Disk Input Plugin

The disk input plugin gathers metrics about disk usage.

Note that used_percent is calculated by doing used / (used + free), not used / total, which is how the unix df command does it. See https://en.wikipedia.org/wiki/Df_(Unix) for more details.

Configuration:

[[inputs.disk]]
  ## By default stats will be gathered for all mount points.
  ## Set mount_points will restrict the stats to only the specified mount points.
  # mount_points = ["/"]

  ## Ignore mount points by filesystem type.
  ignore_fs = ["tmpfs", "devtmpfs", "devfs", "overlay", "aufs", "squashfs"]

Docker container

To monitor the Docker engine host from within a container you will need to mount the host's filesystem into the container and set the HOST_PROC environment variable to the location of the /proc filesystem. If desired, you can also set the HOST_MOUNT_PREFIX environment variable to the prefix containing the /proc directory, when present this variable is stripped from the reported path tag.

docker run -v /:/hostfs:ro -e HOST_MOUNT_PREFIX=/hostfs -e HOST_PROC=/hostfs/proc telegraf

Metrics:

disk
- tags:
  - fstype (filesystem type)
  - device (device file)
  - path (mount point path)
  - mode (whether the mount is rw or ro)
- fields:
  - free (integer, bytes)
  - total (integer, bytes)
  - used (integer, bytes)
  - used_percent (float, percent)
  - inodes_free (integer, files)
  - inodes_total (integer, files)
  - inodes_used (integer, files)

Troubleshooting

On Linux, the list of disks is taken from the /proc/self/mounts file and a statfs call is made on the second column. If any expected filesystems are missing ensure that the telegraf user can read these files:

$ sudo -u telegraf cat /proc/self/mounts | grep sda2
/dev/sda2 /home ext4 rw,relatime,data=ordered 0 0
$ sudo -u telegraf stat /home

It may be desired to use POSIX ACLs to provide additional access:

sudo setfacl -R -m u:telegraf:X /var/lib/docker/volumes/

Example Output:

disk,fstype=hfs,mode=ro,path=/ free=398407520256i,inodes_free=97267461i,inodes_total=121847806i,inodes_used=24580345i,total=499088621568i,used=100418957312i,used_percent=20.131039916242397 1453832006274071563
disk,fstype=devfs,mode=rw,path=/dev free=0i,inodes_free=0i,inodes_total=628i,inodes_used=628i,total=185856i,used=185856i,used_percent=100 1453832006274137913
disk,fstype=autofs,mode=rw,path=/net free=0i,inodes_free=0i,inodes_total=0i,inodes_used=0i,total=0i,used=0i,used_percent=0 1453832006274157077
disk,fstype=autofs,mode=rw,path=/home free=0i,inodes_free=0i,inodes_total=0i,inodes_used=0i,total=0i,used=0i,used_percent=0 1453832006274169688

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