Getting file system free space

Question

This isn't a problem as such, more a request for information based on ignorance of the Linux filesystem. The very short question is:

How do I find out how much free and used space there is on the volume from which Ubuntu is running?

More detail:

I'm running Ubuntu 12.04 from a 64Gb USB3 stick, created from booting up a year-old Ubuntu 12.04 DVD and running Startup Disk Creator. The reason for this is that the Master Boot Record on my hard disk, holding Windows 7, has gone belly-up, and whilst awaiting a recovery disk I'm running Ubuntu off USB or DVD as a 'trial'. (And will continue to run Ubuntu after restoring Windows, as I've rediscovered my love of the penguin :o))

After installing Ubuntu on the stick I ran the software update app, which downloaded some 450Mb of updates and took a couple of hours to install to the stick. A couple of times I got a message saying that disk space was short. So I looked in the file manager (or whatever it's called these days) and couldn't see the stick listed, just:

• SYSTEM
• hard disk (listed as 479Gb Filesystem)
• two other partitions that had been created by Windows
• "4.3GB Filesystem" which when I try to open gives the error "Could not find /cow", and when I try to unmount it tells me I can't because it's not mounted - D'OH!!

Edit: screenshot of file manager

Edit: screenshot of low disk space warning

What I can't see is the USB stick from which I'm running Ubuntu. Where's it gone, anybody know?

This is tangentially related to a previous question of mine about system tools, in that I'm trying to get control and knowledge of the system in the newest incarnation of Ubuntu.

Answer 1

There are a few tools I use when in this situation: df, du, and mount

du is the most useful for hunting down the culprit that filled up your filesystem:

$du -h --max-depth=1

However at the filesystem root, /, you won't have permission to access all of the directories to get a read on file sizes, so you'll need sudo to get full privileges. I just did this on our server at / and our raid is kinda big, so I bailed on that.

Examples follow:

15:08 chris@server /$ sudo du -h --max-depth=1
8.0K    ./mnt
16K     ./build
4.1G    ./opt
4.0K    ./backup
12K     ./media
13M     ./lib32
38M     ./root
300K    ./dev
6.0M    ./sbin
2.4G    ./lib
2.9G    ./var
4.0K    ./selinux
50M     ./home
2.3G    ./usr
0       ./proc
7.9M    ./bin
5.9M    ./tmp
200K    ./srv
4.0K    ./run
0       ./sys
4.0K    ./cdrom

I hit ctrl+c because I'm done waiting on /raid... So let's see what df says:

15:14 chris@server /$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sdb7              92G  9.0G   79G  11% /
none                  1.9G  300K  1.9G   1% /dev
none                  1.9G     0  1.9G   0% /dev/shm
none                  1.9G  7.3M  1.9G   1% /var/run
none                  1.9G     0  1.9G   0% /var/lock
none                  1.9G     0  1.9G   0% /lib/init/rw
/dev/sda1             3.6T  2.3T  1.2T  66% /raid
/dev/sdb9             276M   88M  175M  34% /boot
/dev/sdb8              88G  3.1G   81G   4% /var

Oh, wow, the raid is two-thirds full, maybe it's worth the wait to figure it out?

15:15 chris@server /raid$ !du
du -h --max-depth=1
852M    ./www
20K     ./investedin
9.8M    ./ups
99M     ./dealers
3.0G    ./photoshoot
69M     ./catalog_tech
86G     ./misc
4.9G    ./marketing
16G     ./pics
193G    ./Video
37G     ./mechanical_design
14M     ./tmp
16K     ./lost+found
93G     ./programs
16K     ./.Trash-1000
17G     ./Products
1.3G    ./vendors
1.1G    ./docs
128K    ./.Trash-1001
20M     ./customers
2.9M    ./po_invoices
18M     ./_SCANS

Well, it's still hanging out churning, so I'll be patient and let it go in the background. To analyze the above, I look through the sizes of the directories for who the disk hog is. Notice ./programs is 93G. If that's unexpected, you start drilling down that tree.

I prefer du -h --max-depth=1 because with any more depth, you get a ton of output and in this case, you might just need that one directory where a log has gone crazy (like on a website?)

Edited to add:
And mount isn't always applicable for your exact case, however, I have used Linux and the above techniques to rescue a Windows install with no free space. mount can help you see what hard drives are mounted where. Also notice how df also hints at the output from mount.

15:25 chris@server ~$ mount
/dev/sdb7 on / type ext4 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
none on /sys type sysfs (rw,noexec,nosuid,nodev)
none on /sys/fs/fuse/connections type fusectl (rw)
none on /sys/kernel/debug type debugfs (rw)
none on /sys/kernel/security type securityfs (rw)
none on /dev type devtmpfs (rw,mode=0755)
none on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
none on /dev/shm type tmpfs (rw,nosuid,nodev)
none on /var/run type tmpfs (rw,nosuid,mode=0755)
none on /var/lock type tmpfs (rw,noexec,nosuid,nodev)
none on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
/dev/sda1 on /raid type ext4 (rw)
/dev/sdb9 on /boot type ext4 (rw)
/dev/sdb8 on /var type ext4 (rw)

What the above tells us is that the first hard drive's first partition (a hardware RAID 5) is on /raid and the actual "hard drive" in the computer is sdb. With / on sdb7, that reminds me this is the 2nd or 3rd OS I've had on this disk on this server. I put /var on a separate partition for when logs go crazy.