How to create a filesystem on a Linux partition or logical volume
======
Learn to create a filesystem and mount it persistently or
non-persistently in your system.
![Filing papers and documents][1]
In computing, a filesystem controls how data is stored and retrieved and helps organize the files on the storage media. Without a filesystem, information in storage would be one large block of data, and you couldn't tell where one piece of information stopped and the next began. A filesystem helps manage all of this by providing names to files that store data and maintaining a table of files and directories—along with their start/end location, total size, etc.—on disks within the filesystem.
In Linux, when you create a hard disk partition or a logical volume, the next step is usually to create a filesystem by formatting the partition or logical volume. This how-to assumes you know how to create a partition or a logical volume, and you just want to format it to contain a filesystem and mount it.
### Create a filesystem
Imagine you just added a new disk to your system and created a partition named **/dev/sda1** on it.
1. To verify that the Linux kernel can see the partition, you can **cat** out **/proc/partitions** like this:
```
[root@localhost ~]# cat /proc/partitions
major minor #blocks name
253 0 10485760 vda
253 1 8192000 vda1
11 0 1048575 sr0
11 1 374 sr1
8 0 10485760 sda
8 1 10484736 sda1
252 0 3145728 dm-0
252 1 2097152 dm-1
252 2 1048576 dm-2
8 16 1048576 sdb
```
2. Decide what kind of filesystem you want to create, such as ext4, XFS, or anything else. Here are a few options:
3. For the purposes of this exercise, choose ext4. (I like ext4 because it allows you to shrink the filesystem if you need to, a thing that isn't as straightforward with XFS.) Here's how it can be done (the output may differ based on device name/sizes):
```
[root@localhost ~]# mkfs.ext4 /dev/sda1
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=8191 blocks
194688 inodes, 778241 blocks
38912 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=799014912
24 block groups
32768 blocks per group, 32768 fragments per group
8112 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Allocating group tables: done
Writing inode tables: done
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done
```
4. In the previous step, if you want to create a different kind of filesystem, use a different **mkfs** command variation.
### Mount a filesystem
After you create your filesystem, you can mount it in your operating system.
1. First, identify the UUID of your new filesystem. Issue the **blkid** command to list all known block storage devices and look for **sda1** in the output:
The **df -h** command shows which filesystem is mounted on which mount point. Look for **/dev/sd1**. The mount command above used the device name **/dev/sda1**. Substitute it with the UUID identified in the **blkid** command. Also, note that a new directory was created to mount **/dev/sda1** under **/mnt**.
3. A problem with using the mount command directly on the command line (as in the previous step) is that the mount won't persist across reboots. To mount the filesystem persistently, edit the **/etc/fstab** file to include your mount information:
4. After you edit **/etc/fstab** , you can **umount /mnt/mount_point_for_dev_sda1** and run the command **mount -a** to mount everything listed in **/etc/fstab**. If everything went right, you can still list **df -h** and see your filesystem mounted:
