# Devices, Partitions and Mounting

## Mounted Devices

* All the active storages devices in Linux are part of the single file system starting at **`/`**.

![](/files/b50kYfnc1ZQQXkWVGXPh)

![](/files/IaFyEJm9iPYI7rDiJcHu)

* The hard drive is identified by **`/dev/sda`**:
  * **s** identifier indicates that it is a sata drive
  * **a** indicates that it is the first drive (/dev/sdb would the the second drive if present)
  * the drive is divided into different volumes/partitions, each with its own ID mounted at a different location in the file system
    * First partition is **`/dev/sda1`**
    * Second partition is **`/dev/sda2`**, mounted at /boot/efi
    * Third partition is **`/dev/sda3`**, mounted at filesystem root **/**
  * Every file or directory that isn't in one of the subdirectory mount points, resides on the /dev/sda3 partition since it is at the filesystem root.

![](/files/1smH9WkYb0eMsmqDJM7b)

* The virtual dvd drive is identified by the read-only **`/dev/sr0`**

## Mounting Configuration

```bash
cat /etc/fstab
	# /etc/fstab: static file system information.
	#
	# Use 'blkid' to print the universally unique identifier for a
	# device; this may be used with UUID= as a more robust way to name devices
	# that works even if disks are added and removed. See fstab(5).
	#
	# <file system> <mount point>   <type>  <options>       <dump>  <pass>
	# / was on /dev/sda3 during installation
	UUID=2b17aaa3-594a-43eb-9c65-3b89ebb0bc05 /               ext4    errors=remount-ro 0       1
	# /boot/efi was on /dev/sda2 during installation
	UUID=4704-6965  /boot/efi       vfat    umask=0077      0       1
	/swapfile                                 none            swap    sw              0       0
```

* Each partition has a unique identifier **`UUID`** that the system uses.

### mount

* **`mount`** - command used to mount partitions, or shows the current mounted devices

```bash
mount
	sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
	proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
	udev on /dev type devtmpfs (rw,nosuid,relatime,size=1975416k,nr_inodes=493854,mode=755,inode64)
	devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
	tmpfs on /run type tmpfs (rw,nosuid,nodev,noexec,relatime,size=402020k,mode=755,inode64)
	/dev/sda3 on / type ext4 (rw,relatime,errors=remount-ro)
	securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
	tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,inode64)
	tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k,inode64)
	cgroup2 on /sys/fs/cgroup type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot)
	pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
	bpf on /sys/fs/bpf type bpf (rw,nosuid,nodev,noexec,relatime,mode=700)
	systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=29,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=15742)
	tracefs on /sys/kernel/tracing type tracefs (rw,nosuid,nodev,noexec,relatime)
	debugfs on /sys/kernel/debug type debugfs (rw,nosuid,nodev,noexec,relatime)
	mqueue on /dev/mqueue type mqueue (rw,nosuid,nodev,noexec,relatime)
	hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
	fusectl on /sys/fs/fuse/connections type fusectl (rw,nosuid,nodev,noexec,relatime)
	configfs on /sys/kernel/config type configfs (rw,nosuid,nodev,noexec,relatime)
	none on /run/credentials/systemd-sysusers.service type ramfs (ro,nosuid,nodev,noexec,relatime,mode=700)
	[...]
```

### df

* **`df`** - displays the disk file system space usage of all the mounted partitions

```bash
df -h
# Print sizes in a human-readable format
	Filesystem      Size  Used Avail Use% Mounted on
	tmpfs           393M  1,6M  392M   1% /run
	/dev/sda3        24G  8,6G   15G  38% /
	tmpfs           2,0G     0  2,0G   0% /dev/shm
	tmpfs           5,0M  4,0K  5,0M   1% /run/lock
	/dev/sda2       512M  5,3M  507M   2% /boot/efi
	tmpfs           393M  2,4M  391M   1% /run/user/1000
```

### du

* **`du`** - display the disk usage of given files or directories
* It can be combined with other commands with pipes.

```bash
du -sh ~
# Summarize the total disk usage of the directory and print in a human-readable format
	148M	/home/user
```

***


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://blog.syselement.com/tcm/courses/linux-101/3-filesystem/devices.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.