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.

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

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)

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 

gnome-disks 

Package: gnome-disk-utility

Provides a GUI for modifying disk partitions

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 GRUB 2 BIOS configuration on Fedora
-o /boot/grub/grub.cfg	rebuild the GRUB 2 BIOS and UEFI configuration on Arch Linux or Debian

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

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

History 

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