Linux 101 : An overview of the Linux filesystem (mkfs, mkswap, fstab, lsblk, df,...).
To be able to use a partition, Linux needs to have a filesystem on it.
Linux supports a number of filesystems ext2, ext3 and ext4 for example.
It supports other filesystems like the below:
- ReiserFS
- JFS
- ZFS
Creating a filesystem:
The filesystem manages the data on the disk.
To create a filesystem on a partition, we use:
Example:
We could also use mkfs.ext3 to create an ext3 filesystem on /dev/sda1 partition:
To display the list of commands that create different types of filesystems (ext2,ext3,...), we use:
Mounting partitions:
To be able to use the filesystem created on a partition we need to mount it on a mountpoint :
The mount_point is a directory to which we attach a partition, it provides an entry point to the filesystem that lives on that partition.
Example:
The "/mnt" directory has to exist on the system.
To list all the physical and virtual filesystems on a system
, we use:
Displaying partitions and their used space:
We can use the below command to check all the partitions and its used space:
Persisting between reboots (mounted partitions):
To persist between reboots, we add the partition we need to mount in the "/etc/fstab" file.
Mount optionsin the "/etc/fstab" file:
- auto: the partition will be mounted automatically
- noauto:the partition will not be mounted automatically
- user: permits any user to mount the filesystem
- noexec: prevents the execution of programs on the filesystem
Pass:
0: the kernel doesn't check the partition.
1: the partition is checked first by the kernel.
2: partition is checked after the one partition"tagged" with "1" i checked.
1: the partition is checked first by the kernel.
2: partition is checked after the one partition"tagged" with "1" i checked.
Dump:
0 : the file system is not backed up by the dump utility
1 : file system is backed up by the dump utility.
1 : file system is backed up by the dump utility.
Listing of the disks UUIDs:
A UUID is an identifier Linux uses to "tag" disk partitions. We can use the below command to display all the UUIDs on a system:
Partition labels:
To add a label to a partition (like the with "opt" tag in the "fstab" file above), we use for example:
"/dev/sda1" is the device and "opt" is its label.
Unmounting a mounted device:
To unmount a device, we use:
We could also use the below command:
Remark:
If a user or a process is using a file on that partition, we will not be able to unmount it, and we will receive "device busy" message.
A swap partition is a regular disk partition that the system will use as a substitute for the "RAM" when the "RAM" on the system is full.
We can create a swap partition using the partition "sdb2" for example, using the below command:
To enable the swap partition, we use:
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