jfs_mkfs(8) create a JFS formatted partition


jfs_mkfs [options] device [ blocks ]


jfs_mkfs is used to create (format) a JFS partition. jfs_mkfs must be run as root.

device is the special file name corresponding to the actual device (e.g. /dev/hdb1) on which a JFS file system and/or JFS journal will be created. blocks is the number of blocks to be used for the file system. If omitted, jfs_mkfs automatically figures the file system size.

The default block size is 4096.


jfs_mkfs will destroy all data on the specified device!


Check the device for bad blocks before building the file system.

-j journal_device
Create the external JFS journal on journal_device , create the JFS file system on device , and attach the external journal to the file system.

-J journal-options
Create the JFS journal on its own device or attach an external JFS journal to the JFS file system using options specified on the command-line. The following journal options are supported:
Create an external JFS journal on the given device.
Attach an existing external JFS journal located on external-journal to the JFS file system that will be created on device. The external journal must already have been created using the command
jfs_mkfs -J journal_dev external-journal
Attach the external journal to the file system being created by using the command
jfs_mkfs -J device=external-journal device
Instead of specifying a device name directly, external-journal can also be specified by either LABEL=label or UUID=UUID to locate the external journal by either the volume label or UUID stored in the JFS external log superblock at the start of the journal. Use jfs_tune(8) to display a journal device's volume label and UUID. (See the -l, -L, and -U options of jfs_tune(8).)
Only one of the journal_dev or device= options can be given per jfs_mkfs issuance.

-L volume_label
Set the volume label for the newly formatted device.
If -L volume_label is used along with -J journal_device, the volume label of the specified external journal device will be set to volume_label. Otherwise, the volume label of the JFS file system will be set to volume_label.

Provide case-insensitive support for compatibility with OS/2.

Quiet execution - do not ask for confirmation before creating the file system.

-s log_size
Set the log size (in megabytes) of the inline log. If the -s option is not used, the default log size is 0.4% of the aggregate size.

Print version information and exit (regardless of any other chosen options).


Format 3rd partition on 2nd hard disk with the volume label "JFS_hdb3":

jfs_mkfs -L JFS_hdb3 /dev/hdb3

Format 5th partition on 1st hard disk, verifying each block created:

jfs_mkfs -c /dev/hda5

Format 3rd partition on 2nd hard disk as external journal, format 4th partition on 1st hard disk as JFS file system, and attach the external journal to the file system:

jfs_mkfs -j /dev/hdb3 /dev/hda4


If you find a bug in JFS or jfs_mkfs, please report it via the bug tracking system ("Report Bugs" section) of the JFS project web site:


Please send as much pertinent information as possible including any error messages resulting from running jfs_mkfs.


Barry Arndt  ([email protected])
William Braswell, Jr.
jfs_mkfs is maintained by IBM.
See the JFS project web site for more details: