Mounting and Unmounting File Systems

Mounting File Systems Manually

mount <file_system>

• There are two ways to specify file_system on a disk partition

• name of device in /dev
• uuid

Command lsblk list the details of block devices available

/mnt is the a temporary mount point

Mounting by UUID

• use lsblk -fp to get the full path and uuid of devices

mount UUID="3242424-4242-4242424" /mnt/data

• use fdisk -l to view disks currently on your machine

Automatic mounting of Removable Storage Devices

if on GUI, removable device is mounted at /run/media/<USER>/<LABEL>.

Unmounting File Systems

• shutdown unmounts all file systems automatically to unmount a file system

umount /mnt/data # if pwd is /mnt/data, it will error because shell is still using the directory as current wd.

• lsof list all open files and processes accessing them. Useful for finding which process is preventing umount

lsof /mnt/data

parted /dev/<id> print 
parted /dev/<id> mklabel gpt # make a gpt partition table
i) parted /dev/<id>
ii) mkpart # to make a new partition

#alternative one-liner
parted /dev/<id> mkpart <name> xfs 2048s 1000MB # parted device mkpart name fs_type start_sector end_sector

udevadm settle # to wait for system to detect the new partition and to create the ass. device file under the /dev

Deleting Partitions

parted
print
rm <number>

Creating File Systems

there are two common file systems in rhel “xfs” and “ext4” mkfs.xfs /dev/sdb

Mounting File Systems

we have looked at the manual way of mounting file system

mount <device> <location>

Managing Swap Space

• an area of a disk under the control of the Linux kernel memory management subsystem. The kernel uses swap space to supp. the system RAM by holding inactive pages of memory. The combined system RAM plus swap space is called virtual memory.
• RAM and swap space recommendations

Creating a swap space

• create a partition with a fs type of linux-swap

parted /dev/sdb
print
mkpart
> swap1 # name
> linux-swap # fs type
> 1001MB # start
> 1257MB # end

$ udevadm settle # to wait for the partition to be created

• creating a swap signature to the device

mkswap /dev/sdb2 # to setup swapspace

Activating a Swap space

free OR swapon --show # to inspect the available swap spaces.
swapon /dev/sdb2 # swapoff deactivates a swapspace 
free

• the /etc/fstab file is where configurations about disks and swap spaces are loaded from start time of the machine.
  UUID=<uuid> swap swap defaults 0 0

Setting the swap space priority

by default the system uses swap spaces in series. However, swap spaces until it is full, then it uses the second swap space. However, you can define a priority for each swap space to force that order. the default is -2.

UUID=adsfdsfdsafdsafsdf swap swap pri=4  0 0  
UUID=asdfsdafsdafsdfsda swap swap pri=10 0 0  

• the highest priority is used.