|
|
|
|
@ -1,19 +1,25 @@
|
|
|
|
|
@node System Information, System Configuration, Users and Groups, Top
|
|
|
|
|
@c %MENU% Getting information about the hardware and operating system
|
|
|
|
|
@chapter System Information
|
|
|
|
|
@node System Management, System Configuration, Users and Groups, Top
|
|
|
|
|
@c %MENU% Controlling the system and getting information about it
|
|
|
|
|
@chapter System Management
|
|
|
|
|
|
|
|
|
|
This chapter describes facilities for controlling the system that
|
|
|
|
|
underlies a process (including the operating system and hardware) and
|
|
|
|
|
for getting information about it. Anyone can generally use the
|
|
|
|
|
informational facilities, but usually only a properly privileged process
|
|
|
|
|
can make changes.
|
|
|
|
|
|
|
|
|
|
This chapter describes functions that return information about the
|
|
|
|
|
particular machine that is in use---the type of hardware, the type of
|
|
|
|
|
software, and the individual machine's name.
|
|
|
|
|
|
|
|
|
|
@menu
|
|
|
|
|
* Host Identification:: Determining the name of the machine.
|
|
|
|
|
* Hardware/Software Type ID:: Determining the hardware type of the
|
|
|
|
|
machine and what operating system it is
|
|
|
|
|
running.
|
|
|
|
|
* Filesystem handling:: Which is mounted and/or available?
|
|
|
|
|
* Filesystem Handling:: Controlling/querying mounts
|
|
|
|
|
@end menu
|
|
|
|
|
|
|
|
|
|
To get information on parameters of the system that are built into the
|
|
|
|
|
system, such as the maximum length of a filename, @ref{System
|
|
|
|
|
Configuration}.
|
|
|
|
|
|
|
|
|
|
@node Host Identification
|
|
|
|
|
@section Host Identification
|
|
|
|
|
@ -182,15 +188,45 @@ possibility.
|
|
|
|
|
@end deftypefun
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
@node Filesystem handling
|
|
|
|
|
@section Which filesystems are mounted and/or available?
|
|
|
|
|
@node Filesystem Handling
|
|
|
|
|
@section Controlling/querying mounts
|
|
|
|
|
|
|
|
|
|
The Unix concept of @emph{Everything is a file} is based on the
|
|
|
|
|
ability to @dfn{mount} filesystems or other things into the
|
|
|
|
|
filesystem. For some programs it is desirable and necessary to access
|
|
|
|
|
information about whether a certain filesystem is mounted and, if it is,
|
|
|
|
|
where, or simply to get lists of all the available filesystems. The
|
|
|
|
|
GNU libc provides some functions to retrieve this information portably.
|
|
|
|
|
All files are in filesystems, and before you can access any file, its
|
|
|
|
|
filesystem must be mounted. Because of Unix's concept of
|
|
|
|
|
@emph{Everything is a file}, mounting of filesystems is central to doing
|
|
|
|
|
almost anything. This section explains how to find out what filesystems
|
|
|
|
|
are currently mounted and what filesystems are available for mounting,
|
|
|
|
|
and how to change what is mounted.
|
|
|
|
|
|
|
|
|
|
The classic filesystem is the contents of a disk drive. The concept is
|
|
|
|
|
considerably more abstract, though, and lots of things other than disk
|
|
|
|
|
drives can be mounted.
|
|
|
|
|
|
|
|
|
|
Some block devices don't correspond to traditional devices like disk
|
|
|
|
|
drives. For example, a loop device is a block device whose driver uses
|
|
|
|
|
a regular file in another filesystem as its medium. So if that regular
|
|
|
|
|
file contains appropriate data for a filesystem, you can by mounting the
|
|
|
|
|
loop device essentially mount a regular file.
|
|
|
|
|
|
|
|
|
|
Some filesystems aren't based on a device of any kind. The ``proc''
|
|
|
|
|
filesystem, for example, contains files whose data is made up by the
|
|
|
|
|
filesystem driver on the fly whenever you ask for it. And when you
|
|
|
|
|
write to it, the data you write causes changes in the system. No data
|
|
|
|
|
gets stored.
|
|
|
|
|
|
|
|
|
|
@c It would be good to mention NFS mounts here.
|
|
|
|
|
|
|
|
|
|
@menu
|
|
|
|
|
* Mount Information:: What is or could be mounted?
|
|
|
|
|
* Mount/Unmount/Remount:: Controlling what is mounted and how
|
|
|
|
|
@end menu
|
|
|
|
|
|
|
|
|
|
@node Mount Information, Mount/Unmount/Remount, , Filesystem Handling
|
|
|
|
|
|
|
|
|
|
For some programs it is desirable and necessary to access information
|
|
|
|
|
about whether a certain filesystem is mounted and, if it is, where, or
|
|
|
|
|
simply to get lists of all the available filesystems. The GNU libc
|
|
|
|
|
provides some functions to retrieve this information portably.
|
|
|
|
|
|
|
|
|
|
Traditionally Unix systems have a file named @file{/etc/fstab} which
|
|
|
|
|
describes all possibly mounted filesystems. The @code{mount} program
|
|
|
|
|
@ -203,6 +239,13 @@ functions described in this section can do this and they also provide
|
|
|
|
|
the functionality to convert the external textual representation to the
|
|
|
|
|
internal representation.
|
|
|
|
|
|
|
|
|
|
Note that the @file{fstab} and @file{mtab} files are maintained on a
|
|
|
|
|
system by @emph{convention}. It is possible for the files not to exist
|
|
|
|
|
or not to be consistent with what is really mounted or available to
|
|
|
|
|
mount, if the system's administration policy allows it. But programs
|
|
|
|
|
that mount and unmount filesystems typically maintain and use these
|
|
|
|
|
files as described herein.
|
|
|
|
|
|
|
|
|
|
@vindex _PATH_FSTAB
|
|
|
|
|
@vindex _PATH_MNTTAB
|
|
|
|
|
@vindex FSTAB
|
|
|
|
|
@ -215,6 +258,15 @@ defined in @file{fstab.h} and @code{_PATH_MNTTAB}, defined in
|
|
|
|
|
deprecated and kept only for backward compatibility. The two former
|
|
|
|
|
names should always be used.
|
|
|
|
|
|
|
|
|
|
@menu
|
|
|
|
|
* fstab:: The @file{fstab} file
|
|
|
|
|
* mtab:: The @file{mtab} file
|
|
|
|
|
* Other Mount Information:: Other (non-libc) sources of mount information
|
|
|
|
|
@end menu
|
|
|
|
|
|
|
|
|
|
@node fstab
|
|
|
|
|
@subsection The @file{fstab} file
|
|
|
|
|
|
|
|
|
|
The internal representation for entries of the file is @w{@code{struct
|
|
|
|
|
fstab}}, defined in @file{fstab.h}.
|
|
|
|
|
|
|
|
|
|
@ -363,11 +415,12 @@ function is not thread-safe. If an error occurred @code{getfsent}
|
|
|
|
|
returns a @code{NULL} pointer.
|
|
|
|
|
@end deftypefun
|
|
|
|
|
|
|
|
|
|
To access the @file{mtab} file there is a different set of functions and
|
|
|
|
|
also a different structure to describe the results.
|
|
|
|
|
|
|
|
|
|
@node mtab
|
|
|
|
|
@subsection The @file{mtab} file
|
|
|
|
|
The following functions and data structure access the @file{mtab} file.
|
|
|
|
|
|
|
|
|
|
@comment fstab.h
|
|
|
|
|
@comment mntent.h
|
|
|
|
|
@comment BSD
|
|
|
|
|
@deftp {Data Type} {struct mntent}
|
|
|
|
|
This structure is used with the @code{getmntent}, @code{getmntent_t},
|
|
|
|
|
@ -572,3 +625,300 @@ This function is useful to test whether a specific option is present but
|
|
|
|
|
when all options have to be processed one is better off with using the
|
|
|
|
|
@code{getsubopt} function to iterate over all options in the string.
|
|
|
|
|
@end deftypefun
|
|
|
|
|
|
|
|
|
|
@node Other Mount Information
|
|
|
|
|
@subsection Other (Non-libc) Sources of Mount Information
|
|
|
|
|
|
|
|
|
|
On a system with a Linux kernel and the @code{proc} filesystem, you can
|
|
|
|
|
get information on currently mounted filesystems from the file
|
|
|
|
|
@file{mounts} in the @code{proc} filesystem. Its format is similar to
|
|
|
|
|
that of the @file{mtab} file, but represents what is truly mounted
|
|
|
|
|
without relying on facilities outside the kernel to keep @file{mtab} up
|
|
|
|
|
to date.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
@node Mount/Unmount/Remount, , Mount Information, Filesystem Handling
|
|
|
|
|
|
|
|
|
|
This section describes the functions for mounting, unmounting, and
|
|
|
|
|
remounting filesystems.
|
|
|
|
|
|
|
|
|
|
Only the superuser can mount, unmount, or remount a filesystem.
|
|
|
|
|
|
|
|
|
|
These functions do not access the @file{fstab} and @file{mtab} files. You
|
|
|
|
|
should maintain and use these separately. @xref{Mount Information}.
|
|
|
|
|
|
|
|
|
|
The symbols in this section are declared in @file{sys/mount.h}.
|
|
|
|
|
|
|
|
|
|
@comment sys/mount.h
|
|
|
|
|
@deftypefun {int} mount (const char *@var{special_file}, const char *@var{dir}, const char *@var{fstype}, unsigned long int @var{options}, const void *@var{data})
|
|
|
|
|
|
|
|
|
|
@code{mount} mounts or remounts a filesystem. The two operations are
|
|
|
|
|
quite different and are merged rather unnnaturally into this one function.
|
|
|
|
|
The @code{MS_REMOUNT} option, explained below, determines whether
|
|
|
|
|
@code{mount} mounts or remounts.
|
|
|
|
|
|
|
|
|
|
For a mount, the filesystem on the block device represented by the
|
|
|
|
|
device special file named @var{special_file} gets mounted over the mount
|
|
|
|
|
point @var{dir}. This means that the directory @var{dir} (along with any
|
|
|
|
|
files in it) is no longer visible; in its place (and still with the name
|
|
|
|
|
@var{dir}) is the root directory of the filesystem on the device.
|
|
|
|
|
|
|
|
|
|
As an exception, if the filesystem type (see below) is one which is not
|
|
|
|
|
based on a device (e.g. ``proc''), @code{mount} instantiates a
|
|
|
|
|
filesystem and mounts it over @var{dir} and ignores @var{special_file}.
|
|
|
|
|
|
|
|
|
|
For a remount, @var{dir} specifies the mount point where the filesystem
|
|
|
|
|
to be remounted is (and remains) mounted and @var{special_file} is
|
|
|
|
|
ignored. Remounting a filesystem means changing the options that control
|
|
|
|
|
operations on the filesystem while it is mounted. It does not mean
|
|
|
|
|
unmounting and mounting again.
|
|
|
|
|
|
|
|
|
|
For a mount, you must identify the type of the filesystem as
|
|
|
|
|
@var{fstype}. This type tells the kernel how to access the filesystem
|
|
|
|
|
and can be thought of as the name of a filesystem driver. The
|
|
|
|
|
acceptable values are system dependent. On a system with a Linux kernel
|
|
|
|
|
and the @code{proc} filesystem, the list of possible values is in the
|
|
|
|
|
file @file{filesystems} in the @code{proc} filesystem (e.g. type
|
|
|
|
|
@kbd{cat /proc/filesystems} to see the list). With a Linux kernel, the
|
|
|
|
|
types of filesystems that @code{mount} can mount, and their type names,
|
|
|
|
|
depends on what filesystem drivers are configured into the kernel or
|
|
|
|
|
loaded as loadable kernel modules. An example of a common value for
|
|
|
|
|
@var{fstype} is @code{ext2}.
|
|
|
|
|
|
|
|
|
|
For a remount, @code{mount} ignores @var{fstype}.
|
|
|
|
|
|
|
|
|
|
@c This is traditionally called "rwflag" for historical reasons.
|
|
|
|
|
@c No point in confusing people today, though.
|
|
|
|
|
@var{options} specifies a variety of options that apply until the
|
|
|
|
|
filesystem in unmounted or remounted. The precise meaning of an option
|
|
|
|
|
depends on the filesystem and with some filesystems, an option may have
|
|
|
|
|
no effect at all. Furthermore, for some filesystems, some of these
|
|
|
|
|
options (but never @code{MS_RDONLY}) can be overridden for individual
|
|
|
|
|
file accesses via @code{ioctl}.
|
|
|
|
|
|
|
|
|
|
@var{options} is a bit string with bit fields defined using the
|
|
|
|
|
following mask and masked value macros:
|
|
|
|
|
|
|
|
|
|
@table @code
|
|
|
|
|
@item MS_MGC_MASK
|
|
|
|
|
This multibit field contains a magic number. If it does not have the value
|
|
|
|
|
@code{MS_MGC_VAL}, @code{mount} assumes all the following bits are zero and
|
|
|
|
|
the @var{data} argument is a null string, regardless of their actual values.
|
|
|
|
|
|
|
|
|
|
@item MS_REMOUNT
|
|
|
|
|
This bit on means to remount the filesystem. Off means to mount it.
|
|
|
|
|
@c There is a mask MS_RMT_MASK in mount.h that says only two of the options
|
|
|
|
|
@c can be reset by remount. But the Linux kernel has it's own version of
|
|
|
|
|
@c MS_RMT_MASK that says they all can be reset. As far as I can tell,
|
|
|
|
|
@c libc just passes the arguments straight through to the kernel.
|
|
|
|
|
|
|
|
|
|
@item MS_RDONLY
|
|
|
|
|
This bit on specifies that no writing to the filesystem shall be allowed
|
|
|
|
|
while it is mounted. This cannot be overridden by @code{ioctl}. This
|
|
|
|
|
option is available on nearly all filesystems.
|
|
|
|
|
|
|
|
|
|
@item S_IMMUTABLE
|
|
|
|
|
This bit on specifies that no writing to the files in the filesystem
|
|
|
|
|
shall be allowed while it is mounted. This can be overridden for a
|
|
|
|
|
particular file access by a properly privileged call to @code{ioctl}.
|
|
|
|
|
This option is a relatively new invention and is not available on many
|
|
|
|
|
filesystems.
|
|
|
|
|
|
|
|
|
|
@item S_APPEND
|
|
|
|
|
This bit on specifies that the only file writing that shall be allowed
|
|
|
|
|
while the filesystem is mounted is appending. Some filesystems allow
|
|
|
|
|
this to be overridden for a particular process by a properly privileged
|
|
|
|
|
call to @code{ioctl}. This is a relatively new invention and is not
|
|
|
|
|
available on many filesystems.
|
|
|
|
|
|
|
|
|
|
@item MS_NOSUID
|
|
|
|
|
This bit on specifies that Setuid and Setgid permissions on files in the
|
|
|
|
|
filesystem shall be ignored while it is mounted.
|
|
|
|
|
|
|
|
|
|
@item MS_NOEXEC
|
|
|
|
|
This bit on specifies that no files in the filesystem shall be executed
|
|
|
|
|
while the filesystem is mounted.
|
|
|
|
|
|
|
|
|
|
@item MS_NODEV
|
|
|
|
|
This bit on specifies that no device special files in the filesystem
|
|
|
|
|
shall be accessible while the filesystem is mounted.
|
|
|
|
|
|
|
|
|
|
@item MS_SYNCHRONOUS
|
|
|
|
|
This bit on specifies that all writes to the filesystem while it is
|
|
|
|
|
mounted shall be synchronous; i.e. data shall be synced before each
|
|
|
|
|
write completes rather than held in the buffer cache.
|
|
|
|
|
|
|
|
|
|
@item MS_MANDLOCK
|
|
|
|
|
This bit on specifies that mandatory locks on files shall be permitted while
|
|
|
|
|
the filesystem is mounted.
|
|
|
|
|
|
|
|
|
|
@item MS_NOATIME
|
|
|
|
|
This bit on specifies that access times of files shall not be updated when
|
|
|
|
|
the files are accessed while the filesystem is mounted.
|
|
|
|
|
|
|
|
|
|
@item MS_NODIRATIME
|
|
|
|
|
This bit on specifies that access times of directories shall not be updated
|
|
|
|
|
when the directories are accessed while the filesystem in mounted.
|
|
|
|
|
|
|
|
|
|
@c there is also S_QUOTA Linux fs.h (mount.h still uses its former name
|
|
|
|
|
@c S_WRITE), but I can't see what it does. Turns on quotas, I guess.
|
|
|
|
|
|
|
|
|
|
@end table
|
|
|
|
|
|
|
|
|
|
Any bits not covered by the above masks should be set off; otherwise,
|
|
|
|
|
results are undefined.
|
|
|
|
|
|
|
|
|
|
The meaning of @var{data} depends on the filesystem type and is controlled
|
|
|
|
|
entirely by the filesystem driver in the kernel.
|
|
|
|
|
|
|
|
|
|
Example:
|
|
|
|
|
|
|
|
|
|
@smallexample
|
|
|
|
|
@group
|
|
|
|
|
#include <sys/mount.h>
|
|
|
|
|
|
|
|
|
|
mount("/dev/hdb", "/cdrom", MS_MGC_VAL | MS_RDONLY | MS_NOSUID, "");
|
|
|
|
|
|
|
|
|
|
mount("/dev/hda2", "/mnt", MS_MGC_VAL | MS_REMOUNT, "");
|
|
|
|
|
|
|
|
|
|
@end group
|
|
|
|
|
@end smallexample
|
|
|
|
|
|
|
|
|
|
Appropriate arguments for @code{mount} are conventionally recorded in
|
|
|
|
|
the @file{fstab} table. @xref{Mount Information}.
|
|
|
|
|
|
|
|
|
|
The return value is zero if the mount or remount is successful. Otherwise,
|
|
|
|
|
it is @code{-1} and @code{errno} is set appropriately. The values of
|
|
|
|
|
@code{errno} are filesystem dependent, but here is a general list:
|
|
|
|
|
|
|
|
|
|
@table @code
|
|
|
|
|
@item EPERM
|
|
|
|
|
The process is not superuser.
|
|
|
|
|
@item ENODEV
|
|
|
|
|
The file system type @var{fstype} is not known to the kernel.
|
|
|
|
|
@item ENOTBLK
|
|
|
|
|
The file @var{dev} is not a block device special file.
|
|
|
|
|
@item EBUSY
|
|
|
|
|
|
|
|
|
|
@itemize
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
The device is already mounted.
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
The mount point is busy. (E.g. it is some process' working directory or
|
|
|
|
|
has a filesystem mounted on it already).
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
The request is to remount read-only, but there are files open for write.
|
|
|
|
|
@end itemize
|
|
|
|
|
|
|
|
|
|
@item EINVAL
|
|
|
|
|
@itemize
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
A remount was attempted, but there is no filesystem mounted over the
|
|
|
|
|
specified mount point.
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
The supposed filesystem has an invalid superblock.
|
|
|
|
|
|
|
|
|
|
@end itemize
|
|
|
|
|
|
|
|
|
|
@item EACCESS
|
|
|
|
|
@itemize
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
The filesystem is inherently read-only (possibly due to a switch on the
|
|
|
|
|
device) and the process attempted to mount it read/write (by setting the
|
|
|
|
|
@code{MS_RDONLY} bit off).
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
@var{special_file} or @var{dir} is not accessible due to file permissions.
|
|
|
|
|
|
|
|
|
|
@item
|
|
|
|
|
@var{special_file} is not accessible because it is in a filesystem that is
|
|
|
|
|
mounted with the @code{MS_NODEV} option.
|
|
|
|
|
|
|
|
|
|
@end itemize
|
|
|
|
|
|
|
|
|
|
@item EM_FILE
|
|
|
|
|
The table of dummy devices is full. @code{mount} needs to create a
|
|
|
|
|
dummy device (aka ``unnamed'' device) if the filesystem being mounted is
|
|
|
|
|
not one that uses a device.
|
|
|
|
|
|
|
|
|
|
@end table
|
|
|
|
|
|
|
|
|
|
@end deftypefun
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
@comment sys/mount.h
|
|
|
|
|
@deftypefun {int} umount2 (const char *@var{file}, int @var{flags})
|
|
|
|
|
|
|
|
|
|
@code{umount2} unmounts a filesystem.
|
|
|
|
|
|
|
|
|
|
You can identify the filesystem to unmount either by the device special
|
|
|
|
|
file that contains the filesystem or by the mount point. The effect is
|
|
|
|
|
the same. Specify either as the string @var{file}.
|
|
|
|
|
|
|
|
|
|
@var{flags} contains the one-bit field identified by the following
|
|
|
|
|
mask macro:
|
|
|
|
|
|
|
|
|
|
@table @code
|
|
|
|
|
|
|
|
|
|
@item MNT_FORCE
|
|
|
|
|
This bit on means to force the unmounting even if the filesystem is
|
|
|
|
|
busy, by making it unbusy first. If the bit is off and the filesystem is
|
|
|
|
|
busy, @code{umount2} fails with @code{errno} = @code{EBUSY}. Depending
|
|
|
|
|
on the filesystem, this may override all, some, or no busy conditions.
|
|
|
|
|
|
|
|
|
|
@end table
|
|
|
|
|
|
|
|
|
|
All other bits in @var{flags} should be set to zero; otherwise, the result
|
|
|
|
|
is undefined.
|
|
|
|
|
|
|
|
|
|
Example:
|
|
|
|
|
|
|
|
|
|
@smallexample
|
|
|
|
|
@group
|
|
|
|
|
#include <sys/mount.h>
|
|
|
|
|
|
|
|
|
|
umount2("/mnt", MNT_FORCE);
|
|
|
|
|
|
|
|
|
|
umount2("/dev/hdd1", 0);
|
|
|
|
|
|
|
|
|
|
@end group
|
|
|
|
|
@end smallexample
|
|
|
|
|
|
|
|
|
|
After the filesystem is unmounted, the directory that was the mount point
|
|
|
|
|
is visible, as are any files in it.
|
|
|
|
|
|
|
|
|
|
As part of unmounting, @code{umount2} syncs the filesystem.
|
|
|
|
|
|
|
|
|
|
If the unmounting is successful, the return value is zero. Otherwise, it
|
|
|
|
|
is @code{-1} and @code{errno} is set accordingly:
|
|
|
|
|
|
|
|
|
|
@table @code
|
|
|
|
|
@item EPERM
|
|
|
|
|
The process is not superuser.
|
|
|
|
|
@item EBUSY
|
|
|
|
|
The filesystem cannot be unmounted because it is busy. E.g. it contains
|
|
|
|
|
a directory that is some process's working directory or a file that some
|
|
|
|
|
process has open. With some filesystems in some cases, you can avoid
|
|
|
|
|
this failure with the @code{MNT_FORCE} option.
|
|
|
|
|
|
|
|
|
|
@item EINVAL
|
|
|
|
|
@var{file} validly refers to a file, but that file is neither a mount
|
|
|
|
|
point nor a device special file of a currently mounted filesystem.
|
|
|
|
|
|
|
|
|
|
@end table
|
|
|
|
|
@end deftypefun
|
|
|
|
|
|
|
|
|
|
@comment sys/mount.h
|
|
|
|
|
@deftypefun {int} umount (const char *@var{file})
|
|
|
|
|
|
|
|
|
|
@code{umount} does the same thing as @code{umount2} with @var{flags}
|
|
|
|
|
set to zeroes. It exists for compatibility.
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
@end deftypefun
|
|
|
|
|
|
Ulrich Drepper