chfs Command

Purpose

Changes attributes of a file system.

Syntax

chfs [ -n NodeName ] [ -m NewMountPoint ] [ -u MountGroup ] [ -A { yes | no } ] [ -p { ro | rw } ] [ -t { yes | no } ] [ -a Attribute=Value ] [ -d Attribute ] FileSystem

Description

The chfs command changes the attributes of a file system. The new mount point, automatic mounts, permissions, and file system size can be set or changed. The FileSystem parameter specifies the name of the file system, expressed as a mount point.

Some file system attributes are set at the time the file system is created and cannot be changed. For the Journaled File System (JFS), such attributes include the fragment size, block size, number of bytes per i-node, compression, and the minimum file system size.

You can use the Web-based System Manager File Systems application (wsm fs fast path) to run this command. You could also use the System Management Interface Tool (SMIT) smit chhfs fast path to run this command.

Flags

-a Attribute=Value

Specifies the Attribute=Value pairs; dependent on virtual file system type. To specify more than one Attribute=Value pair, provide multiple -a Attribute=Value parameters.

The following attribute/value pairs are specific to the Journaled File System (JFS):

-a Size=NewSize

Specifies the size of the Journaled File System in 512-byte blocks. If Value begins with a + it is interpreted as a rquest to increase the file system size by the specified amount. If the specified size is not evenly divisible by the physical partition size, it is rounded up to the closest number that is evenly divisible.

The maximum size of a JFS file system is a function of its fragment size and the nbpi value. These values yield the following size restrictions:

nbpi	Fragment size in bytes	Maximum size in 512-byte blocks
512	512, 1024, 2048, 4096	16777216
1024	512, 1024, 2048, 4096	33554432
2048	512, 1024, 2048, 4096	67108864
4096	512, 1024, 2048, 4096	134217728
8192	512, 1024, 2048, 4096	268435456
16384	512	268435456
16384	1024, 2048, 4096	536870912
32768	512	268435456
32768	1024	536870912
32768	2048, 4096	1073741824
65536, 131072	512	268435456
65536, 131072	1024	536870912
65536, 131072	2048	1073741824
65536, 131072	4096	2147483648
AIX 4.1 is limited to NBPI values from 512 to 16384. In AIX4.3, you can have NBPI values from 512 to 128K, with corresponding maximum file system sizes.

The volume group in which the file system resides defines a maximum logical volume size and also limits the file system size.

-a log=LVName

Specifies the full path name of the filesystem logging logical volume name of the existing log to be used. The log device for this filesystem must reside on the same volume group as the filesystem

-A

Specifies the attributes for auto-mount.

yes

File system is automatically mounted at system restart.

no

File system is not mounted at system restart.

-d Attribute

Deletes the specified attribute from the /etc/filesystems file for the specified file system.

-m NewMountPoint

Specifies the new mount point.

-n NodeName

Specifies a node name for the specified file system. The node name attribute in the /etc/filesystems file is updated with the new name. The node name attribute is specific to certain remote virtual file system types, such as the NFS (Network File System) virtual file system type.

-p

Sets the permissions for the file system.

ro

Specifies read-only permissions.

rw

Specifies read-write permissions.

-t

Sets the accounting attribute for the specified file system:

yes

File system accounting is to be processed by the accounting subsystem.

no

File system accounting is not to be processed by the accounting subsystem; this is the default.

-u MountGroup

Specifies the mount group. Mount groups are used to group related mounts, so that they can be mounted as one instead of mounting each individually. For example, if several scratch file systems always need to be mounted together when performing certain tests, they can each be placed in the test mount group. They can then all be mounted with a single command, such as the mount -t test command.

Examples

1. To change the file system size of the /test Journaled File System, enter:

   chfs -a size=24576 /test

   This command changes the size of the /test Journaled File System to 24576 512-byte blocks, or 12MB (provided it was previously no larger than this).
2. To increase the size of the /test Journaled File System, enter:

   chfs -a size=+8192 /test

   This command increases the size of the /test Journaled File System by 8192 512-byte blocks, or 4MB.
3. To change the mount point of a file system, enter:

   chfs -m /test2 /test

   This command changes the mount point of a file system from /test to /test2.
4. To delete the accounting attribute from a file system, enter:

   chfs -d account /home

   This command removes the accounting attribute from the /home file system. The accounting attribute is deleted from the /home: stanza of the /etc/filesystems file.

File

Related Information

The crfs command, mkfs command, mklv command.

The Accounting Overview in AIX Version 4.3 System Management Guide: Operating System and Devices explains the file system accounting subsystem.

The File Systems Overview for System Management in AIX Version 4.3 System Management Guide: Operating System and Devices explains file system types, management, structure, and maintenance.

Setting up and running Web-based System Management in AIX Version 4.3 System Management Guide: Operating System and Devices.

The System Management Interface Tool (SMIT): Overview in AIX Version 4.3 System Management Guide: Operating System and Devices explains SMIT structure, main menus, and tasks.