Understanding devices on Linux systems

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        14G  6.7G  6.2G  52% /
devtmpfs        4.0M     0  4.0M   0% /dev
tmpfs           886M   96K  886M   1% /dev/shm
efivarfs         64K  6.0K   53K  11% /sys/firmware/efi/efivars
tmpfs           355M  1.7M  353M   1% /run
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-journald.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-network-generator.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-udev-load-credentials.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-tmpfiles-setup-dev-early.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-sysctl.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-tmpfiles-setup-dev.service
tmpfs           886M   16K  886M   1% /tmp
/dev/sda3        14G  6.7G  6.2G  52% /home
/dev/sda2       974M  358M  549M  40% /boot
/dev/sda1       599M   20M  580M   4% /boot/efi
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-tmpfiles-setup.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-resolved.service
tmpfs           1.0M     0  1.0M   0% /run/credentials/systemd-vconsole-setup.service
tmpfs           178M  180K  177M   1% /run/user/1000
tmpfs           178M   76K  177M   1% /run/user/1001

You can reduce the output to a more concise listing like this (removing the tmpfs file systems):

$ df -h | grep -v tmpfs
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        14G  6.7G  6.2G  52% /
efivarfs         64K  6.0K   53K  11% /sys/firmware/efi/efivars
/dev/sda3        14G  6.7G  6.2G  52% /home
/dev/sda2       974M  358M  549M  40% /boot
/dev/sda1       599M   20M  580M   4% /boot/efi

You can have the df command supply information on one partition with a command like this:

$ df -h /home
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda3        14G  6.7G  6.2G  52% /home

Using the mount command without arguments will display all of the mounted file systems. To list file systems by type, you can use a command like this that lists only ext4 file systems:

$ mount -t ext4
/dev/sda2 on /boot type ext4 (rw,relatime,seclabel)

Passing the output of the mount command to the column command will provide a listing that will likely be easier to read as the output will be displayed with separated columns of data.

$ mount | column -t

The fdisk -l command will display details on file systems, but requires root access.

$ sudo fdisk -l
Disk /dev/sda: 14.91 GiB, 16013942784 bytes, 31277232 sectors
Disk model: KINGSTON SNS4151
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 9645D103-5519-4B2A-82FB-636FED806E1B
Device       Start      End  Sectors  Size Type
/dev/sda1     2048  1230847  1228800  600M EFI System
/dev/sda2  1230848  3327999  2097152    1G Linux extended boot
/dev/sda3  3328000 31277055 27949056 13.3G Linux filesystem
Disk /dev/zram0: 1.73 GiB, 1855979520 bytes, 453120 sectors
Units: sectors of 1 * 4096 = 4096 bytes
Sector size (logical/physical): 4096 bytes / 4096 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

The lspci command will display information on pci (peripheral component interconnect) devices.