mount_umap(8) [netbsd man page]
MOUNT_UMAP(8) BSD System Manager's Manual MOUNT_UMAP(8) NAME
mount_umap -- user and group ID remapping file system layer SYNOPSIS
mount_umap [-o options] -g gid-mapfile -u uid-mapfile target mount-point DESCRIPTION
The mount_umap command is used to mount a sub-tree of an existing file system that uses a different set of uids and gids than the local sys- tem. Such a file system could be mounted from a remote site via NFS, a local file system on removable media brought from some foreign loca- tion that uses a different user/group database, or could be a local file system for another operating system which does not support Unix- style user/group IDs, or which uses a different numbering scheme. Both target and mount-point are converted to absolute paths before use. The options are as follows: -g gid-mapfile Use the group ID mapping specified in gid-mapfile. This flag is required. -o Options are specified with a -o flag followed by a comma separated string of options. See the mount(8) man page for possible options and their meanings. -u uid-mapfile Use the user ID mapping specified in uid-mapfile. This flag is required. The mount_umap command uses a set of files provided by the user to make correspondences between uids and gids in the sub-tree's original environment and some other set of ids in the local environment. For instance, user smith might have uid 1000 in the original environment, while having uid 2000 in the local environment. The mount_umap command allows the subtree from smith's original environment to be mapped in such a way that all files with owning uid 1000 look like they are actually owned by uid 2000. target should be the current location of the sub-tree in the local system's name space. mount-point should be a directory where the mapped subtree is to be placed. uid-mapfile and gid-mapfile describe the mappings to be made between identifiers. The format of the user and group ID mapping files is very simple. The first line of the file is the total number of mappings present in the file. The remaining lines each consist of two numbers: the ID in the mapped subtree and the ID in the original subtree. For example, to map uid 1000 in the original subtree to uid 2000 in the mapped subtree: 1 2000 1000 For user IDs in the original subtree for which no mapping exists, the user ID will be mapped to the user ``nobody''. For group IDs in the original subtree for which no mapping exists, the group ID will be mapped to the group ``nobody''. There is a limit of 64 user ID mappings and 16 group ID mappings. The mapfiles can be located anywhere in the file hierarchy, but they must be owned by root, and they must be writable only by root. mount_umap will refuse to map the sub-tree if the ownership or permissions on these files are improper. It will also report an error if the count of mappings in the first line of the map files is not correct. SEE ALSO
mount(8), mount_null(8) HISTORY
The mount_umap utility first appeared in 4.4BSD. BUGS
The implementation is not very sophisticated. BSD
March 6, 2001 BSD
Check Out this Related Man Page
cddevsuppl(8) System Manager's Manual cddevsuppl(8) NAME
cddevsuppl - Sets and gets the major and minor numbers of a device file on a Rock Ridge format CD-ROM SYNOPSIS
/usr/sbin/cddevsuppl -m mapfile [-c] /usr/sbin/cddevsuppl -u unmapfile [-c] /usr/sbin/cddevsuppl [-c] OPTIONS
Directs cddevsuppl to continue processing the device file mappings if an error is returned for a specific device file mapping. An error message for that specific device file will be printed to standard error. The default action is to stop processing when an error has occurred. This option is useful only when used in combination with the -m mapfile or -u unmapfile options. Maps the major and minor num- bers for device files. The mappings are specified in mapfile. This text file has one entry for each device file mapping in the format: device_file_path new_major new_minor The device_file_path field is the full pathname of the file on the CD-ROM, and the new_major and new_minor fields are integers. The fields are separated by white space. The entries are separated by newlines. Anything beyond the third field is ignored. The follow- ing is an example of mapfile: /mnt/dev/ttys4 8 2050 /mnt/dev/zero 38 0 The maximum number of mappings for a Rock Ridge compact disk is defined in the header file <sys/cdrom.h>. If a device file is mapped again, the previous device file mapping for the device file is overridden. Unmaps the major and minor numbers for device files. The mappings are specified in unmapfile. This text file has one entry for each device file mapping in the format: device_file_path The device_file_path field is the full pathname of the file on the CD-ROM. The entries are separated by newlines. Anything beyond the first field is ignored. The following is an example of mapfile: /mnt/dev/zero DESCRIPTION
The cddevsuppl command is used to map and unmap the major and minor numbers of a device file on a mounted Rock Ridge format CD-ROM. The -m mapfile option maps the major and minor number of device files and displays the new setting, if the mapping is successful. This option is used to add new mappings or to change existing mappings, in case the major and minor numbers of the device files are incorrect. The -u unmapfile option removes the existing mappings for files specified in unmapfile and displays the device file and the major/minor numbers as recorded on the CD-ROM. If no options are used, the cddevsuppl command displays the existing device file mappings. If the mapping table is empty, nothing is dis- played. Note: The mapping table is cleared after a mount or umount command. If you want to open a device file on a CD-ROM, the dev option must be specified in the mount command. See mount(8) for more information. RESTRICTIONS
Only the superuser can change administrative CD-ROM features successfully. To read the current device file mappings, the user must have read permission on the device file. Mappings should be established before affected device files are used. If the command is applied for device file mappings when device files have already been opened, the effect of this command on these files is undefined. Only existing devices files on the CD-ROM can be mapped. These files are indicated by the mode: b (block special file) or c (character spe- cial file). Use the ls -l command to display the file modes.. If you access device files on a CD-ROM that are mapped to inappropriate major and minor numbers, undefined results can occur. The device file mappings for a mounted CD-ROM are eliminated when the CD-ROM is unmounted. The cddevsuppl(8) command is not supported in a TruCluster Server environment. EXIT STATUS
The following exit values are returned: Successful completion. File not found, file is not a file or directory within a CD-ROM file hier- archy, or access denied. Not user with appropriate privileges. Too many mappings. Parameter error or bad format in a mapping file. File is not a device file. File not previously mapped. EXAMPLES
The following example shows the output of the cddevsuppl command when no CD-ROM is mounted and no files are mapped: # cddevsuppl # The fol- lowing example shows the output of the cddevsuppl command after a CD-ROM file system has been mounted: # /usr/sbin/mount -t cdfs -o nover- sion,rrip,dev /dev/disk/cdrom0c /mnt # cddevsuppl # The following example maps the major and minor numbers of files mounted in the previous example and specified in mapfile. Note: If you want, you can issue an ls -l command before and after the cddevsuppl command to verify that the major and minor numbers have changed. # cddevsuppl -m /tmp/mapfile /mnt/dev/ttys4: (8,2050) /mnt/dev/zero: (38,0) The following exam- ple unmaps the major and minor numbers of the file specified in unmapfile file and shows the result of the subsequent cddevsuppl command: # cddevsuppl -u /tmp/unmapfile /mnt/dev/zero: (1,5) # cddevsuppl /mnt/dev/ttys4: (8,2050) The following example unmounts the /mnt file system and shows the output of the subsequent cddevsuppl command: # umount /mnt # cddevsuppl # SEE ALSO
Commands: mount(8) Files: cdfs(4) Functions: cd_setdevmap(3), cd_getdevmap(3) cddevsuppl(8)