Bash monitor disk usage - linux

Question

I bought a NAS box which has a cut down version of debian on it.
It ran out of space the other day and I did not realise. I am basically wanting to write a bash script that will alert me whenever the disk gets over 90% full.
Is anyone aware of a script that will do this or give me some advice on writing one?

Answer 1

#!/bin/bash
source /etc/profile
# Device to check
devname="/dev/sdb1"
let p=`df -k $devname | grep -v ^File | awk '{printf ("%i",$3*100 / $2); }'`
if [ $p -ge 90 ]
then
df -h $devname | mail -s "Low on space" my#email.com
fi
Crontab this to run however often you want an alert
EDIT: For multiple disks
#!/bin/bash
source /etc/profile
# Devices to check
devnames="/dev/sdb1 /dev/sda1"
for devname in $devnames
do
let p=`df -k $devname | grep -v ^File | awk '{printf ("%i",$3*100 / $2); }'`
if [ $p -ge 90 ]
then
df -h $devname | mail -s "$devname is low on space" my#email.com
fi
done

Answer 2

I tried to use Erik's answer but had issues with devices having long names which wraps the numbers and causes script to fail, also the math looked wrong to me and didn't match the percentages reported by df itself.
Here's an update to his script:
#!/bin/bash
source /etc/profile
# Devices to check
devnames="/dev/sda1 /dev/md1 /dev/mapper/vg1-mysqldisk1 /dev/mapper/vg4-ctsshare1 /dev/mapper/vg2-jbossdisk1 /dev/mapper/vg5-ctsarchive1 /dev/mapper/vg3-muledisk1"
for devname in $devnames
do
let p=`df -Pk $devname | grep -v ^File | awk '{printf ("%i", $5) }'`
if [ $p -ge 70 ]
then
df -h $devname | mail -s "$devname is low on space" my#email.com
fi
done
Key changes are changed df -k to df -Pk to avoid line wrapping and simplified the awk to use pre-calc'd percent instead of recalcing.

Answer 3

You could also use Monit for this kind of job. It's a "free open source utility for managing and monitoring, processes, programs, files, directories and filesystems on a UNIX system".

Answer 4

Based on #Erik answer, here is my version with variables :
#!/bin/bash
DEVNAMES="/ /home"
THRESHOLD=80
EMAIL=you#email.com
host=$(hostname)
for devname in $DEVNAMES
do
current=$(df $devname | grep / | awk '{ print $5}' | sed 's/%//g')
if [ "$current" -gt "$THRESHOLD" ] ; then
mail -s "Disk space alert on $host" "$EMAIL" << EOF
WARNING: partition $devname on $host is $current% !!
To list big files (>100Mo) :
find $devname -xdev -type f -size +100M
EOF
fi
done
And if you do not have the mail command on your server, you can send email via SMPT with swaks :
swaks --from "$EMAIL" --to "$EMAIL" --server "TheServer" --auth LOGIN --auth-user "TheUser" --auth-password "ThePasswrd" --h-Subject "Disk space alert on $host" --body - << EOF

Answer 5

#!/bin/bash
DEVNAMES=$(df --output=source | grep ^/dev)
THRESHOLD=90
EMAIL=your#email
HOST=$(hostname)
for devname in $DEVNAMES
do
current=$(df $devname | awk 'NR>1 {printf "%i",$5}')
[ "$current" -gt "$THRESHOLD" ] && warn="WARNING: partition $devname on $HOST is $current% !! \n$warn"
done
[ "$warn" ] && echo -e "$warn" | mail -s "Disk space alert on $HOST" $EMAIL
Based on previous answers, here's my version with following changes:
Automatically checks all mounted devices
Sends only one mail per check, regardless of how many devices are over the threshold
Code generally tidied up