Configure Local Storage

Question 1

/dev

Answer 1

All system devices are located in /dev

Question 2

To create a new partition using fdisk

Answer 2

fdisk /dev/sdb

• use m -> for help
• use p -> to print
• use n -> to create a partition
• use L -> to view different file system we can use
• use w -> to write changes

Question 3

partprobe command

Answer 3

If you don't see the partition that was just created, you can reboot the system or use the partprobe command
# partprobe
Which tells the kernel to re-read all partition

Question 4

Parted command

Answer 4

parted

(parted) print all or type # parted -l
(parted) select /dev/sdb
(parted) mktable gpt create a gpt partition tables

• to create a primary partition with the ext4 type(from 1 mb to 400GB)
  (parted) mkpart primary ext4 1MB 400GB
  (parted) rm 2 remove a partition
• to use all the remaining space, use -1 as end position
• If at a later stage, after creating a partition, you want to change the type of partition, don’t drop and recreate the partition. Format the partition as you want and parted will normally detect the new type

Question 5

Example of a swap partition with 2GB

Answer 5

(parted) mkpart primary linux-swap 400GB 402GB

Question 6

To set the first partition as bootable in parted

Answer 6

(parted) set 1 boot on

type set 1 boot off to remove the bootable flag

Question 7

parted remove a partition

Answer 7

(parted) rm 2

Question 8

LVM

Answer 8

Logical Volume Manager. It is the default volume management system

• Uses a collection of disks
• a single volue can span multiple disks
• not all disks need to be the same size
• each disk is referred to as a ‘Physical Volume’ (PV)
• physical volumes are collected in to ‘volume groups’ (VG)
• A volume group is split into ‘logical volumes’ (LV)
• logical volumes contain the file systems
• LVM allows for online resizing, reduces system downtime
• PV’s and LV’s are broken up into chunks of data, called extents
• Logical volumes can be grown or shrunk by either increasing or decreasing the extents used, or by increasing or decreasing the amount of disk space used (MG, GB, etc)
• LVM provides the ability to create volume backups through snapshots(no need for filesystem downtime)
• the /boot partition cannot be on a logical volume, grub cannot real LVM volumes
• Volume groups are located at /dev/mapper command line and GUI tools (System-config-lvm)

Question 9

Creating Logical volume

Answer 9

First step is to convert any disk or partition into physical volumes
# fdisk /dev/sdb
- press the t key to change the partition’s type, then press enter
command(m for help): t
- next type (L) to view the different hex code, then press enter
command(m for help): L
- The one for LVM is 8e, so enter 8e and press enter
hex code(type L to list codes): 8e
-type w to save
command (m for help): w

-step 2 create a physical volume:
# pvcreate /dev/sdb1
- to check on the physical volume:
# pvs
- to view more details:
#pvdisplay

- step 3 lump volumes into a volume group
# vgcreate vg_new /dev/sdb1 /dev/sdc1
- to check on the volume group
# vgs
# vgdisplay

• step 4 create logical volume
  # lvcreate -L 800M -n lv_new vg_new
• to verify
  # lvs

Question 10

To grow a logical volume

Answer 10

lvresize -L 900 MB /dev/vg_new/lv_new

Question 11

to shrink the logical volume

Answer 11

# resize2fs /dev/vg_new/lv_new 800MB
# lvresize -L 800MB /dev/vg_new/lv_new

Question 12

to remove a volume from a volume group

Answer 12

pvremove /dev/sdb1

Question 13

if the volume doesn’t exist, you can create it and add physical volumes in one shot

Answer 13

vgextend myvolgroup /dev/sdc

Question 14

to assign a new physical volume to an existing volume

Answer 14

vgextend myvolgroup /dev/sdd

Question 15

to remove a physical volume from a volume group

Answer 15

vgreduce myVolGroup /dev/sdc

Question 16

to delete logical volumes

Answer 16

lvremove /dev/myVolGroup/vol0

Question 17

you can scan for block devices that can be used as physical volumes

Answer 17

lvmdiskscan

Question 18

pvscan command

Answer 18

scans all supported LVM block devices in the system for physical volumes. It shows all physical devices found
#pvscan

Question 19

The following command disallows the allocation of physical extents on /dev/sdc1

Answer 19

# pvchange -x n /dev/sdc1
you can use the -xy arguments of the pvchange command to allow allocation where it had previously been disallowed

Question 20

to resize a physical volume

Answer 20

you should use the pvresize command

Question 21

To change the maximum number of logical volumes of volume group vg00 to 128

Answer 21

vgchange -l 128 /dev/vg00

Question 22

The following will deactivate the volume group my-volume-group

Answer 22

vgchange -a n my-volume-group volume group are activated by default

Question 23

To remove a volume group that contains no logical volumes

Answer 23

vgremove officeVG

Question 24

to split the physical volumes of a volume group and create a new volume group

Answer 24

use vgsplit command. Logical volumes cannot be split between volume groups 
# vgsplit bigvg smallvg /dev/ram15

Question 25

to combine volume groups

Answer 25

vgmerge -v databases my-vs

Question 26

renaming an existing volume group vg02 to my_volume_group

Answer 26

``` # vgrename /dev/vg02 /dev/my_volume_group # vgrename vg02 my_volume_group ```

Question 27

Creating a striped logical volume across 2 physical volumes with a stripe of 64 KB

Answer 27

lvcreate -L 50G -i2 -I64 -n gfslv vg0 gfslv is the name of LV, while vg0 is the name of the VG

Question 28

An example where the stripe will use sectors 0-50 of /dev/sda1 and sectors 50-100 of /dev/sdb1

Answer 28

#lvcreate -l 100 -i2 -nstripelv testvg /dev/sda1:0-50 /dev/sdb1:50-100

Question 29

to create a mirror volume

Answer 29

lvcreate -L 50G -ml -n mirrorlv vg0

Question 30

steps to create a snapshot of a logical volume

Answer 30

mkdir /mnt snapshot directory to mount the snapshot # lvcreate -L 100M -s -n lvmsnapshot /dev/vg-new/lv-new creates the snapshot # lvs to view the snapshot created to restore data from a snapshot, you need to first mount it # mount -t ext4 /dev/vg-new/lvsnapshot /mnt/snapshot Then you can copy the data back rom /mnt/snapshot

Question 31

to remove a snapshot

Answer 31

``` # umount /mnt/snapshot # lvremove /dev/vg-new/mvsnapshot ```

Question 32

GUI to manage LVM

Answer 32

System-config-lvm not installed by default # yum install system-config-lvm to access you can call from the terminal or from the GUI System - Administration - logical volume Management

Question 33

to find the UUID of a device

Answer 33

``` #blkid you can also use this command # dump2fs /dev/sdb1 | grep UUID ```

Question 34

add UUID to /etc/fstab

Answer 34

``` # vi /etc/fstab add entry similar UUID=[strings of numbers & letters obtained] /mydata ext4 defaults 1 2 ```

Question 35

To label a filesystem

Answer 35

``` #e2label /dev/mapper/data luksdrive then you can add entry to /etc/fstab LABEL=luksdrive /mydata ext4 defaults 1 2 ``` ``` You can also assign a label to a disk with this command #tune2fs -L test /dev/sdb1 ``` other commands # mke2fs -L newlabel /dev/hdb1 # mkfs.ext3 -L newlabel /dev/hdb1 - mkswap -L swaplabel /dev/hdbxx

Question 36

Mounting a specific logical volume by UUID

Answer 36

blkid | grep lv_vol >> /etc/fstab - then edit /etc/fstab the lvdisplay command also generates the UUID of a logical volume # lvdisplay logicalVolumeName | grep UUID

Question 37

manually mounting filesystems can also be done via label

Answer 37

mount -L labelname /mnt/point1

Question 38

to display all partitions with their corresponding UUID and labels

Answer 38

``` # blkid # ls -l /dev/disk/by-uuid/ # tree /dev/disk ``` ``` On the graphical end, you can install gparted # yum install gparted ```

Question 39

-adding a partition using fdisk(summarize)

Answer 39

``` #fdisk /dev/sdb 2 - type p to print 3 - type 1 4 - hit enter twice 5 - type t 6 - type 82 7 - type w ```

Question 40

adding a logical volume fdisk(summarize

Answer 40

``` #fdisk -cu /dev/sdd type p type n type 1 type t type L type 8e type w ```

Question 41

to make a swap partition(summarize)

Answer 41

mkswap /dev/sdc1 to activate: #swapon /dev/sdc1 to check it #swapon -s ``` Add it to /etc/fstab #echo "/dev/sdc1 swap swap defaults 0 0" >> /etc/fstab ``` ``` to remove swap logical volume # swapoff /dev/... ```

Question 42

Create and configure LUKS-encrypted partitions and logical volumes to prompt for password and mount a decrypted file system at boot

Answer 42

``` Install the LUKS package #yum install -y cryptsetup-luks ``` ``` Activate LUKS module #modprobe dm_crypt ``` ``` Check the module is running #lsmod | grep dm_crypt ``` ``` Create a logical volume(here called lv_vol with a size of 100MB in the vg volume group) #lvcreate --size 100M --name -v_vol vg ``` ``` Convert the new logical volume to the LUKS format: #cryptsetup luksFormat /dev/vg/lv_vol ``` ``` Open and give a name to the LUKS logical volume (here vol): #cryptsetup luksOpen /dev/vg/lv_vol vol ``` ``` Create an EXT4 file system on the LUKS logical volume #mkfs.ext4 /dev/mapper/vol ``` Create the /etc/crypttab file and add the following line: vol /dev/vg/lv_vol /root/luks.key Note: if you put 'none' instead of '/root/luks.key', you will be asked for the passphrase at each boot at the console Create the /root/luks.key file for example to store the passphrase: mypassphrase ``` Add the passphrase to the LUKS logical volume #cryptsetup luksAddKey /vdev/vg/lv_vol /root/luks.key ``` edit /etc/fstab file and add the following line (be careful when editing the /etc/fstab file or configure a virtual console): /dev/mapper/vol /vol ext4 defaults 1 2 ``` Create the mount point #mkdir /vol ``` ``` Mount the LUKS logical volume #mount /vol ```

Question 43

To unmount a LUKS-encrypted file system

Answer 43

``` Unmount a LUKS-encryted file system by its mounting point in the /etc/fstab file (here /vol), #unmount /vol ``` ``` To unmount a LUKS-encrypted file system by its LUKS name (here vol), type: #umount /dev/mapper/vol ``` To remove a LUKS-encrypted file system, follow: unmount the LUKS file system (here /vol): #umount /vol ``` Close the LUKS logical volume: #cryptsetup luksClose /dev/mapper/vol ``` ``` Remove the logical volume #lvremove /dev/vg/lv_vol ``` ``` Remove the file where the passphrase is store #rm /root/luks.key ``` Edit the /etc/crypttab and /etc/fstab files and remove the entries associated with the LUKS logical volume

Question 44

Configure Systems to mount file systems at boot by Universally Unique ID (UUID) or label

Answer 44

Find the UUID of a devide #blkid once found enter in /etc/fstab UUID=f8b69..... /mynew_data ext4 defaults 1 2 ``` Then mount #mount -a ``` ``` To mount using a label, first you need to create the label #e2label /dev/mapper/mynew_data luksdrive ``` Then add to /etc/fstab LABEL=luksdrive /mynew_data ext4 defaults 1 2