umview - User Mode implementation of View-OS
The main goal of the View-OS project is to give each process its
own view of the system resources. For example, each process can mount
filesystems or hide some file or directories. It is also possible to assign
virtual network interfaces, IP addresses or define virtual devices for each
process (or for hierarchies of processes).
umview is the user mode implementation of View-OS concepts. It is a
modular partial virtual machine. umview before loading any module is
completely transparent, a process behaves inside umview as it would
have behaved outside. Each module can customize specific entities: there are
modules to mount filesystems at user-level (umfuse) , to define
virtual network interfaces (lwipv6) , to define virtual devices
(umdev) , to provide interpreters for executables, e.g. to support
executables for foreign architectures (umbinfmt) , to hide, move,
overlay parts of the file system (viewfs).
These are some examples of modules provided by the View-OS team. umview
aims to provide a general interface to customize the system call semantics
of process under specified conditions. So more modules will be added both by
the View-OS team and by third parties.
- -V name
- --viewname
name
- set the name of the view. The view can be read and set using vuname
or viewname commands.
- -p module [ ,
module_options ]
- --preload
module [ , module_options ]
- preload modules. Modules will be loaded as shared libraries thus all the
rules to load libraries apply. Modules must be loaded from a directory
within the ld.so search path or should be specified by their pathnames. If
necessary configure the LD_LIBRARY_PATH environment variable
appropriately. module_options are module specific configuration
options, thus the reader should refer to each service module manual for a
complete description. Modules can be loaded at run time using the
um_add_service command.
- -s
- --secure
- set kmview in human mode, i.e. force the check of capabilities and
permissions. uid is 0 at startup, in this way it is possible to load
modules and mount services. When a process sets its uid as an unprivileged
user (via setuid(2) or viewsu(1)), capability and permissions are
enforced.
- -f rcfile
- --rc rcfile
- Use rcfile as the initialization file for kmview. kmview always
executes /etc/viewosrc if exists, then kmview executes the
initialization file set by this option or ~/.viewosrc.
- -x
- --nonesting
- umview is able to provide module nesting, i.e. a module can provide
services on the basis of virtual services provided by another module or
even by the module itself. For example it is possible to mount a file
system image which is stored in an already virtually mounted filesystem.
This feature requires the pure_libc library. The -x or
--nonesting option disables the nesting feature.
- -n
- --nokernelpatch
- umview is able to use some specific kernel extensions (when
present) to increase its performance. The source distribution of
umview include the kernel patches for the latest kernels. The
kernel extensions are enabled by default when available. This option
disables the kernel extensions.
- --nokmulti
- This option disables the PTRACE_MULTI kernel extension.
- --noksysvm
- This option disables the PTRACE_SYSVM kernel extension.
- --nokviewos
- This option disables the PTRACE_SYSVIEWOS kernel extension (already
experimental, not yet released).
- -o file
- --output
file
- This option diverts the debugging output to the file specified, it is
useful when umview has been compiled with debugging
extensions.
- -v
- --version
- Print the version and exit.
- -h
- --help
- Print a short help message and exit.
View-OS is a project of the Computer Science Department,
University of Bologna. Project Leader: Renzo Davoli. Development Team: P.
Angelelli, A. Bacchelli, M. Belletti, P. Beverini, D. Billi, A. Forni, L.
Gardenghi, A. Gasparini, D. Lacamera, C. Martellini, A. Seraghiti
<http://www.sourceforge.net/projects/view-os>
Howto's and further information can be found on the project wiki
<wiki.virtualsquare.org>.