical volume will be restored to this specified snapshot

lvchange

Usage

Explanation

-ay <VOLUME_GROUP>/<LOGICAL_VOLUME>

activate a logical volume

-an <VOLUME_GROUP>/<LOGICAL_VOLUME>

deactivate a logical volume

Boot Loaders

grub-customizer

A GUI for modifying GRUB boot entries.

gnome-disks

Package: gnome-disk-utility

Provides a GUI for modifying disk partitions

grub2-mkconfig

A utility to dynamically rebuild the GRUB 2 configuration based on the installed kernels and GRUB settings. On Fedora, the utility is grub2-mkconfig. On other operating systems it is grub-mkconfig.

Usage

Explanation

-o

output the GRUB configuration to a specified file

Example

Explanation

-o /boot/grub2/grub.cfg

rebuild the GRUB2 BIOS configuration on RHEL 7 and Fedora

-o /boot/grub/grub.cfg

rebuild the GRUB2 BIOS or UEFI configuration on Arch Linux

-o /boot/efi/EFI/redhat/grub.cfg

rebuild the GRUB2 UEFI config on RHEL 7

-o /boot/efi/EFI/fedora/grub.cfg

rebuild the GRUB2 UEFI config on Fedora

grub-update

Update the GRUB bootloader data on the start of the storage device.

grubby

Update the GRUB configuration with new settings.

Example

Explanation

–info=ALL

show information about all of the GRUB menu entries

–default-kernel

show the default kernel that will boot

–set-default <KERNEL_PATH_OR_MENU_ENTRY_NAME_OR_MENU_ENTRY_INDEX>

set a new default kernel

–add-kernel <KERNEL_PATH>

add a GRUB entry for the new kernel

–remove-kernel <KERNEL_PATH_OR_MENU_ENTRY_NAME_OR_MENU_ENTRY_INDEX>

remove the GRUB entry for the specified kernel

–args=<ARGS>

add new kernel boot arguments

–remove-args=<ARGS>

remove existing kernel boot arguments if found

–update-kernel=ALL

make changes to all GRUB entries

–update-kernel <KERNEL_PATH_OR_MENU_ENTRY_NAME_OR_MENU_ENTRY_INDEX>

make changes to a specific kernel GRUB entry

–[grub|lilo|silo|yaboot|zipl]

specify the bootloader configuration to modify (default is GRUB)

(GRUB Rescue Prompt)

If GRUB fails to boot, a grub rescue> prompt is presented to the end-user.

Usage

Explanation

insmod normal; normal

this will load the kernel module for the GUI GRUB prompt

blkid

list partitions and their UUIDs

ls

list the partitions; this can also be used to view files in the partition

busybox

busybox is sometimes provided to have common shell utilities available

dracut

Rebuild the initramfs on Fedora.

Usage

Explanation

rebuild the initramfs for the current running kernel; optionally specify a kernel version

-f, –force

replace the initramfs if it already exists

–add-drivers

a list of kernel modules to append to the default modules

–drivers

a specific list of kernel modules to compile into the initramfs

–list-modules

show all Dracut modules

–add

Dracut modules to add, appending the default modules

–driver

a specific list of Dracut modules to add

–omit-drivers

specify a list of kernel modules to exclude

–install

a list of files to add

–compress {gzip|bzip2|lzma|xz|lzo|lz4}

specify the type of compression to use; default is gzip

–kernel-image

the kernel image file to use

Ceph

ceph-deploy

Install and manage Ceph.

Usage

Explanation

install –release <RELEASE> <SERVER1> <SERVER2>

install or upgrade the release version of Ceph (see http://docs.ceph.com/docs/master/releases/) on the specified servers

mon create-initial

install the Ceph monitor services on the local node

disk list <SERVER1>

show all available disks on a specified server

disk zap <SERVER1>:<DRIVE1>

remove the partition table off of the specified server’s drives

osd create <SERVER1>:<DRIVE1>

prepare the drives; two partitions are created, a (1) data and (2) journal partition

Example

Explanation

disk zap node1:sdc

wipe the sdc drive from node1

ceph

Usage

Explanation

auth list

show users and their permissions

status

show information about the Ceph cluster

mon {stat|dump}

show the status of the Ceph monitoring services

tell osd.* version

show the Ceph version on the OSD nodes

tell mon.* version

show the Ceph version on the monitor nodes

osd pool ls

list all created pools

health

show the health status of the cluster

health detail

show a more detailed report of any issues

pg repair <PG>

fix inconsistencies within a placement group

osd <POOL> set data size <COUNT>

set the total number of all objects (replicas and the original file) that should be created per object

osd pool get <POOL> <KEY>

get the current value for the key for a specific pool

osd pool get rbd size

show the replica count

pg dump

display the placement group map

osd dump

display the OSD map

osd tree

show OSD weights and brief status

osd pool create <NAME> <PG_NUM> <PGP_NUM>

create a new pool in Ceph

osd pool get volumes size

show volume sizes

osd pool set volumes size <INTEGER>

set volumes size

ceph-osd

Usage

Explanation

-i

specify the OSD drive number

–flush-journal

flush the journal to the disk

rbd

Usage

Explanation

{ls|list}

show block devices in a specified pool

rm <DEVICE> -p <POOL>

delete a device from a pool

export <POOL>/<VOLUME> –path <FILE>.img

download the block image

snap ls <POOL>/<VOLUME>

show all snapshots for a block device

snap purge

remove all snapshots

snap protect

prevent a snapshot from being deletable

snap unprotect

allow a snapshot to be deleted

create <POOL>/<IMAGE> –size <SIZE_IN_MB>

create a new RBD image

map <POOL>/<IMAGE>

map an RBD image to a client server as a block device

feature disable imagename deep-flatten fast-diff object-map exclusive-lock

disable all of the new RBD features for an image that are new to the Jewel release; these require the Linux 4.8 kernel or newer

rbd snap purge <POOL>/<VOLUME_ID>@<SNAPSHOT>

remove a snapshot

rados

Usage

Explanation

lspools

view RADOS pools

df

show Ceph disk usage

-p <POOL> ls

show raw PG files that are part of a pool

iSCSI

targetcli (interactive)

Create iSCSI targets.

Usage

Explanation

ls

view the current configuration tree

cd

change to a different path

saveconfig

save the configuration

restoreconfig

restore a specified configuration file

clearconfig

delete the current configuration

help

view help output

Variables

Explanation

auto_save_on_exit

run saveconfig on exit; default: True

confirm

allow the configuration to be cleared; default: False

iscsiadm

Package: iscsi-initiator-utils

Usage

Explanation

–mode discoverydb –type sendtargets –portal <IPADDRESS> –discover

search for iSCSI targets at a given address

iscsiadm –mode node –targetname <TPG> –portal <IPADDRESS> –login

attach the target portal group

Windows Partitioning

These are utilities to manage Windows file systems from UNIX-like operating systems.

fatresize

Resize FAT file systems.

mkdosfs

Package: dosfstools

Manage DOS filesystems.

Usage

Explanation

-F 16

format a partition to FAT16

mkfs.ntfs

Create NTFS file systems.

Usage

Explanation

-Q

quickly formats 1 partition to NTFS on a device

mount -t ntfs-3g

Package: ntfs-3g

Mount NTFS file systems. The Windows operating system had to have been cleanly and fully shutdown first by running shutdown /s /f /t 0 from Windows.

ms-sys

Utility for creating Windows Master Boot Records (MBR).

Usage

Explanation

–fat32

create a FAT32 DOS MBR

-7

create a Windows 7 MBR