Find the Largest Files on a Linux Machine

The PBX in a Flash machine at a client site sends me a daily Logwatch email (setup described here). At the bottom of that email are a few lines telling me how much disk space is in use. I also SNMP to monitor disk usage (described here).

Both of these tell me that disk usage is up to 75%. Looking back a few months, it was only 50%. What is using up so much space?

A quick Google search turned up this article:  How Do I Find The Largest Top 10 Files and Directories On a Linux / UNIX / BSD? The very first command:

$ du -a /var | sort -n -r | head -n 10

showed me what I need to know:

11288832        /var
10821596        /var/spool
10821208        /var/spool/asterisk
10818532        /var/spool/asterisk/backup
10765244        /var/spool/asterisk/backup/Daily_00_30
149624  /var/lib
145476  /var/log
125308  /var/log/asterisk
123680  /var/log/asterisk/freepbx_dbug
88964   /var/www

A quick check of the /var/spool/asterisk/backup/Daily_00_30 directory confirms that my old daily backups are not being deleted. So it’s back to Linux Daily Delete Job with Logwatch to figure out what isn’t working.

Note If you want to see the whole file system (including mount points etc.), remove “var” from the command:

$ du -a / | sort -n -r | head -n 10

Update May 11, 2019

The above commands require GNU/sort. Searching more specifically for Ubuntu options, I came across this ServerFault answer suggesting ncdu. After a quick install

sudo apt install ncdu

I was quickly able to list the top system hogs with

sudo ncdu /

The simple GUI, running in Putty, let me drill down to /opt/bitnami/apps and explore which folders and files are biggest.

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