CentOS or Red Hat Linux is a popular server operating system to the system administrators. Almost all the system admins or IT guys who play with mail server, file server, proxy server and so on are so known with CentOS or Red Hat Linux and cannot go a single day without this operating system. The guys who are also wish to be a system admin should be familiar with CentOS or Red Hat operating system. In my previous article, I discussed how to install CentOS 7 step by step with GUI mode (GNOME Desktop) or CLI mode (minimal installation). I also discussed how to configure network with nmtui tool as well as editing network files. In this article, I will discuss how to manage CentOS 7 or Red Hat 7 Linux partition with the fdisk tool. But before going to start, we should have some basic idea on the following terms.

File System

In computer system, a File System defines how data or information is stored and retrieved from a storage disk. In Windows Operating System, the popular file systems are FAT32 and NTFS. On the other hand in Linux Operating System, the popular file systems are ext2, ext3, ext4, xfs (current), vfat, swap, ZFS and GlusterFS.

Partition Table

Partition can be considered as a piece of disk space. A partition table is a partition of a disk that contains information about sizes and locations of partitions on hard disk and it is located at the first sector of the disk. The two most popular partition tables are MBR and GPT.

Master Boot Record (MBR)

The MBR holds the information about how the logical partitions that contains file systems are organized on the disk. It also contains executable code (referred to as a boot loader) to function as a loader for the installed operating system. In Linux Operating System the MBR can have maximum 15 partitions and among them 4 partitions are primary and the rest are logical partitions. On the other hand in the Windows Operating System, the MBR can have maximum 24 partitions where 4 are primary and the rest are logical. The MBR uses 32 bit for storing block address and for hard disks with 512-byte sectors, the MBR can handle maximum 2TB (2³² × 512 bytes) hard disk.

GUID Partition Table (GPT)

As we can see MBR has limitation on both partitions (4 primary partitions) and storage capacity (2TB), a new partition table named GPT (Globally Unique Identifiers Partition Table) has been introduced (a part of the Unified Extensible Firmware Interface (UEFI) ) that can have 128 partitions. The GPT uses 64 bit for logical block address and for disks with 512-byte sectors, maximum size is 9.4 ZB (9.4 × 10²¹ bytes) or 8 ZiB.

How Disks Are Found in CentOS 7

In CentOS 7, the device files are located in /dev directory. SATA, SCSI and USB disks are shown as sda, sdb or  sdc (according to the number of disk) where sd represents SCSI DISK. For example, if you have a SATA or SCSI disk and install CentOS there, your disk drive will be shown as sda. As minimum automatic partition for CentOS 7 is 3, after installing CentOS 7 your sda disk partition will be labeld as sda1, sda2 and sda2. You can see your disk partition with the following commands.

Now if you add another raw SATA or SCSI HDD, the disk will be labeled as sdb. If you run the above command, you will find the new disk label as below.

Now if you add a USB flash drive, the disk will be labeled as the next available character but a partition will also be labeled like the below command output.

On the other hand your attached CD or DVD ROM will be found as cdrom or dvdrom or sr0 in dev directory.

The fdisk Tool to Manage CentOS 7 Partition

The fdisk is a command line utility that is used to manage partition in CentOS 7. You can find details about the fdisk tool with the man utility. In this article, we will know how to create a new partition and how to delete a partition with fdisk utility.

Note: The fdisk tool does not understand GUID partition table (GPT) and it is not designed for large partition (more than 2TB). In this case, the parted tool that supports multiple partition table formats (including MS-DOS and GPT) as well as large file size (more than 2TB) has to use.

To show available disk devices and partitions in your CentOS Linux, issue the fdisk command with –l option.

From the above output we can see there are three disk drives (sda, sdb and sdc) and their present status is like the below description.

• /dev/sda: It is the first SATA/SCSI disk where CentOS 7 is installed and has three partitions. /dev/sda1 is using as /boot partion, /dev/sda2 is swap partition and /dev/sda3 is the root partition.
• /dev/sdb:It is a raw SATA/SCSI disk drive.
• /dev/sdc: It is a USB flash drive and has a partition /dev/sdc1 and its partition is informing that it is a NTFS formatted disk. Linux normally cannot handle NTFS drive unlike FAT32. To play with NTFS drive in CentOS, you have to use NTFS3G utility.

Linux Partition ID

The partition ID in a partition’s entry in the partition table inside a master boot record (MBR) is a byte value intended to specify the file system the partition contains and/or to flag special access methods used to access these partitions. The following table shows the common Linux file system and their partition ID.

How to Create a New Partition with fdisk Tool in CentOS 7

We will now create a new partition with fdisk tool. To create a new partition, there must be free sectors/free space in a disk otherwise we cannot create a new partition there. At the time of CentOS 7 installation we used the entire available sectors/spaces in sda disk for three partitions. So, we cannot do any partition in sda drive. On the other hand, we can see sdb is a raw disk added later. So we will now be able to create a new partition here. Issue the following command to start creating a new disk partition in sdb drive.

Now fdisk command is waiting for further instruction. To get available instructions you can type m and hit enter, then it will show available instructions with description.

So to create a new partition, we have to type n and hit Enter key.

Now it will ask to choose partition type. As we are using MBR partition table, we can do only 4 primary partitions and others are extended partitions on a primary partition. We will create two partitions (one partition for data and other for backup) in sdb drive. As we are creating first partition, type p and hit Enter key.

Now it asks for partition number. Type 1 and hit Enter key.

It will now ask for entering first sector. Press Enter key to choose default

It will now ask for choosing last sectors or size. The size should start with PLUS SIGN and the unit will be (K=KiloByte, M=MegaByte and G=GigaByte). Put your desired value (I am giving 500MB) and hit Knter key.

So, 500MB partition has been created. To see created partition, type p and hit Enter.

To save this created partition type, w and hit Enter key.

Now if you see disk list, you will find sdb1 is now created.

Similarly, you can create another partition. I am creating another partition named sdb2 following the below command.

Now we have two newly created partitions. After creating partition, it is now required to inform the operating system to update partition table. Issue the following command to update partition table permanently.

Our partition table now has been updated. Now it is required to format our partition to use. The recent Linux supported file format system is xfs. So, issue the following commands to format sdb1 partition with xfs.

Similarly, format the sdb2 partition to xfs with the following command.

We have successfully formatted our newly created partition with xfs file system. Now these partitions are ready to keep data. But before keeping data, we have to mount partition to folder or directory. For practice, we will mound sdb1 to data directory and sdb2 to backup directory. So, first create these folders with the following command.

Now mount data to sdb1 and backup to sdb2 with the following command.

Browsing these folders, you can keep any data now. You can see usage of disk with the following command.

At this stage, our mounted partitions are temporary. If our Operating System gets restarted, these mounted directory will be lost. So, we need to do permanent mount. To do permanent mount, we have to put entry in fstab file. You can see current fstab entry with the following command.

You can see our new partitions are not present here. So, we have to put our new partition entry here. You can also see, to put entry we have to know UUID and type of any partitions. We can know UUID and file system with the following command.

Knowing UUID and file system, we are now ready to put entry in fstab file. The fstab file has the following format.

[Device] [Mount Point] [File System Type] [Options] [Dump] [Pass]

To mount all file systems in fstab file, issue the following command. It also show you if any error is occurred in fstab file.

New partition creation with permanent mounting using fdisk utility has been completed. Now we will show how to delete any partition in CentOS Linux if required.

How to Delete Linux Partition with fdisk Tool

Sometimes we may require deleting any partition. Using fdisk tool, we can easily delete any partition at any time. But before deleting any partition, you have to unmount the partition and remove fastab entry. Say, we want to remove sdb2 partition. So, first remove fstab entry by opening with vim editor.

Now unmounts the backup directory mounted to sdb2 partition with the following command.

We are now ready delete partition sdb2 because we have removed the fstab entry and also unmounted the backup directory from sdb2 partition. Now issue the following command to delete the sdb2 partition.

Type ‘d’ for deleting any partition.  It will also ask for partition number. Type ‘2’ because we want to delete sdb2 partiton.

You will find sdb2 partition has been deleted. To confirm deletion, type ‘p’ and then type ‘w’.

Now run partprobe command to update partition table.

Now if you see disk list with fdisk command, you will find the sdb2 partition is no more there.

With the above steps we have learnt how to delete a Linux partition with fdisk utility. We will now know how to mount a USB flash drive.

How to Mount USB Flash Drive (Pen drive) in CentOS 7

As I said before, the attached USB Flash Drive will show as the next available SD drive with an automatic created partition number. With the fdisk tool we can see the USB Flash Drive’s partition.

From the above output, we can see that a USB Flash Drive (sdc with partition /dev/sdc1) is attached. If the USB drive is formatted with the Linux File System described above, we can attached the partition with a directory and can list files, copy and paste any file or delete any file from there. But if the USB Flash Drive is formatted with NTFS, we have to use NTFS3G (a third party application) that will be discussed in my future article.

As we can see the attached USB Flash Drive is a FAT32 formatted drive, we will be able to mount the partition and can do copy, paste, delete or any other file operation. The following command will show how to mount a Linux file system supported USB Flash Drive in your CentOS 7 Operating System.

We have mounted the USB Flash Drive in automated created /mnt directory. Now we can browse the /mnt directory and can list or do any file operation there.

After using USB Flash Drive or Pendrive, we have to unmount the mounted directory and can safely remove the removable device.

You will find no file is there. That means, the mounted disk is now uncounted and we can safely remove the USB device.

Note: If you use a new USB Flash Drive or a file system that is not supported by the Linux, you have to format the USB device partition with the supported file system (ext2, ext3, ext4, xfs and so on) by the mkfs tool and mount the device in a directory or folder and then use the USB device browsing that directory or folder.

How to Mount CD/DVD in CentOS 7

As I said before, CD or DVD device is found in /dev/sr0 location. So to access CD or DVD media, we have to mount this location in a directory or folder. In the following example, we will mount CD or DVD location in automatic created directory media and browse media directory to get files in CD or DVD ROM.

After mounting CD/DVD to media directory, we are now can see the files in the CD or DVD media. We can do file operations here now.  If we do not want to use CD or DVD, we have to go out from media directory and then unmount the media directory from /dev/sr0 location. The following example will show how to unmount media directory from CD or DVD ROM.

The CD or DVD ROM is no more mounted to media directory. So, no files are found in the media forder now.

If you face any confusion to follow above steps properly, watch the below video about how to manage Linux partition with fdisk tool. I hope it will reduce your confusion.

How to manage CentOS 7 partition with fdisk tool has been discussed in this article. I hope you are now be able to manage your CentOS partition with fdisk tool if the partition table is MBR. But if you have GPT partition, you have to use parted tool (that you will be discussed in my future article) to manage partition in your CentOS Linux. However, if you face any confusion with fdisk tool, feel free to discuss in comment or contact with me from Contact page. I will try my best to stay with you.