File systems and mount points
You're missing out on a very important way Ubuntu/Linux handles file systems: all comes down to the same root (/
) and other file systems ("volumes", "disks", "partitions") will be mounted on a location inside the root.
To explain two most interesting lines:
Your /
is full:
/dev/mapper/eubuntu10x32-root 3.5G 3.3G 0 100% /
Here you see a "device mapper" meta-device being used for your root filesystem. I think you're using LVM here or encryption.
3.5GiB for a /
is a very low capacity for a desktop installation, unless you have directories like /usr
, /var
moved out of it. In your case it's clearly not sufficient.
Your second disk (sdb
, without partitions) is mounted at /home
and a partition of sda
is mounted as /boot
:
/dev/sdb 50G 27G 21G 57% /home
/dev/sda1 228M 35M 181M 17% /boot
This separated /boot
is common for a LVM/encrypted installation to allow the bootloader (Grub) to load the relevant software/drivers to be able to reach your other file systems to actually boot the operating system.
So, basically, your /home
and /boot
aren't just directories. They are directories on the /
file system, but there's another file system mounted on top of it. This means that whenever you descend into it, you're looking into a different file system. Each file system has its own capacity, listed by df
.
While you moved out /home
and /boot
, this wasn't enough to have sufficient space available on /
. Solutions: grow the /
file system, move out more like /usr
or /var
to another file system.
Are all directories under /
mount points?
Directories not being a mount point are actual regular directories part of file system in mounted as /
. There are also special ones, which don't actually represent data on disks, but in UNIX/Linux, everything is represented as files such as sockets, kernel interfaces (/proc
, /sys
), etc. and even directories itself are files.
How does this compare to Windows?
Windows tends to hide the difference between the devices/partitions and the actual file system being mounted. This means that a C:
"drive" can also be mounted as such. In Ubuntu/Linux, you'll see that a partition, e.g. /dev/sda1
(first partition on sda
) can be mounted (content being made available to the user) to any location. There's no second root for this like Windows makes the second drive a D:
.