Usage¶

There are two basic types of classes in the LogicalFile provider.

Subclasses derived from CIM_LogicalFile represent basic types of files and their system independent properties, such as if the file is readable or its modification time. The classes’ names are self-explanatory. LMI_SymbolicLink represents symbolic link files, LMI_UnixDeviceFile represents unix device files, etc.

The other type of class is LMI_UnixFile. It is used in the Unix-like environment. Its properties are tied to the system – Linux in our case. For example, the group id of the owner or the inode number are among those properties.

To provide ways to connect the file subclasses together, LogicalFile also defines a few associations.

Association classes:

LMI_RootDirectory is used to connect the computer system to its root directory.

LMI_FileIdentity associates the system-independent CIM_LogicalFile subclasses to their respective LMI_UnixFile equivalents that are dependent on the system.

LMI_DirectoryContainsFile serves as a tool to show contents of a directory. Note that directory is usually just a type of file.

Deviations from the schema¶

No classes that represent files have the EnumerateInstances method implemented. The reason for this is that it would be very resource intensive to list all the files on the given filesystem. Even more so, for example, all the symlinks on the filesystem. For that reason, every LogicalFile class implements only its GetInstance method.

The objectpath of the logical file classes consists of these properties:

CSCreationClassName
CSName
FSCreationClassName
FSName
CreationClassName (LFCreationClassName for LMI_UnixFile)
Name (LFName for LMI_UnixFile)

When getting an instance, it’s usually required that all of the key properties are specified. However, it is impossible, or at least needlessly complicated, to know some of them when querying remote machines. For example, if I want to see information about the file ‘/home/user/myfile’ on a remote computer, I don’t want to specify the filesystem it resides on or the type of the file.

Therefore, the only mandatory key properties are CSCreationClassName, CSName and Name (of LFName in case of LMI_UnixFile). FSName, FSCreationClassName and CreationClassName are ignored. They are correctly filled in after the instance has been properly returned.

To have an entry point into the Unix filesystems, an association has been added. It binds the computer system and its root directory. See LMI_RootDirectory.

LMI_UnixFile has been extended to hold additional properties. Currently, those are SELinuxCurrentContext and SELinuxExpectedContext. Should there be need for more additions, this class can be easily extended.

Getting files¶

All further code assumes that a connection object has been created and the default namespace (root/cimv2) is used. Also, the system’s instance must have been acquired.

# plain http connections will likely be refused
c = connect('https://myhost')
# namespace alias for convenience
ns = c.root.cimv2
system = ns.PG_ComputerSystem.first_instance()

Get an instance of the home directory:

name_dict =  {'CSCreationClassName':system.classname,
              'CSName':system.name,
              'CreationClassName':'ignored',
              'FSCreationClassName':'ignored',
              'FSName':'ignored',
              'Name':'/home/jsynacek'}
name = ns.LMI_UnixDirectory.new_instance_name(name_dict)
home = name.to_instance()
print home.Name

Get an instance of a temporary file and see its selinux contexts using the LMI_FileIdentity:

name_dict =  {'CSCreationClassName':system.classname,
              'CSName':system.name,
              'LFCreationClassName':'ignored',
              'FSCreationClassName':'ignored',
              'FSName':'ignored',
              'LFName':'/var/tmp/data_file'}
name = ns.LMI_UnixFile.new_instance_name(name_dict)
unixdata = name.to_instance()
data = unixdata.first_associator(AssocClass='LMI_FileIdentity')
print unixdata.SELinuxCurrentContext
print unixdata.SELinuxExpectedContext
print data.Readable
print data.Writeable
print data.Executable

Get an instance of a symlink and check where it points to:

name_dict =  {'CSCreationClassName':system.classname,
              'CSName':system.name,
              'LFCreationClassName':'ignored',
              'FSCreationClassName':'ignored',
              'FSName':'ignored',
              'LFName':'/home/jsynacek/test-link'}
name = ns.LMI_UnixFile.new_instance_name(name_dict)
unixsymlink = name.to_instance()
symlink = unixsymlink.first_associator(AssocClass='LMI_FileIdentity')
print symlink.TargetFile

Association classes examples¶

List a directory:

files = home.associators(AssocClass='LMI_DirectoryContainsFile')
for f in sorted(files, key=lambda x: x.Name):
    print f.Name

Get the root directory:

root = system.first_associator(AssocClass='LMI_RootDirectory')
print root.Name

Note

For a more complex example of how to use the LogicalFile provider, please refer to the OpenLMI LogicalFile script.