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I recently installed Ubuntu 18.04 on my machine and installed all the regular stuff that I had put the 17.10 version. However, it seems like something is amiss as my Linux partition is showing absurdly high memory used.

Here's what a df -h looks like (sda7 is Linux)

Filesystem      Size  Used Avail Use% Mounted on
udev            3.9G     0  3.9G   0% /dev
tmpfs           789M  1.9M  787M   1% /run
/dev/sda7       128G  116G  5.0G  96% /
tmpfs           3.9G   24M  3.9G   1% /dev/shm
tmpfs           5.0M  4.0K  5.0M   1% /run/lock
tmpfs           3.9G     0  3.9G   0% /sys/fs/cgroup
/dev/loop0       13M   13M     0 100% /snap/gnome-characters/69
/dev/loop4       87M   87M     0 100% /snap/core/4486
/dev/loop3       21M   21M     0 100% /snap/gnome-logs/25
/dev/loop6      141M  141M     0 100% /snap/gnome-3-26-1604/59
/dev/loop10      87M   87M     0 100% /snap/core/4571
/dev/loop9      3.8M  3.8M     0 100% /snap/gnome-system-monitor/39
/dev/loop8       87M   87M     0 100% /snap/core/4650
/dev/loop14     181M  181M     0 100% /snap/vlc/190
/dev/loop7       22M   22M     0 100% /snap/gnome-logs/31
/dev/loop12     2.4M  2.4M     0 100% /snap/gnome-calculator/167
/dev/loop11      13M   13M     0 100% /snap/gnome-characters/86
/dev/loop13     141M  141M     0 100% /snap/gnome-3-26-1604/62
/dev/loop2      3.4M  3.4M     0 100% /snap/gnome-system-monitor/36
/dev/loop5      1.7M  1.7M     0 100% /snap/gnome-calculator/154
/dev/loop1      140M  140M     0 100% /snap/gnome-3-26-1604/64
/dev/sda2       147G   57G   91G  39% /mnt/84AEB359AEB3430A
/dev/sda3       175G  106G   70G  61% /mnt/40945D4B945D4496
tmpfs           789M   16K  789M   1% /run/user/120
tmpfs           789M   68K  788M   1% /run/user/1000

Based on this link, I ran ncdu and it shows a rather modest (and what it should be) usage:

. 155.3 GiB [##########] /mnt                                                                                                          
   24.2 GiB [#         ] /usr
   20.9 GiB [#         ] /home
.   3.4 GiB [          ] /snap
.   2.1 GiB [          ] /var
    2.0 GiB [          ]  swapfile
  775.2 MiB [          ] /lib
  179.8 MiB [          ] /opt
  137.0 MiB [          ] /boot
.  14.2 MiB [          ] /etc
   12.3 MiB [          ] /bin
   11.3 MiB [          ] /sbin
.   1.8 MiB [          ] /run
. 212.0 KiB [          ] /tmp
!  16.0 KiB [          ] /lost+found
   12.0 KiB [          ] /media
    4.0 KiB [          ] /lib64
e   4.0 KiB [          ] /srv
!   4.0 KiB [          ] /root
e   4.0 KiB [          ] /cdrom
.   0.0   B [          ] /proc
.   0.0   B [          ] /sys
    0.0   B [          ] /dev
@   0.0   B [          ]  initrd.img.old
@   0.0   B [          ]  initrd.img
@   0.0   B [          ]  vmlinuz.old
@   0.0   B [          ]  vmlinuz

How come there is unaccounted disk usage?

Melebius
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Anshul
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    Run ncdu -x / as root – Ipor Sircer May 23 '18 at 10:39
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    You think that you have an external disk mounted on /mnt but you really don't? Or, at some point, didn't? What happens if you unmount sda2 and sda3 and try again to look at the disk space? – AlexP May 23 '18 at 10:42
  • What is the output of lsblk -f? – Mio Rin May 23 '18 at 13:29
  • @IporSircer That helped! Turns out, one of my LXCs has bloated up its syslog to a whopping 48 Gigs and was not being accounted for when not running ncdu as super user. Thanks! – Anshul May 24 '18 at 03:39

1 Answers1

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As suggested by Ipor in the comments to the question, running ncdu as non-root was not giving correct results. It was not accessing root-protected areas and as a result, not looking into some places.

Doing that revealed the problem and was rectified.

Anshul
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