title: Increasing the size of a filesystem in AIX - chfs and df commands
body: <p>the command <code>df /</code> displays the following output on my host. </p>
  
  <p><code>Filesystem    512-blocks      Free %Used    Iused %Iused Mounted on
  /dev/hd4         5177344   1065096   80%    13676     9% /</code></p>
  
  <p>according to the manpage of df, by default all sizes are displayed in number of 512 blocks. Therefore, my / filesystem has 1065096 512-blocks empty. Now say I want to add one more block of 512 bytes to the filesystem, I will use the chfs command to increase the size of the filesystem. Below:</p>
  
  <p><code>chfs -a size=+1 /</code></p>
  
  <p>the man page of chfs says that sizes can be increased in number of 512 byte blocks if the number is not followed by M or G. Here is what happened when I ran the above mentioned command. </p>
  
  <p><code>$ df /</code></p>
  
  <p><code>Filesystem    512-blocks      Free %Used    Iused %Iused Mounted on
  /dev/hd4         5177344   1065096   80%    13676     9% /</code></p>
  
  <p><code>$ chfs -a size=+1 /
  Filesystem size changed to 5177344</code></p>
  
  <p><code>$ df /</code></p>
  
  <p><code>Filesystem    512-blocks      Free %Used    Iused %Iused Mounted on
  /dev/hd4         5177344   1065096   80%    13676     9% /</code></p>
  
  <p><code>$ expr 1065096 \- 999568
  65528</code></p>
  
  <p>Can someone explain how instead of increasing by one 512 block, the size increased by 127 512 blocks?</p>