03-20-2008
cat /dev/null
Hi,
Excuse my ignorance here - I'm a networks man and my knowledge of all things unix is somewhat limited.
We have a very large file (/var/tmp/mond.log) that we need to zero - does the "cat /dev/null > /var/tmp/mond.log" command achieve this?
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LEARN ABOUT CENTOS
xfs_estimate
xfs_estimate(8) System Manager's Manual xfs_estimate(8)
NAME
xfs_estimate - estimate the space that an XFS filesystem will take
SYNOPSIS
xfs_estimate [ -h ] [ -b blocksize ] [ -i logsize ]
[ -e logsize ] [ -v ] directory ...
xfs_estimate -V
DESCRIPTION
For each directory argument, xfs_estimate estimates the space that directory would take if it were copied to an XFS filesystem. xfs_esti-
mate does not cross mount points. The following definitions are used:
KB = *1024
MB = *1024*1024
GB = *1024*1024*1024
The xfs_estimate options are:
-b blocksize
Use blocksize instead of the default blocksize of 4096 bytes. The modifier k can be used after the number to indicate multiplica-
tion by 1024. For example,
xfs_estimate -b 64k /
requests an estimate of the space required by the directory / on an XFS filesystem using a blocksize of 64K (65536) bytes.
-v Display more information, formatted.
-h Display usage message.
-i, -e logsize
Use logsize instead of the default log size of 1000 blocks. -i refers to an internal log, while -e refers to an external log. The
modifiers k or m can be used after the number to indicate multiplication by 1024 or 1048576, respectively.
For example,
xfs_estimate -i 1m /
requests an estimate of the space required by the directory / on an XFS filesystem using an internal log of 1 megabyte.
-V Print the version number and exits.
EXAMPLES
% xfs_estimate -e 10m /var/tmp
/var/tmp will take about 4.2 megabytes
with the external log using 2560 blocks or about 10.0 megabytes
% xfs_estimate -v -e 10m /var/tmp
directory bsize blocks megabytes logsize
/var/tmp 4096 792 4.0MB 10485760
% xfs_estimate -v /var/tmp
directory bsize blocks megabytes logsize
/var/tmp 4096 3352 14.0MB 10485760
% xfs_estimate /var/tmp
/var/tmp will take about 14.0 megabytes
xfs_estimate(8)