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FedKad
Asked: 2020-05-02 05:01:04 +0800 CST

Prevent du command report inflated info about /snap directories

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I have an Ubuntu 20.04 server installed on a single 8GB drive. The default installation has some "snap"s installed also. So, there are some "squashfs" file systems also reported by the df command:

# df -mT
Filesystem     Type     1M-blocks  Used Available Use% Mounted on
/dev/root      ext4          7877  1837      6025  24% /
devtmpfs       devtmpfs       465     0       465   0% /dev
tmpfs          tmpfs          477     0       477   0% /dev/shm
tmpfs          tmpfs           96     1        95   1% /run
tmpfs          tmpfs            5     0         5   0% /run/lock
tmpfs          tmpfs          477     0       477   0% /sys/fs/cgroup
/dev/loop0     squashfs        18    18         0 100% /snap/amazon-ssm-agent/1566
/dev/loop1     squashfs        94    94         0 100% /snap/core/9066
/dev/loop2     squashfs        55    55         0 100% /snap/core18/1705
/dev/loop3     squashfs        69    69         0 100% /snap/lxd/14804
/dev/loop4     squashfs        70    70         0 100% /snap/lxd/14890
/dev/loop5     squashfs        55    55         0 100% /snap/core18/1754
tmpfs          tmpfs           96     0        96   0% /run/user/1000

As you see, there is only 1837MB of data stored in the (only) disk.

Now, I am trying the list that disk usage for each directory present under root (/) using the following command:

# du -smc /* 2>/dev/null
0   /bin
48  /boot
0   /dev
8   /etc
1   /home
0   /lib
0   /lib32
0   /lib64
0   /libx32
1   /lost+found
1   /media
1   /mnt
1   /opt
0   /proc
1   /root
1   /run
0   /sbin
1116    /snap
1   /srv
0   /sys
1   /tmp
1166    /usr
601 /var
2938    total

The output shows a large amount of disk space used by the /snap directory, which of course is not true.

What is the correct way to count the size of files residing only on "real disk" filesystems? Adding the option -x to du does not make me feel comfortable, because in the future I may have another "real disk" filesystem mounted under /home for example and I do want that to be counted in du's output.

disk snap squashfs df du

2 Answers

  1. Unlike df, as far as I know du does not provide a --exclude-type to skip particular filesystem types. However you could exclude specific top level directories by glob pattern:

    du -smc --exclude=/snap /* 2>/dev/null

    or (to exclude ephemeral filesystems as well) and assuming your shell supports brace expansion:

    du -smc --exclude=/{proc,run,sys,snap} /* 2>/dev/null
    • 4

  2. You have to correctly use du's arguments. Something like:

    du --one-file-system -smc /* --exclude=/snap 2> /dev/null

    For reference use man du locally or online.

    • 3