zdsfs - Mount a z/OS DASD

LPAR mode z/VM guest KVM guest

Use the zdsfs command to mount z/OS DASDs as a Linux® file system.

The zdsfs file system translates the z/OS data sets, which are stored on the DASDs in records of arbitrary or even variable size, into Linux semantics.

Through the zdsfs file system, applications on Linux can read z/OS physical sequential data sets (PS) and partitioned data sets (PDS) on the DASD. In the Linux file system, physical sequential data sets are represented as files. Partitioned data sets are represented as directories that contain the PDS members as files. Other z/OS data set formats, such as extended format data sets or VSAM data sets, are not supported. zdsfs is optimized for sequential read access.

Attention:

To avoid data inconsistencies, set the DASDs offline in z/OS before you mount them in Linux.
Through the zdsfs file system, the whole DASDs are accessible to Linux, but the access is not controlled by z/OS auditing mechanisms.
To avoid security problems, you might want to dedicate the z/OS DASDs only for providing data for Linux.

Per default, only the Linux user who mounts the zdsfs file system has access to it.

Tip: If you want to grant a user group access to the zdsfs file system, mount it with the fuse options default_permissions, allow_other, and gid.

To unmount file systems that you mounted with zdsfs, you can use umount.

See z/OS DFSMS Using Data Sets, SC26-7410 for more information about z/OS data sets.

Before you begin:

The FUSE library must be installed on your system. Ubuntu Server installs this library for you by default. You can also obtain it from sourceforge at sourceforge.net/projects/fuse.
To access full ECKD tracks, the raw-track access mode of the DASD must be enabled.
Make sure that the DASD is set offline when you enable the raw-track access mode.
The DASD must be online.
Tip: You can use the chccwdev command to enable the raw-track access mode and set the device online afterward in one step.

Set the DASD offline in z/OS before you set it online in Linux.
You must have the appropriate read permissions for the device node.

zdsfs syntax

where:

<zdsfs-options>

zdsfs-specific options.

-o ignore_incomplete: represents all complete data sets in the file system, even if there are incomplete data sets. Incomplete data sets are not represented.
In z/OS, data sets might be distributed over different DASDs. For each incomplete data set, a warning message is issued to the standard error stream. If there are incomplete data sets and this option is not specified, the zdsfs command returns with an error.
-o rdw: keeps record descriptor words (RDWs) of data sets that are stored by using the z/OS concept of variable record lengths.
-o tracks=<n>: specifies the track buffer size in tracks. The default is 128 tracks.
zdsfs allocates a track buffer of <n>*120 KB for each open file to store and extract the user data. Increasing the track buffer size might improve your system performance.
-o seekbuffer=<s>: sets the maximum seek history buffer size in bytes. The default is 1,048,576 B.
zdsfs saves offset information about a data set in the seek history buffer to speed up the performance of a seek operation.
-o check_host_count: checks the host-access open count to ensure that the device is not online to another operating system instance. The operation is canceled if another operating system instance is accessing the volume.

<fuse-options>

options for FUSE. The following options are supported by the zdsfs command. To use an option, it must also be supported by the version of FUSE that is installed.

-d or -o debug: enables debug output (implies -f).
-f: runs the command as a foreground operation.
-o allow_other: allows access to other users.
-o allow_root: allows access to root.
-o nonempty: allows mounts over files and non-empty directories.
-o default_permissions: enables permission checking by the kernel.
-o max_read=<n>: sets maximum size of read requests.
-o kernel_cache: caches files in the kernel.
-o [no]auto_cache: enables or disables caching based on modification times.
-o umask=<mask>: sets file permissions (octal).
-o uid=<n>: sets the file owner.
-o gid=<n>: sets the file group.
-o max_write=<n>: sets the maximum size of write requests.
-o max_readahead=<n>: sets the maximum readahead value.
-o async_read: performs reads asynchronously (default).
-o sync_read: performs reads synchronously.

<node-list>

one or more device nodes for the DASDs, separated by blanks.

<file-name>

a file that contains a node list.

<mount-point>

the mount point in the Linux file system where you want to mount the z/OS data sets.

-h or --help

displays help information for the command. To view the man page, enter man zdsfs.

-v or --version

displays version information for the command.

File characteristics

There are two ways to handle the z/OS characteristics of a file:

The file metadata.txt:
The metadata.txt file is in the root directory of the mount point. It contains one row for each file or directory, where:
dsn
specifies
- the name of the file in the form <file-name> for z/OS physical sequential data sets.
- the name of the directory in the form <directory-name>, and the name of a file in that directory in the form <directory-name>(<file-name>) for z/OS partitioned data sets.
dsorg

specifies the organization of the file. The organization is PO for a directory, and PS for a file.

lrecl

specifies the record length of the file.

recfm

specifies the z/OS record format of the file. Supported record formats are: V, F, U, B, S, A, and M.
Example:
```
dsn=FOOBAR.TESTF.TXT,recfm=FB,lrecl=80,dsorg=PS
dsn=FOOBAR.TESTVB.TXT,recfm=VB,lrecl=100,dsorg=PS
dsn=FOOBAR.PDSF.DAT,recfm=F,lrecl=80,dsorg=PO
dsn=FOOBAR.PDSF.DAT(TEST1),recfm=F,lrecl=80,dsorg=PS
dsn=FOOBAR.PDSF.DAT(TEST2),recfm=F,lrecl=80,dsorg=PS
dsn=FOOBAR.PDSF.DAT(TEXT3),recfm=F,lrecl=80,dsorg=PS
```
Extended attributes:

user.dsorg

specifies the organization of the file.

user.lrecl

specifies the record length of the file.

user.recfm

specifies the z/OS record format of the file.

You can use the following system calls to work with extended attributes:

listxattr

to list the current values of all extended attributes.

getxattr

to read the current value of a particular extended attribute.

You can use these system calls through the getfattr command. For more information, see the man pages of these commands and of the listxattr and getxattr system calls.

Examples

Enable the raw-track access mode of DASD device 0.0.7000 and set the device online afterward:
```
# chccwdev -a raw_track_access=1 -e 0.0.7000
```
Mount the partitioned data set on the DASDs represented by the file nodes /dev/dasde and /dev/dasdf at /mnt:
```
# zdsfs /dev/dasde /dev/dasdf /mnt
```

As user myuser, mount the partitioned data set on the DASD represented by the file node /dev/dasde at /home/myuser/mntzos:

Access the mounted file system exclusively:
```
# zdsfs /dev/dasde /home/myuser/mntzos
```
Allow the root user to access the mounted file system:
```
# zdsfs -o allow_root /dev/dasde /home/myuser/mntzos
```

The ls command does not reflect these permissions. In both cases, it shows:

# ls -al /home/myuser/mntzos
total 121284
dr-xr-x--- 2 root   root          0 Dec  3 15:54 .
drwx------ 3 myuser myuser     4096 Dec  3 15:51 ..
-r--r----- 1 root   root    2833200 Jun 27  2012 EXPORT.BIN1.DAT
-r--r----- 1 root   root    2833200 Jun 27  2012 EXPORT.BIN2.DAT
-r--r----- 1 root   root    2833200 Jun 27  2012 EXPORT.BIN3.DAT
-r--r----- 1 root   root    2833200 Feb 14  2013 EXPORT.BIN4.DAT
dr-xr-x--- 2 root   root   13599360 Aug  9  2012 EXPORT.PDS1.DAT
dr-xr-x--- 2 root   root   13599360 Aug  9  2012 EXPORT.PDS2.DAT
dr-xr-x--- 2 root   root   13599360 Aug  9  2012 EXPORT.PDS3.DAT
dr-xr-x--- 2 root   root   55247400 Aug  9  2012 EXPORT.PDS4.DAT
-r--r----- 1 root   root        981 Dec  3 15:54 metadata.txt

$ ls -al /dev/dasde
brw-rw---- 1 root disk 94, 16 Dec  3 13:58 /dev/dasde

As root user, mount the partitioned data set on the DASD represented by the file node /dev/dasde at /mnt on behalf of the user ID myuser (UID=1002), and permit the members of the group ID zosimport (GID=1002) file access:

# zdsfs /dev/dasde /mnt -o uid=1002,gid=1002,allow_other,default_permissions

The ls command indicates the owner myuser and the access right for group zosimport:

$ ls -al /mnt
total 121284
dr-xr-x---  2 myuser zosimport        0 Dec  3 14:22 .
drwxr-xr-x 23 root   root          4096 Dec  3 13:59 ..
-r--r-----  1 myuser zosimport      981 Dec  3 14:22 metadata.txt
-r--r-----  1 myuser zosimport  2833200 Jun 27  2012 EXPORT.BIN1.DAT
-r--r-----  1 myuser zosimport  2833200 Jun 27  2012 EXPORT.BIN2.DAT
-r--r-----  1 myuser zosimport  2833200 Feb 14  2013 EXPORT.BIN3.DAT
-r--r-----  1 myuser zosimport  2833200 Jun 27  2012 EXPORT.BIN4.DAT
dr-xr-x---  2 myuser zosimport 13599360 Aug  9  2012 EXPORT.PDS1.DAT
dr-xr-x---  2 myuser zosimport 13599360 Aug  9  2012 EXPORT.PDS2.DAT
dr-xr-x---  2 myuser zosimport 55247400 Aug  9  2012 EXPORT.PDS3.DAT
dr-xr-x---  2 myuser zosimport 13599360 Aug  9  2012 EXPORT.PDS4.DAT

Unmount the partitioned data set that is mounted at /mnt:
```
# fusermount -u /mnt
```
Show the extended attributes of a file, FB.XMP.TXT, on a z/OS DASD that is mounted on /mnt:
```
# getfattr -d /mnt/FB.XMP.TXT
```
Show the extended attributes of all files on a z/OS DASD that is mounted on /mnt:
```
# cat /mnt/metadata.txt
```