103 lines
3.9 KiB
Markdown
103 lines
3.9 KiB
Markdown
---
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tags:
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- disks
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- computer-architecture
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- operating-systems
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---
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# Filesystems
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We cannot yet mount or interact with the partitions we have created. This is
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because we have not added a filesystem to each partition.
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> A filesytem is a form of [database](Basic_database_concepts.md); it
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> supplies the structure to transform a simple block device into the
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> sophisticated hierarchy of files and subdirectories that users can understand.
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Linux recognises many types of filesystems. The native Linux filesystem is the
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**ext4** (Fourth Extended Filesystem). Another common filesystem is **FAT**
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(File Allocation Table). Instances of this include _MSDOS_,_EXFAT_,_FAT-32_.
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They originate from Microsoft systems
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## Creating a filesystem
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Remember we have two partitions on our external drive: `sda1` and `sda2`. We are
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going to use the `mkfs` utility to create an EXT4 system on both.
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```bash
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mkfs -t ext4 /dev/sda1
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mkfs -t ext4 /dev/sda2
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```
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## Mounting a filesystem
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We can now mount our filesystems. When we mount, we must specify the following
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criteria with the request:
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- The name of the device we want to mount.
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- This will be the name or the partition. However the names (`sda` etc)
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assigned by the OS can change. In these cases and with GPT-based partitions
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you can use the UUID.
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- To see a list of devices and the corresponding filesystems and UUIDs on your
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system, you can use the **`blkid`** ('block id') program.
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```
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/dev/nvme0n1p3: UUID="c53577b5-92ef-4a0a-9a19-e488bfdfa39c" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="e152b9f4-7ce8-e74b-94db-2731c6fce53d"
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/dev/nvme0n1p1: UUID="9920-636A" BLOCK_SIZE="512" TYPE="vfat" PARTUUID="50592521-d386-194a-a362-bc8562ed6c82"
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/dev/nvme0n1p2: UUID="2ee6b834-0857-49dc-b8ba-a24d46d228ae" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="e08cc442-ef51-7b4f-9d55-e236c55c933c"
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/dev/sda2: UUID="abac6e2e-e3bf-40d3-a5ba-317c53eb27ce" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="4ef1b0e8-3d5b-c940-a3b1-0f85cddeca42"
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/dev/sda1: UUID="ba1e40c5-9b29-4309-a559-99bf8f68116f" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="b4983358-6036-df40-a1f8-793976f3dfb1"
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```
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- The filesystem type (optional)
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- The **mount point**
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- This is the place within the existing filesystem where you want to mount the
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partition.
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- When you mount to a directory, this directory _becomes_ the disk you have
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mounted, you will not see it as a subdirectory within the the mount point,
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you will just see the contents of the disk itself
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```bash
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mkdir mountpoint
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mount -t ext4 /dev/sda1 /mnt
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touch test.txt
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```
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Our `sda1` partition is now mounted at `mountpoint`. We can go ahead and create
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files. If we now look within the graphical file manager when we click on the
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`sda1` volume, we will see the new file we have created in `mountpoint`.
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## fstab
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In most cases you want your filesystem to mount automatically on boot and always
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to the same mount point. You can do this via the specialised `fstab` file on
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Linux systems within the `/etc/` directory.
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This is my current `fstab`:
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```
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# <file system> <dir> <type> <options> <dump> <pass>
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# /dev/nvme0n1p2
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UUID=2ee6b834-0857-49dc-b8ba-a24d46d228ae / ext4 rw,relatime 0 1
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# /dev/nvme0n1p3
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UUID=c53577b5-92ef-4a0a-9a19-e488bfdfa39c /home ext4 rw,relatime 0 2
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/swapfile none swap sw 0 0
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```
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It shows my root and home filesystems and my
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[swap](Swap_space.md) file. Note that we use the UUID
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to name the partition rather than its name in `/dev/`. The order of the
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parameters is as follows:
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- Device name or UUID
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- The mount point
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- The filesystem type (in the example there are two types (`ext4` and `swap`))
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- Options
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- Now largely irrelevant backup information, set to )
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- Filesystem integrity test order
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- Runs the `fsck` ('filesystem check') command against each filesystem
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- Put `1` against the root partition for this to be checked first
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- Put `0` for no checks to take place
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