To mount USB mass storage device on CentOS 7, you need to add a package repository first and install some exfat utilities.

Check your attached devices by fdisk

In my case, I am planning to mount 10T Harddisk, and it it shown as 9.1T in /dev/hda2 like below when I run fdisk -l

# fdisk -l
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.

Disk /dev/sda: 10000.8 GB, 10000831348736 bytes, 19532873728 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: gpt
Disk identifier: 8EEF9C29-5082-4436-AF97-D99E6C49C7B0


#         Start          End    Size  Type            Name
 1           34       262177    128M  Microsoft reser Microsoft reserved partition
Partition 1 does not start on physical sector boundary.
 2       264192  19532871679    9.1T  Microsoft basic Basic data partition
WARNING: fdisk GPT support is currently new, and therefore in an experimental phase. Use at your own discretion.

Disk /dev/sdb: 2000.4 GB, 2000398934016 bytes, 3907029168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disk label type: gpt
Disk identifier: E453250C-A828-43E8-AC48-CBE474111F11


#         Start          End    Size  Type            Name
 1         2048       411647    200M  EFI System      EFI System Partition
 2       411648      2508799      1G  Microsoft basic
 3      2508800   3907028991    1.8T  Linux LVM

Disk /dev/mapper/centos-root: 1982.3 GB, 1982261624832 bytes, 3871604736 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes


Disk /dev/mapper/centos-swap: 16.8 GB, 16844324864 bytes, 32899072 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes


Install exfat utilities

In order to mount that device in exfat, you will need to add package repository for exfat as following

# sudo yum install -y http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-1.el7.nux.noarch.rpm

Once you run above command, you will see below

Loaded plugins: fastestmirror
nux-dextop-release-0-1.el7.nux.noarch.rpm                                                                                      | 9.6 kB  00:00:00
Examining /var/tmp/yum-root-LUgBEg/nux-dextop-release-0-1.el7.nux.noarch.rpm: nux-dextop-release-0-1.el7.nux.noarch
Marking /var/tmp/yum-root-LUgBEg/nux-dextop-release-0-1.el7.nux.noarch.rpm to be installed
Resolving Dependencies
--> Running transaction check
---> Package nux-dextop-release.noarch 0:0-1.el7.nux will be installed
--> Finished Dependency Resolution

Dependencies Resolved

======================================================================================================================================================
 Package                            Arch                   Version                       Repository                                              Size
======================================================================================================================================================
Installing:
 nux-dextop-release                 noarch                 0-1.el7.nux                   /nux-dextop-release-0-1.el7.nux.noarch                 3.5 k

Transaction Summary
======================================================================================================================================================
Install  1 Package

Total size: 3.5 k
Installed size: 3.5 k
Downloading packages:
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : nux-dextop-release-0-1.el7.nux.noarch                                                                                              1/1
  Verifying  : nux-dextop-release-0-1.el7.nux.noarch                                                                                              1/1

Installed:
  nux-dextop-release.noarch 0:0-1.el7.nux

Complete!


Once you added the repository, you can install it as following

# sudo yum install -y exfat-utils fuse-exfat

Followings are the ouputs in my case

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
epel/x86_64/metalink                                                                                                           | 9.1 kB  00:00:00
 * base: mirror.opensourcelab.co.kr
 * epel: fedora.cs.nctu.edu.tw
 * extras: mirror.opensourcelab.co.kr
 * nux-dextop: mirror.li.nux.ro
 * remi-safe: mirrors.thzhost.com
 * updates: mirror.opensourcelab.co.kr
base                                                                                                                           | 3.6 kB  00:00:00
epel                                                                                                                           | 4.7 kB  00:00:00
extras                                                                                                                         | 2.9 kB  00:00:00
mysql-connectors-community                                                                                                     | 2.5 kB  00:00:00
mysql-tools-community                                                                                                          | 2.5 kB  00:00:00
mysql57-community                                                                                                              | 2.5 kB  00:00:00
nux-dextop                                                                                                                     | 2.9 kB  00:00:00
remi-safe                                                                                                                      | 3.0 kB  00:00:00
updates                                                                                                                        | 2.9 kB  00:00:00
(1/8): mysql-connectors-community/x86_64/primary_db                                                                            |  62 kB  00:00:00
(2/8): mysql-tools-community/x86_64/primary_db                                                                                 |  76 kB  00:00:00
(3/8): mysql57-community/x86_64/primary_db                                                                                     | 224 kB  00:00:00
(4/8): updates/7/x86_64/primary_db                                                                                             | 3.0 MB  00:00:00
(5/8): epel/x86_64/updateinfo                                                                                                  | 1.0 MB  00:00:00
(6/8): remi-safe/primary_db                                                                                                    | 1.7 MB  00:00:01
(7/8): epel/x86_64/primary_db                                                                                                  | 6.8 MB  00:00:02
(8/8): nux-dextop/x86_64/primary_db                                                                                            | 1.8 MB  00:00:02
Resolving Dependencies
--> Running transaction check
---> Package exfat-utils.x86_64 0:1.2.7-1.el7.nux will be installed
---> Package fuse-exfat.x86_64 0:1.2.7-1.el7.nux will be installed
--> Processing Dependency: libfuse.so.2(FUSE_2.6)(64bit) for package: fuse-exfat-1.2.7-1.el7.nux.x86_64
--> Processing Dependency: libfuse.so.2(FUSE_2.5)(64bit) for package: fuse-exfat-1.2.7-1.el7.nux.x86_64
--> Processing Dependency: libfuse.so.2(FUSE_2.2)(64bit) for package: fuse-exfat-1.2.7-1.el7.nux.x86_64
--> Processing Dependency: libfuse.so.2()(64bit) for package: fuse-exfat-1.2.7-1.el7.nux.x86_64
--> Running transaction check
---> Package fuse-libs.x86_64 0:2.9.2-11.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

======================================================================================================================================================
 Package                             Arch                           Version                                  Repository                          Size
======================================================================================================================================================
Installing:
 exfat-utils                         x86_64                         1.2.7-1.el7.nux                          nux-dextop                          58 k
 fuse-exfat                          x86_64                         1.2.7-1.el7.nux                          nux-dextop                          39 k
Installing for dependencies:
 fuse-libs                           x86_64                         2.9.2-11.el7                             base                                93 k

Transaction Summary
======================================================================================================================================================
Install  2 Packages (+1 Dependent package)

Total download size: 190 k
Installed size: 574 k
Downloading packages:
(1/3): fuse-libs-2.9.2-11.el7.x86_64.rpm                                                                                       |  93 kB  00:00:00
warning: /var/cache/yum/x86_64/7/nux-dextop/packages/fuse-exfat-1.2.7-1.el7.nux.x86_64.rpm: Header V4 RSA/SHA1 Signature, key ID 85c6cd8a: NOKEY2 ETA
Public key for fuse-exfat-1.2.7-1.el7.nux.x86_64.rpm is not installed
(2/3): fuse-exfat-1.2.7-1.el7.nux.x86_64.rpm                                                                                   |  39 kB  00:00:01
(3/3): exfat-utils-1.2.7-1.el7.nux.x86_64.rpm                                                                                  |  58 kB  00:00:01
------------------------------------------------------------------------------------------------------------------------------------------------------
Total                                                                                                                 108 kB/s | 190 kB  00:00:01
Retrieving key from file:///etc/pki/rpm-gpg/RPM-GPG-KEY-nux.ro
Importing GPG key 0x85C6CD8A:
 Userid     : "Nux.Ro (rpm builder) <rpm@li.nux.ro>"
 Fingerprint: 561c 96bd 2f7f dc2a db5a fd46 e98b fbe7 85c6 cd8a
 Package    : nux-dextop-release-0-1.el7.nux.noarch (@/nux-dextop-release-0-1.el7.nux.noarch)
 From       : /etc/pki/rpm-gpg/RPM-GPG-KEY-nux.ro
Running transaction check
Running transaction test
Transaction test succeeded
Running transaction
  Installing : fuse-libs-2.9.2-11.el7.x86_64                                                                                                      1/3
  Installing : fuse-exfat-1.2.7-1.el7.nux.x86_64                                                                                                  2/3
  Installing : exfat-utils-1.2.7-1.el7.nux.x86_64                                                                                                 3/3
  Verifying  : fuse-libs-2.9.2-11.el7.x86_64                                                                                                      1/3
  Verifying  : exfat-utils-1.2.7-1.el7.nux.x86_64                                                                                                 2/3
  Verifying  : fuse-exfat-1.2.7-1.el7.nux.x86_64                                                                                                  3/3

Installed:
  exfat-utils.x86_64 0:1.2.7-1.el7.nux                                       fuse-exfat.x86_64 0:1.2.7-1.el7.nux

Dependency Installed:
  fuse-libs.x86_64 0:2.9.2-11.el7

Complete!


Format and label

Format in exfat

# mkfs.exfat /dev/sda2

Once formatting is started, you will see below results

mkexfatfs 1.2.7
Creating... done.
Flushing... done.
File system created successfully.

Give label to partition as following - this is very import !!

# exfatlabel /dev/sda2 EX_PART


Mount

Create a folder in some nice location

# mkdir /mnt/10T

And you can simply mount it as following

mount /dev/sda2 /mnt/10T

Auto-mount USB mass storage while booting

The first thing what I tried is to get UUID for the required disk partition by ls -al /dev/disk/by-uuid/ as following

# ls -al /dev/disk/by-uuid/

Then you will see the table like below

drwxr-xr-x 2 root root 140 Jul 13 13:58 .
drwxr-xr-x 8 root root 160 Jul 13 13:58 ..
lrwxrwxrwx 1 root root  10 Jul 13 13:58 0C80-DEDB -> ../../sda1
lrwxrwxrwx 1 root root  10 Jul 13 13:58 2e3fddc0-f6db-4b5b-a4b1-f8cd51da5095 -> ../../dm-1
lrwxrwxrwx 1 root root  10 Jul 13 13:58 8a27fe79-e520-4eff-bf2d-69088cb95b83 -> ../../dm-0
lrwxrwxrwx 1 root root  10 Jul 13 13:58 9096-6D1E -> ../../sdb2
lrwxrwxrwx 1 root root  10 Jul 13 13:58 dd68fbad-bf99-4fd7-aee4-76fb8c0323f9 -> ../../sda2

In my case, I tried to mount /dev/sda2 above and its UUID is 636e9a0f-5fdf-43ca-8158-8f1af0a84f29, and I it at /etc/fstab like below:

UUID=9096-6D1E 	/mnt/10T	ext4	defaults	0 0

What I intended is to mount the partition having the UUID like above to /mnt/10T, and it worked as I wanted.