Filesystem – method of efficient data storing on Linux systems. Linux is using filesystems to manage stored data on storage devices. A filesystem maintains a map to locate each file placed in the storage device. If we take a look at Windows and the way of storing data there, you will find that paths are indicating on which drive specific data is stored. However, Linux uses different way to map data locations on a drive. It uses virtual directory structure, which contains file paths from all storage devices installed on the system – merged into one single directory structure. Show
Virtual directory – this directory structure contains single base directory called root directory (denoted with / sign). Also, Linux places physical devices (HDDs and SSDs for example) in virtual directory using mounting points. A mount point is a directory placeholder within the virtual directory that points to a specific device.  Here are the most important directories inside one Linux filesystem: /bootContains boot loader files used to boot the system/etcContains system and application configuration files/homeContains user data files/mediaUsed as mount point for removable devices/mntUsed as mount point for removable devices, too/optContains data for optional third-party applications/tmpContains temporary files created by system users/usrContains data for standard Linux programs/usr/binContains local user programs/usr/localContains data for programs unique to the installation/usr/sbinContains data for system programs and data/varContains variable data files, including system and application logsCommon Filesystem TypesBefore assigning drive partition to a mount point in virtual directory, filesystem must be formatted. Each filesystem has its own way of indexing files and directories and tracking file access. All these are similar, but different. First, let’s discuss types of filesystem Linux supports (both Linux filesystems and non-Linux filesystems). Then, we will see how to create filesystem, then mount it, and then manage and administer them. Here are Linux Filesystem types we can use: btrfsSupports files up to 18000 petabytes (just insane).Performs RAID and LVM, built-in snapshots for backup, improved fault-tolerance, data compression on the flyecryptfsApplies POSIX compliant encryption protocol to data before storing it on the device. Only operating system that created that data, can read it.ext3Supports files up to 2 terabytes. Total filesystem size can reach 17 terabytes. Supports journaling, faster startup and recoveryext4Supports files up to 17 terabytes. Total filesystem size can reach 144 petabytes. Supports journaling, improved performanceswapNot indended for storing persistent data. Swap filesystem creates virtual memory using space on physical drive. 2GB swap space acts as 2GB RAM system can use. However, it is stored in physical drive, not in RAM memory. Those were Linux filesystems, and now let’s see which non-Linux filesystems are supported by Linux: CIFSFilesystem protocol created by Microsoft. Used to read and write data across a network using network storage device.exFATCommonly used to format USB devices and SD cardsHFSDeveloped by Apple for Mac systems. Linux can interact with HFS and with HFS+ filesystemsISO-9660Weird name. It is standard used to create filesystems on CD-ROM devicesNFSStandard for reading and writing data across a network using network storage deviceNTFSFilesystem used by Microsoft. Linux can read and write data on NTFS partitionsSMBFilesystem created by Microsoft. Used for network storage and interacting with other network devices (such as printers).Support for SMB allows Linux clients and servers to interact with Microsoft clients and servers on a networkUDFUsed on DVD-ROM devices to store data. Linux can read data from DVD, and write data to DVD, using this filesystemVFATExtension for Microsoft’s FAT filesystem. Often used for removable devices such as USB memory sticksZFSCreated by Sun Microsystems for Unix workstations and servers. Has features similar to btrfs Linux filesystem Creating filesystemsProgram to create filesystem is called mkfs. Actually, there are multiple programs, such as mkfs.ext4, to create ext4 filesystem. But, instead of learning all individual program names, use mkfs and use -t option where you will specify filesystem type. Before using mkfs command, be careful to specify right partition or device. If you make mistake, you will format wrong partition or disk, loosing all data in it.To create swap filesystem, use mkswap command. After we formatted drive partition with a filesystem, add filesystem to the virtual directory on your Linux system. This process is called mounting the filesystem. This can be done manually from command line, or automatically let Linux do it after boot: 1. Manually mounting devices to a filesystem:This will temporary mount filesystem to Linux virtual directory. We will use mount command. We called mount command, specified filesystem type with –f flag, chose ext4 as our filesystem, and mounted /dev/sdb1 to /media/usb1 Downside for mount command is that temporarily mounts the device on virtual directory. When you reboot system, you must mount the device again. This method is good for removable devices. To unmount the device, use umount command. 2. Automatically mount devices to a filesystem:For permanent storage devices, Linux uses /etc/fstab file. Inside this file, there are paths to devices which are automatically mounted at boot time. Let’s take a look what is inside Aight, looks a bit messy, but let’s dissect this into little pieces:
Devices are identified with their UUID value, ensuring correct drive partition is mounted. The first partition here is mounted on /boot directory, it uses vfat filesystem type. The second partition is mounted on root / of the virtual directory, it uses ext4 filesystem type. The third partition is mounted at /home and it uses ext4 filesystem type too. If you want to mount something automatically, add it in /etc/fstab file. Managing FilesystemsTools to manage filesystem are used to monitor disk performance, disk usage, partition sizes, mount points, etc. These are the most used tools for this: Managing with df commandThe df command displays disk usage by partition. Let’s take a look what my machine pulls out. With –h argument, it prints human-readable output using megabytes, gigabytes… As you can see, I have few directories that take space on a partition. The most important ones are /dev/sda[123] which are real partitions on my SSD. The df command shows total size of each partition, used and available space, and where is mounted on a filesystem. Managing filesystem with duDisplays disk usage by directory. Use –h flag to see output in human-readable form. Let’s take a look how it looks like: Managing filesystems with iostatDisplays real-time chart of disk statistics by partition. Install it with sysstat package. The iostat command is used to monitor system input/output device loading and it is very versatile. Here’s an example of iostat output: The iostat will generate CPU utilization report, Device utilization report, and network filesystem report. Let’s take a look at “CPU utilization report”: Device utilization report is showing following output. This block of text shows statistics for physical device or partition. Let’s examine each column: Managing filesystems with lsblkDisplays current partition sizes and mount points on all block devices. The command will show all block devices (except RAM) in a tree-like format. Here are the most used flags for lsblk: aPrint empty devicesbPrint SIZE in bytes, not in human-readable formatdDon’t print device holders or partitions. Just print devicefPrint information about filesystemsiUse ASCII characters to create a treemShow device owner, group and file permissions informationnNo header line shownAnd here is quick little example of lsblk command. The -n flag will not show header line, the -m flag shows device owner, group, and file permissions, and the -i flag uses ASCII to create that little tree-like structure for /dev/sda/ partitions Which command is used to add a new external filesystem to the existing filesystem in Linux?The mkfs command makes file systems. On other operating systems, creating a file system is called formatting.
What is file system command in Linux?What is the Linux File System? Linux file system is generally a built-in layer of a Linux operating system used to handle the data management of the storage. It helps to arrange the file on the disk storage. It manages the file name, file size, creation date, and much more information about a file.
What is virtual directory in Linux?A virtual directory is a path or alias within a website that refers users to another directory where the actual data is hosted. The referred directory can be a physical directory on a local server's hard drive or a directory on another server (network share).
Which command is used to mount file system read only?Read-only mode mount is invoked by using the mmmount command with the -o ro flags. After a read-only mode mount is done, some data may be sufficiently accessible to allow copying to another file system.
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