CedarBackup3.writers.util

Provides utilities related to image writers. :author: Kenneth J. Pronovici <pronovic@ieee.org>

Module Contents

CedarBackup3.writers.util.logger
CedarBackup3.writers.util.MKISOFS_COMMAND = ['mkisofs']
CedarBackup3.writers.util.VOLNAME_COMMAND = ['volname']
CedarBackup3.writers.util.validateDevice(device, unittest=False)

Validates a configured device. The device must be an absolute path, must exist, and must be writable. The unittest flag turns off validation of the device on disk. :param device: Filesystem device path :param unittest: Indicates whether we’re unit testing

Returns

Device as a string, for instance "/dev/cdrw"

Raises

  • ValueError – If the device value is invalid

  • ValueError – If some path cannot be encoded properly

CedarBackup3.writers.util.validateScsiId(scsiId)

Validates a SCSI id string. SCSI id must be a string in the form [<method>:]scsibus,target,lun. For Mac OS X (Darwin), we also accept the form IO.*Services[/N]. Note: For consistency, if None is passed in, None will be returned. :param scsiId: SCSI id for the device

Returns

SCSI id as a string, for instance "ATA:1,0,0"

Raises

ValueError – If the SCSI id string is invalid

CedarBackup3.writers.util.validateDriveSpeed(driveSpeed)

Validates a drive speed value. Drive speed must be an integer which is >= 1. Note: For consistency, if None is passed in, None will be returned. :param driveSpeed: Speed at which the drive writes

Returns

Drive speed as an integer

Raises

ValueError – If the drive speed value is invalid

CedarBackup3.writers.util.readMediaLabel(devicePath)

Reads the media label (volume name) from the indicated device. The volume name is read using the volname command. :param devicePath: Device path to read from

Returns

Media label as a string, or None if there is no name or it could not be read

class CedarBackup3.writers.util.IsoImage(device=None, boundaries=None, graftPoint=None)

Bases: object

Represents an ISO filesystem image.

Summary

This object represents an ISO 9660 filesystem image. It is implemented in terms of the mkisofs program, which has been ported to many operating systems and platforms. A “sensible subset” of the mkisofs functionality is made available through the public interface, allowing callers to set a variety of basic options such as publisher id, application id, etc. as well as specify exactly which files and directories they want included in their image.

By default, the image is created using the Rock Ridge protocol (using the -r option to mkisofs) because Rock Ridge discs are generally more useful on UN*X filesystems than standard ISO 9660 images. However, callers can fall back to the default mkisofs functionality by setting the useRockRidge instance variable to False. Note, however, that this option is not well-tested.

Where Files and Directories are Placed in the Image

Although this class is implemented in terms of the mkisofs program, its standard “image contents” semantics are slightly different than the original mkisofs semantics. The difference is that files and directories are added to the image with some additional information about their source directory kept intact.

As an example, suppose you add the file /etc/profile to your image and you do not configure a graft point. The file /profile will be created in the image. The behavior for directories is similar. For instance, suppose that you add /etc/X11 to the image and do not configure a graft point. In this case, the directory /X11 will be created in the image, even if the original /etc/X11 directory is empty. I{This behavior differs from the standard mkisofs behavior!}

If a graft point is configured, it will be used to modify the point at which a file or directory is added into an image. Using the examples from above, let’s assume you set a graft point of base when adding /etc/profile and /etc/X11 to your image. In this case, the file /base/profile and the directory /base/X11 would be added to the image.

I feel that this behavior is more consistent than the original mkisofs behavior. However, to be fair, it is not quite as flexible, and some users might not like it. For this reason, the contentsOnly parameter to the addEntry method can be used to revert to the original behavior if desired.

device
boundaries
graftPoint
useRockRidge
applicationId
biblioFile
publisherId
preparerId
volumeId
addEntry(path, graftPoint=None, override=False, contentsOnly=False)

Adds an individual file or directory into the ISO image.

The path must exist and must be a file or a directory. By default, the entry will be placed into the image at the root directory, but this behavior can be overridden using the graftPoint parameter or instance variable.

You can use the contentsOnly behavior to revert to the “original” mkisofs behavior for adding directories, which is to add only the items within the directory, and not the directory itself.

Note: Things get odd if you try to add a directory to an image that will be written to a multisession disc, and the same directory already exists in an earlier session on that disc. Not all of the data gets written. You really wouldn’t want to do this anyway, I guess.

Note: An exception will be thrown if the path has already been added to the image, unless the override parameter is set to True.

Note: The method graftPoints parameter overrides the object-wide instance variable. If neither the method parameter or object-wide value is set, the path will be written at the image root. The graft point behavior is determined by the value which is in effect I{at the time this method is called}, so you must set the object-wide value before calling this method for the first time, or your image may not be consistent.

Note: You cannot use the local graftPoint parameter to “turn off” an object-wide instance variable by setting it to None. Python’s default argument functionality buys us a lot, but it can’t make this method psychic. :)

Parameters

  • path (String representing a path on disk) – File or directory to be added to the image

  • graftPoint (String representing a graft point path, as described above) – Graft point to be used when adding this entry

  • override (Boolean true/false) – Override an existing entry with the same path

  • contentsOnly (Boolean true/false) – Add directory contents only (standard mkisofs behavior)

Raises

  • ValueError – If path is not a file or directory, or does not exist

  • ValueError – If the path has already been added, and override is not set

  • ValueError – If a path cannot be encoded properly

getEstimatedSize()

Returns the estimated size (in bytes) of the ISO image.

This is implemented via the -print-size option to mkisofs, so it might take a bit of time to execute. However, the result is as accurate as we can get, since it takes into account all of the ISO overhead, the true cost of directories in the structure, etc, etc.

Returns

Estimated size of the image, in bytes

Raises

  • IOError – If there is a problem calling mkisofs

  • ValueError – If there are no filesystem entries in the image

writeImage(imagePath)

Writes this image to disk using the image path.

Parameters

imagePath (String representing a path on disk) – Path to write image out as

Raises

  • IOError – If there is an error writing the image to disk

  • ValueError – If there are no filesystem entries in the image

  • ValueError – If a path cannot be encoded properly