.TH mmchfs 12/01/06
mmchfs Command
.SH "Name"
.PP
\fBmmchfs\fR - Changes the attributes of a GPFS file system.
.SH "Synopsis"
.PP
\fBmmchfs\fR \fIDevice\fR [\fB-A {\fR\fByes\fR | \fBno |
automount}\fR] [\fB-E {\fR\fByes |
\fR\fBno\fR\fB}\fR] [\fB-D {\fR\fBnfs4\fR |
\fBposix\fR\fB}\fR] [\fB-F\fR
\fIMaxNumInodes\fR[:\fINumInodesToPreallocate\fR]]
[\fB-k {\fR\fBposix\fR\fB | nfs4 | all}\fR] [\fB-K
{no | \fR\fBwhenpossible\fR\fB | always}\fR] [\fB-m\fR
\fIDefaultMetadataReplicas\fR] [\fB-o\fR
\fIMountOptions\fR] [\fB-Q {yes | \fR\fBno}\fR]
[\fB-r\fR \fIDefaultDataReplicas\fR] [\fB-S\fR
\fB{yes\fR\fB | no} ]\fR [\fB-T\fR
\fIMountpoint\fR] [\fB-V\fR] [\fB-z
{\fR\fByes\fR \fB| no}\fR]
.PP
Or,
.PP
\fBmmchfs\fR \fIDevice\fR [\fB-W \fR
\fINewDeviceName\fR]
.SH "Description"
.PP
Use the \fBmmchfs\fR command to change the attributes of a GPFS file
system.
.PP
All files created after issuing the \fBmmchfs\fR command take on the new
attributes. Existing files are not affected. Use the
\fBmmchattr\fR command to change the replication factor of existing
files.
.SH "Parameters"
.PP
.RS +3
\fB\fIDevice\fR
\fR
.RE
.RS +9
The device name of the file system to be changed. 
.PP
File system names need not be fully-qualified. \fBfs0\fR is as
acceptable as \fB/dev/fs0\fR. However, file system names must be
unique across GPFS clusters.
.PP
This must be the first parameter.
.RE
.SH "Options"
.PP
.RS +3
\fB-A {yes | \fBno\fR | automount}
\fR
.RE
.RS +9
Indicates when the file system is to be mounted:
.PP
.RS +3
\fByes
\fR
.RE
.RS +9
When the GPFS daemon starts.
.RE
.PP
.RS +3
\fBno
\fR
.RE
.RS +9
Manual mount.
.RE
.PP
.RS +3
\fBautomount
\fR
.RE
.RS +9
When the file system is first accessed.
.RE
.RE
.PP
.RS +3
\fB-D {nfs4 | \fBposix\fR}
\fR
.RE
.RS +9
Specifies whether a 'deny-write open lock' will block writes,
which is expected and required by NFS V4. File systems supporting NFS
V4 must have \fB-D nfs4\fR set. The option \fB-D posix\fR allows
NFS writes even in the presence of a deny-write open lock. If you
intend to export the file system using NFS V4 or Samba, you must use \fB-D
nfs4\fR. For NFS V3 (or if the file system is not NFS exported at
all) use \fB-D posix\fR.
.RE
.PP
.RS +3
\fB-E {yes | \fBno\fR}
\fR
.RE
.RS +9
Specifies whether to report exact \fBmtime\fR values. If \fB-E
no\fR is specified, the \fBmtime\fR value is periodically updated.
If you desire to always display exact modification times, specify the \fB-E
yes\fR option.
.RE
.PP
.RS +3
\fB-F \fIMaxNumInodes\fR[:\fINumInodesToPreallocate\fR]
\fR
.RE
.RS +9
\fIMaxNumInodes\fR specifies the maximum number of files that can be
created. Allowable values range from the current number of created
inodes (determined by issuing the \fBmmdf\fR command with the \fB-F\fR
option), through the maximum number of files possibly supported as constrained
by the formula:
.PP
\fBmaximum number of files = (total file system space/2) / (inode size +
subblock size)\fR
.PP
If your file system has additional disks added or the number of inodes was
insufficiently sized at file system creation, you may change the number of
inodes and hence the maximum number of files that can be created.
.PP
For file systems that will be doing parallel file creates, if the total
number of free inodes is not greater than 5% of the total number of inodes,
there is the potential for slowdown in file system access. Take this
into consideration when changing your file system.
.PP
\fINumInodesToPreallocate\fR specifies the number of inodes that will be
preallocated by the system right away. If this number is not specified,
GPFS allocates inodes dynamically as needed.
.PP
The \fIMaxNumInodes\fR and \fINumInodesToPreallocate\fR values can be
specified with a suffix, for example 100K or 2M.
.RE
.PP
.RS +3
\fB\fB-k {\fR\fBposix\fR\fB | nfs4 | all}\fR
\fR
.RE
.RS +9
Specifies the type of authorization supported by the file system:
.PP
.RS +3
\fBposix
\fR
.RE
.RS +9
Traditional GPFS ACLs only (NFS V4 ACLs are not allowed).
Authorization controls are unchanged from earlier releases.
.RE
.PP
.RS +3
\fBnfs4
\fR
.RE
.RS +9
Support for NFS V4 ACLs only. Users are not allowed to assign
traditional GPFS ACLs to any file system objects (directories and individual
files).
.RE
.PP
.RS +3
\fBall
\fR
.RE
.RS +9
Any supported ACL type is permitted. This includes traditional GPFS
(\fBposix\fR) and NFS V4 ACLs (\fBnfs4\fR).
.PP
The administrator is allowing a mixture of ACL types. For example,
\fBfileA\fR may have a \fBposix\fR ACL, while \fBfileB\fR in the same
file system may have an NFS V4 ACL, implying different access characteristics
for each file depending on the ACL type that is currently assigned.
.RE
.PP
Neither \fBnfs4\fR nor \fBall\fR should be specified here unless the
file system is going to be exported to NFS V4 clients. NFS V4 ACLs
affect file attributes (mode) and have access and authorization
characteristics that are different from traditional GPFS ACLs.
.RE
.PP
.RS +3
\fB\fB-K {no | \fR\fBwhenpossible\fR\fB | always}\fR
\fR
.RE
.RS +9
Specifies whether strict replication is to be enforced:
.PP
.RS +3
\fBno
\fR
.RE
.RS +9
Strict replication is not enforced. GPFS will try to create the
needed number of replicas, but will still return EOK as long as it can
allocate at least one replica.
.RE
.PP
.RS +3
\fBwhenpossible
\fR
.RE
.RS +9
Strict replication is enforced provided the disk configuration allows
it. If there is only one failure group, strict replication will not be
enforced.
.RE
.PP
.RS +3
\fBalways
\fR
.RE
.RS +9
Strict replication is enforced.
.RE
.RE
.PP
.RS +3
\fB-m \fIDefaultMetaDataReplicas\fR
\fR
.RE
.RS +9
Changes the default number of metadata replicas. Valid values are 1
and 2 but cannot exceed the values of \fIMaxMetaDataReplicas\fR set when
the file system was created.
.RE
.PP
.RS +3
\fB-o \fIMountOptions\fR
\fR
.RE
.RS +9
Specifies the mount options to pass to the mount command when mounting the
file system. For a detailed description of the available mount options,
see GPFS-specific mount options.
.RE
.PP
.RS +3
\fB-Q {yes | no}
\fR
.RE
.RS +9
If \fByes\fR is specified, quotas are activated automatically when the
file system is mounted. If \fBno\fR is specified, the quota files
remain in the file system, but are not used.
.PP
To activate quota management:
.RS +3
.HP 3
1. Unmount the file system everywhere
.HP 3
2. Run the command \fBmmchfs -Q yes\fR
.HP 3
3. Remount the file system, activating the new quota files
.HP 3
4. Compile inode and disk block statistics using the \fBmmcheckquota\fR
command. Use these values as a reference to establish realistic quota
values when issuing the \fBmmedquota\fR and \fBmmdefedquota\fR
commands.
.HP 3
5. For default quotas:
.RS +3
.HP 3
a. Issue the \fBmmdefedquota\fR command to establish default quota values
.HP 3
b. Issue the \fBmmdefquotaon -d\fR command to activate default quotas
.RE
.HP 3
6. For explicit quotas:
.RS +3
.HP 3
a. Issue the \fBmmedquota\fR command to establish quota values
.RE
.RE
.PP
To deactivate quota management:
.RS +3
.HP 3
1. Unmount the file system everywhere
.HP 3
2. Run the command \fBmmchfs -Q no\fR
.HP 3
3. Remount the file system, deactivating the quota files
.RE
.RE
.PP
.RS +3
\fB-r \fIDefaultDataReplicas\fR
\fR
.RE
.RS +9
Changes the default number of data replicas. Valid values are 1 and
2 but cannot exceed the values of \fIMaxDataReplicas\fR set when the file
system was created.
.RE
.PP
.RS +3
\fB-S {yes | no}
\fR
.RE
.RS +9
Suppress the periodic updating of the value of \fBatime\fR as reported
by the \fBgpfs_stat()\fR, \fBgpfs_fstat()\fR, \fBstat()\fR, and
\fBfstat()\fR calls. If \fByes\fR is specified these calls report
the last time the file was accessed when the file system was mounted with the
\fB-S no\fR option.
.RE
.PP
.RS +3
\fB-T \fIMountpoint\fR
\fR
.RE
.RS +9
Change the mount point of the file system starting at the next mount of
the file system.
.PP
The file system must be unmounted on all nodes prior to issuing the
command.
.RE
.PP
.RS +3
\fB-V
\fR
.RE
.RS +9
After migration, change the file system format to the latest format
supported by the currently installed level of GPFS. This causes the
file system to become permanently incompatible with earlier releases of
GPFS.
.PP
Before issuing the \fB-V\fR option, see the \fIGeneral Parallel File
System: Concepts, Planning, and Installation Guide\fR and search for
\fIMigration, coexistence and compatibility\fR.
.RE
.PP
.RS +3
\fB-W \fINewDeviceName\fR
\fR
.RE
.RS +9
Assign \fINewDeviceName\fR to be the device name for the file
system.
.RE
.PP
.RS +3
\fB-z {yes | no}
\fR
.RE
.RS +9
Enable or disable DMAPI on the file system. For further information
on DMAPI for GPFS, see the \fIGeneral Parallel File System: Data
Management API Guide\fR.
.RE
.SH "Exit status"
.PP
.PP
.RS +3
\fB0
\fR
.RE
.RS +9
Successful completion.
.RE
.PP
.RS +3
\fBnonzero
\fR
.RE
.RS +9
A failure has occurred.
.RE
.SH "Security"
.PP
You must have root authority to run the \fBmmchfs\fR command.
.PP
You may issue the \fBmmchfs\fR command from any node in the GPFS
cluster.
.PP
When using the \fBrcp\fR and \fBrsh\fR commands for remote
communication, a properly configured \fB.rhosts\fR file must exist
in the root user's home directory on each node in the GPFS
cluster. If you have designated the use of a different remote
communication program on either the \fBmmcrcluster\fR or the
\fBmmchcluster\fR command, you must ensure:
.RS +3
.HP 3
1. Proper authorization is granted to all nodes in the GPFS cluster.
.HP 3
2. The nodes in the GPFS cluster can communicate without the use of a
password, and without any extraneous messages.
.RE
.PP
When considering data replication for files accessible to SANergy, see
\fISANergy export considerations\fR in \fIGeneral Parallel File
System: Advanced Administration Guide\fR.
.SH "Examples"
.PP
To change the default replicas for metadata to 2 and the default replicas
for data to 2 for new files created in the \fBfs0\fR file system, issue
this command:
.sp
.nf
mmchfs fs0 -m 2 -r 2
.fi
.sp
.PP
To confirm the change, issue this command:
.sp
.nf
mmlsfs fs0 -m -r
.fi
.sp
.PP
The system displays information similar to:
.sp
.nf
flag value          description
---- -------------- -----------------------------------
 -m  2              Default number of metadata replicas
 -r  2              Default number of data replicas
.fi
.sp
.SH "See also"
.PP
mmcrfs Command
.PP
mmdelfs Command
.PP
mmdf Command
.PP
mmfsck Command
.PP
mmlsfs Command
.SH "Location"
.PP
\fB/usr/lpp/mmfs/bin\fR