Discrepancy in free space reported by df and du

Description

Error Message

Resolution

It is common for applications to acquire an exclusive use lock on a temporary file by opening it and deleting it immediately The file will still be opened by the process, but no other process can get hold of it because it no longer exists in the directory structure. For example,

# cd /voltmp

# mkfile 2000m tmpfile

# sleep 999999 < tmpfile&

[5] 28882

# rm tmpfile

# df -k /voltmp

Filesystem kbytes used avail capacity Mounted on

/dev/vx/dsk/datadg/voltmp

6291456 5132210 1086799 83% /voltmp

# du -sk /voltmp

3066193 /voltmp

There is a discrepancy of 2GB in the free space reported by df and du.

pfiles shows that the file is still opened by process 28882, but there is no trace of it in the directory structure.

jacaranda# pfiles 28882

28882: sleep 999998888

Current rlimit: 256 file descriptors

0: S_IFREG mode:0600 dev:223,55022 ino:8 uid:0 gid:1size:2097152000 <<<< This inode is stillopened.

O_RDONLY|O_LARGEFILE

1: S_IFCHR mode:0620 dev:223,0 ino:77990 uid:0 gid:7rdev:24,5

O_RDWR

2: S_IFCHR mode:0620 dev:223,0 ino:77990 uid:0 gid:7rdev:24,5

O_RDWR

5: S_IFCHR mode:0620 dev:223,0 ino:77990 uid:0 gid:7rdev:24,5

O_RDWR

8: S_IFREG mode:0644 dev:223,0 ino:231957 uid:0 gid:0size:4464

O_RDWR

9: S_IFREG mode:0644 dev:223,0 ino:231957 uid:0 gid:0size:4464

O_RDWR

The following script can be used to search all processes for the missing files. The script is named as "missing inodes".

---------- Begin script missinginodes--------------

#!/bin/ksh

# This script will search deleted files that is stillopened by processes

# in the specified mounted file system. Thosedeleted but still kept open

# files will cause a discrepancy in the free space asreported by df and du.

# This script will create a temp files in /tmp withname started

# with missinginodes to store the inode list. Ifthere is already

# an ilist file (e.g. /tmp/missinginodes.1232), youcan reuse the

# file with the -i option.

PATH=/usr/bin; export PATH

CMDNAME=´basename $0´

USAGE="Usage: $CMDNAME [-i ]"

ILISTFILE=

while getopts i: option

do

case $option in

i) ILISTFILE=$OPTARG

;;

?) echo $USAGE

exit 1;;

esac

done

shift $(($OPTIND -1))

if [ $# -lt 1 ]

then

echo "$USAGE"

exit 1

fi

MNTPOINT=$1

if ! cat /etc/mnttab | awk '{print $2}' | grep$MNTPOINT > /dev/null

then

echo "$MNTPOINT is not a mountpoint"

exit 1

fi

DEVICE=´df -k $MNTPOINT | tail +2 | head -1 |awk '{print $1}'´

DEVINODE=´ls -lL $DEVICE | awk '{print $5, $6}'| sed 's/, */,/

s/ [^ ]*$//

s/ //g' ´

if [ -z "$ILISTFILE" ]

then

ILISTFILE=/tmp/$CMDNAME.$$

echo "Generating inodelist...."

find $MNTPOINT -mount -ls >$ILISTFILE

fi

echo "Searching processes with deletedfiles..."

(cd /proc; ls ) | while read p

do

MESG=´pfiles $p | grep"S_IFREG.*dev:$DEVINODE"´

if [ $? -eq 0 ]

then

echo "$MESG" | while read m

do

ino=´echo "$m" | sed's/.*ino:$[0-9]*$.*/\1/'´

if ! grep -l "^ *$ino " $ILISTFILE >/dev/null

then

echo Process $p holds missing inode$ino

echo " $m"

fi

done

fi

done

----------- End script missinginodes-------------

Run this script against the file system mountpoint.

jacaranda# missinginodes /voltmp

Generating inode list....

Searching processes with deletedfiles...

Process 28882 holds missing inode 8

0: S_IFREG mode:0600 dev:223,55022 ino:8 uid:0 gid:1size:2097152000

It shows that process 28882 is holding the missing inode8 which has a size of 2GB.

Issue/Introduction

Discrepancy in free space reported by df and du

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