=====File System Manipulation=====

===Monitor Disk Uasage===

<code># du -h --max-depth=1 </code>


===Create an F/S in RAM===

Makes a partition in ram which is useful if you need a temporary working space, as read/write RAM access is fast.

  # mount -t tmpfs tmpfs /mnt -o size=1024m



===Harddisk Backup/Restore===

Backup an entire harddisk

  # dd if=/dev/sda of=/media/disk/backup/sda.backup

Restore an entire harddisk

  # dd if=/media/disk/backup/sda.backup of=/dev/sda



If you zero out the blank space first, you get great space savings

  # dd if=/dev/zero of=/tmp/delete.me bs=8M; rm delete.me

  # dd if=/dev/hda conv=sync,noerror bs=64K | gzip -c > /mnt/sda1/hda.img.gz



===Setting reserved blocks percentage to 1%===

before:

  [root@metstore ~]# df -hT /store*

  Filesystem                Type    Size  Used Avail Use% Mounted on

  /dev/mapper/vg1-LogVol01  ext3    388G   84G  284G  23% /store1

  /dev/mapper/vg2-LogVol00  ext3    395G  498M  374G   1% /store2



  [root@metstore ~]# tune2fs -m 1 /dev/mapper/vg1-LogVol01 ; tune2fs -m 1 /dev/mapper/vg2-LogVol00

  Setting reserved blocks percentage to 1% (1049640 blocks)



after:

  [root@metstore ~]# df -hT /store*

  Filesystem                Type    Size  Used Avail Use% Mounted on

  /dev/mapper/vg1-LogVol01  ext3    388G   84G  300G  22% /store1

  /dev/mapper/vg2-LogVol00  ext3    395G  498M  390G   1% /store2



===Testing hard disk writing speed===

  # time dd if=/dev/zero of=TEST bs=4k count=512000

or

  # time dd if=/dev/zero of=blah.out oflag=direct bs=256M count=1