File System Manipulation

Monitor Disk Uasage

# du -h --max-depth=1

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