RHCSA7 Exam Notes #3: Configure local storage

Word version available here:
https://drive.google.com/file/d/0B9WPh0iDN4KwM0ptNTlXWnlPcDQ/edit?usp=sharing
 

List, create, delete partitions on MBR and GPT disks

MBR older method used with BIOS computers < 2.2TB, 4 Primary Partitions Max, < 12 logical partitions per drive recommended

GPT part of UEFI standard, < 2 ZetaBytes, 128 Primary Partitions

/dev/xxyN        (/device file directory/xx=type of device -usually sd, y=which device, N=partition number – first 4 are for primary/extended – logical partitions start at 5 and upwards)

Disk Partitions are mounted to a Directory to make them usable – i.e. if /dev/sda5 is mounted on /usr/ all files written under /usr/ would reside on /dev/sda5

Read: Linux 7 Installation Guide – section – “An Introduction to Disk Partitions” for an excellent primer in Linux Disk Partitions

Run command “parted /dev/sd[a-z]” with root privileges to target a particular disk with the following commands:

print                                        (lists partitions - number=partition number, i.e. 1 is /dev/sda1)

mklabel msdos                        (needed on all new disks)

mkpart primary ext3 1 2001  (creates a primary partition with an ext3 filesystem from 1MB to 2001MB on disk)

You can also just use the mklabel and mkpart commands on their own and step through the prompts. Next: Exit parted with q

partprobe /dev/sdc                 (force the kernel to re-read the updated partition table)

parted /dev/sdc print                          (check partitions)

/usr/sbin/mkfs –t ext3 /dev/sdc1       (create the file system)

Now give the partition a label to help identify the associated mount point to create later:

e2label /dev/sdc1 /work        

mkdir /work                                        (creates /work directory)

partprobe /dev/sdc                             (force kernel to re-read updated partition table)

mount /dev/sdc1 /work

Now to make the mount permanent:

blkid –o list      (gives list of UUIDs – use the terminal copy and paste commands here)

vi /etc/fstab    (edit to add new partition mount, use boot one as template but change xfs to ext3 as highlighted below!!)

UUID=XXXX /work ext3 defaults 1 2

“mount –a” to test and “mount | grep /work” to check

To remove unmounts the partitions and run “parted sdc” and list partitions with print

rm 1    (deletes partition 1)

Quit with q and edit /etc/fstab to remove the line added earlier. Reboot

Now if you run “cat /proc/partitions” you should no longer see sdc1

 

Create and remove physical volumes, assign physical volumes to volume groups, and create and delete logical Volumes

system-config-lvm was dropped with GNOME3 in RHEL7 so good luck finding that! All work has to be command line with LVM as a result.

 

 

Add a new disk to your test system. Reboot and check using “fdisk -l” what the name is, in my case it appeared as /dev/sdb

pvcreate /dev/sdb       (creates a partition on sdb to initialise the disk)
pvdisplay /dev/sdb      (Displays details of the physical volumes)

vgcreate -s 8 vg01 /dev/sdb   (creates vg01 volume group with 8MB PE size, can add other partitions also by appending /dev/sdc1 /dev/sdf etc to command)

vgdisplay -v vg01                    (displays details of vg01)
lvcreate -L 3000 -n dbvol vg01           (creates 3GB logical volume dbvol in volume group vg01)lvcreate -L 1500 -n myball vg01         (creates second logical volume)
lvdisplay -v vg01         (Displays details of vg01 volume group)

To Extend Space:
pvcreate /dev/sdc
vgextend vg01 /dev/sdc          (adds sdc to vg01 volume group)
lvextend -L +2GB /dev/vg01/dbvol     (extends dbvol by 2GB, or set absolute size with 5GB)
lvresize -L 2.5GB /dev/vg01/myball   (resizes myball to 2.5GB, or use + to add space, can also reduce space by lowering figure or using -1GB for instance)

Remove Volumes:
lvremove /dev/vg01/myball   (Do this for dbvol also then proceed to the next step)
vgreduce vg01 /dev/sdc /dev/sdb      (removes sdb/sdc from vg01)
vgremove vg01                                   (removes vg01)
pvremove /dev/sdb /dev/sdc              (removes sdb/sdc partitions)

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

rpm -qa | grep cryptsetup      (confirms encryption packages are install, should be by default)
I recreated the logical volumes used in the last section to test against:
cryptsetup -v -y luksFormat /dev/vg01/dbvol (ensure the F in luksFormat is uppercase!)
cryptsetup –v luksOpen /dev/vg01/dbvol dbvol_luks (ensure the O in luksOpen is uppercase! Assigns name to volume to create a device file in /dev/mapper directory)
ls -l /dev/mapper | grep dbvol_luks   (checks device is present in mapper file)
mkfs -t ext4 /dev/mapper/dbvol_luks            (construct ext4 file system in the logical volume)
mkdir /dbvol_luks       (create mount point)
mount /dev/mapper/dbvol_luks /dbvol_luks (mount file system, check with “df”)

edit /etc/crypttab file and add the following line:

dbvol_luks /dev/vg01/dbvol_luks none          (this will prompt for password on startup)

edit /etc/fstab and add the following line:
/dev/mapper/dbvol_luks /dbvol_luks ext4 defaults 1 2

Reboot, supply password on startup and check mount status:
mount | grep dbvol_luks

NOTE: when rebooting it hangs, tried volume group and partition but it’s not working out for me. Will troubleshoot and update when I have a stable config. (took out fstab from partition method and got prompted at gui!?!)

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

blkid -o list      (make sure you run this command as root, gives device UUIDs)
e2label /dev/sdb myball2       (labels partition myball2)
Use either of the two methods in /etc/fstab to mount file systems on bootup:
UUID=xxxx /home ext4 defaults 1 2
LABEL=myball2 /hiccup ext4 defaults 1 2

Add new partitions and logical volumes, and swap to a system non-destructively

parted /dev/sdb
mklabel / msdos / yes             (Assign a label to the disk, must be done on new disk)
mkpart / primary / [ext4/linux-swap] / 1 / 2g           (Create a ext4 / Swap partition of 2GB)print                                        (Verify)
partprobe /dev/sdb     (force kernel to re-read the updated partition table)
grep sdb /proc/partitions

mkswap /dev/sdc                                swapon /dev/sdc
mkswap /dev/vg01/myball                 swapon /dev/vg01/myball
swapon -s                    (confirm new swap areas are activated)

vmstat -s

Edit /etc/fstab to activate on system boot:
UUID=XXXX  swap   swap  defaults  0 0
/dev/vg01/myball  swap   swap  defaults 0 0
swapoff /dev/sdc                    swapoff /dev/vg01/myball

Edit /etc/fstab to remove swap entries and reboot to validate