how i know How Much Disk Space Left On Hard Drive

You need to use the df command. It shows the amount of disk space available on the currently mounted file system. df is used to show or find out following information:

1. Used and available space.


2. File system mount points.


3. File system capacity.


4. The number of inodes available.


5. Find of whether there is sufficient space to upgrade or install new apps.

Syntax

The basic syntax is as follows:

df

df /path/to/dev

df [options]

df [options] /path/to/dev

Examples

Type the following command:
# df

# df -H

Sample outputs:

 

The following example will provide information only for the partition/device that contains the /home directory:
# df /home

# df -h /home

To see inode usage instead of block usage, type:
# df -i

# df -i /

# df -ih /

# df -i /dev/md0

Sample outputs:

Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/md0 7872512 35813 7836699 1% /

Pass the -T to find out file system type:
# df -T -h

Sample outputs:

Filesystem Type Size Used Avail Use% Mounted on
/dev/md0 ext4 119G 1.8G 111G 2% /
tmpfs tmpfs 1002M 0 1002M 0% /lib/init/rw
udev tmpfs 1000M 260K 1000M 1% /dev
tmpfs tmpfs 1002M 0 1002M 0% /dev/shm
/dev/md2 ext4 1.5T 658G 745G 47% /data
/dev/mapper/cryptvg-mybackup
 ext3 591G 78G 484G 14% /securebackup

df command options

From the df command man page:

 -a, --all include dummy file systems
 -B, --block-size=SIZE use SIZE-byte blocks
 --total produce a grand total
 -h, --human-readable print sizes in human readable format (e.g., 1K 234M 2G)
 -H, --si likewise, but use powers of 1000 not 1024
 -i, --inodes list inode information instead of block usage
 -k like --block-size=1K
 -l, --local limit listing to local file systems
 --no-sync do not invoke sync before getting usage info (default)
 -P, --portability use the POSIX output format
 --sync invoke sync before getting usage info
 -t, --type=TYPE limit listing to file systems of type TYPE
 -T, --print-type print file system type
 -x, --exclude-type=TYPE limit listing to file systems not of type TYPE

how i know How Much Disk Space Left On Hard Drive