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RHCSA 7 > Configure local Storage > Flashcards

Configure local Storage Flashcards

1
Q

/dev

A

All system devices are located in /dev

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2
Q

To create a new partition using fdisk

A

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
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3
Q

partprobe command

A 
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
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4
Q

Parted command

A

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

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5
Q

Example of a swap partition with 2GB

A

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

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6
Q

To set the first partition as bootable in parted

A

(parted) set 1 boot on

type set 1 boot off to remove the bootable flag

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7
Q

parted remove a partition

A

(parted) rm 2

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8
Q

LVM

A

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)
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9
Q

Creating Logical volume

A

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 entercommand
(m for help): t
- next type (L) to view the different hex code, then press entercommand
(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 savecommand
(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
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10
Q

To grow a logical volume

A

lvresize -L 900 MB /dev/vg_new/lv_new

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11
Q

to shrink the logical volume

A 
# resize2fs /dev/vg_new/lv_new 800MB
# lvresize -L 800MB /dev/vg_new/lv_new
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12
Q

to remove a volume from a volume group

A

pvremove /dev/sdb1

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13
Q

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

A

vgextend myvolgroup /dev/sdc

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14
Q

to assign a new physical volume to an existing volume

A

vgextend myvolgroup /dev/sdd

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15
Q

to remove a physical volume from a volume group

A

vgreduce myVolGroup /dev/sdc

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16
Q

to delete logical volumes

A

lvremove /dev/myVolGroup/vol0

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17
Q

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

A

lvmdiskscan

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18
Q

pvscan command

A 
scans all supported LVM block devices in the system for physical volumes. It shows all physical devices found
#pvscan
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19
Q

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

A 
# pvchange -x n /dev/sdc1
you can use the -xy arguments of the pvchange command to allow allocation where it had previously been disallowed
20
Q

to resize a physical volume

A

you should use the pvresize command

21
Q

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

A

vgchange -l 128 /dev/vg00

22
Q

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

A

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

23
Q

To remove a volume group that contains no logical volumes

A

vgremove officeVG

24
Q

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

A 
use vgsplit command. Logical volumes cannot be split between volume groups
 # vgsplit bigvg smallvg /dev/ram15
25
Q

to combine volume groups

A

vgmerge -v databases my-vs

26
Q

renaming an existing volume group vg02 to my_volume_group

A 
# vgrename /dev/vg02 /dev/my_volume_group
# vgrename vg02 my_volume_group
27
Q

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

A

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

28
Q

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

A

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

29
Q

to create a mirror volume

A

lvcreate -L 50G -ml -n mirrorlv vg0

30
Q

steps to create a snapshot of a logical volume

A 
# 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 createdto restore data from a snapshot, you need to first mount it
# mount -t ext4 /dev/vg-new/lvsnapshot /mnt/snapshotThen you can copy the data back rom /mnt/snapshot
31
Q

to remove a snapshot

A 
# umount /mnt/snapshot
# lvremove /dev/vg-new/mvsnapshot
32
Q

GUI to manage LVM

A 
System-config-lvm not installed by default
# yum install system-config-lvm
to access you can call from the terminal or from the GUISystem - Administration - logical volume Management
33
Q

to find the UUID of a device

A 
#blkid
you can also use this command
# dump2fs /dev/sdb1 | grep UUID
34
Q

add UUID to /etc/fstab

A 
# vi /etc/fstab
add entry similarUUID=[strings of numbers & letters obtained] /mydata ext4 defaults 1 2
35
Q

To label a filesystem

A 
#e2label /dev/mapper/data luksdrive
then you can add entry to /etc/fstabLABEL=luksdrive /mydata ext4 defaults 1 2
You can also assign a label to a disk with this command
#tune2fs -L test /dev/sdb1other commands
# mke2fs -L newlabel /dev/hdb1
# mkfs.ext3 -L newlabel /dev/hdb1- mkswap -L swaplabel /dev/hdbxx
36
Q

Mounting a specific logical volume by UUID

A

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

37
Q

manually mounting filesystems can also be done via label

A

mount -L labelname /mnt/point1

38
Q

to display all partitions with their corresponding UUID and labels

A 
# blkid
# ls -l /dev/disk/by-uuid/
# tree /dev/disk 
On the graphical end, you can install gparted
# yum install gparted
39
Q

-adding a partition using fdisk(summarize)

A 
#fdisk /dev/sdb
2 - type p to print
3 - type 1
4 - hit enter twice
5 - type t
6 - type 82
7 - type w
40
Q

adding a logical volume fdisk(summarize

A 
#fdisk /dev/sdd
type p
type n
type 1
type t
type L
type 8e
type w
41
Q

to make a swap partition(summarize)

A 
# 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/...
42
Q

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

A 
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 /dev/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
43
Q

To unmount a LUKS-encrypted file system

A 
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/volTo 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/volRemove the logical volume
#lvremove /dev/vg/lv_volRemove the file where the passphrase is store
#rm /root/luks.keyEdit the /etc/crypttab and /etc/fstab files and remove the entries associated with the LUKS logical volume
44
Q

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

A

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/fstabLABEL=luksdrive /mynew_data ext4 defaults 1 2

45
Q

To create a volume group (here called vg using a physical volume /dev/vda) with a physical extent size of 8MB, type:

A

vgcreate -s 8m vg /dev/vda

46
Q

Alternatively, if you do not have a spare partition for swap, you can always use a file on existing one:

A
  1. Create an empty file on e.g. /mnt/ partition (size 50MB):

dd if=/dev/zero of=/mnt/swap.file bs=1M count=50
chmod 0600 /mnt/swap.file

  1. Set up a Linux swap area on that file:

mkswap /mnt/swap.file

  1. Add an entry to your /etc/fstab file:

/mnt/swap.file swap swap 0 0

  1. Enable newly added swap area:

swapon -a

  1. Check if the system is using it:

swapon -s

RHCSA 7 (10 decks)

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