Top Forums Programming read() without changing atime ? Post 302113660 by Perderabo on Sunday 8th of April 2007 08:59:54 PM
Did you miss "Some filesystems have a mount option to inhibit atime updates"? Sometimes I wonder why I bother typing stuff in. Smilie

Well, for those who actually read what I write, Solaris ufs filesystems such as exist on Solaris 8, have such an option and it is mentioned on this page.

By default, the file system is mounted with normal access time (atime) recording. If noatime is specified, the file system will ignore access time updates on files, except when they coincide with updates to the ctime or mtime. See stat(2). This option reduces disk activity on file systems where access times are unimportant (for example, a Usenet news spool).
Test Your Knowledge in Computers #616
Difficulty: Medium
There is no separate char data type in Python.
True or False?

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mount_ufs(1M)						  System Administration Commands					     mount_ufs(1M)

mount_ufs - mount ufs file systems SYNOPSIS
mount -F ufs [generic_options] [-o specific_options] [-O] special | mount_point mount -F ufs [generic_options] [-o specific_options] [-O] special mount_point DESCRIPTION
The mount utility attaches a ufs file system to the file system hierarchy at the mount_point, which is the pathname of a directory. If mount_point has any contents prior to the mount operation, these are hidden until the file system is unmounted. If mount is invoked with special or mount_point as the only arguments, mount will search /etc/vfstab to fill in the missing arguments, including the specific_options. See mount(1M). If special and mount_point are specified without any specific_options, the default is rw. If the directory on which a file system is to be mounted is a symbolic link, the file system is mounted on the directory to which the sym- bolic link refers, rather than on top of the symbolic link itself. OPTIONS
See mount(1M) for the list of supported generic_options. The following options are supported: -o specific_options Specify ufs file system specific options in a comma-separated list with no intervening spaces. If invalid options are specified, a warning message is printed and the invalid options are ignored. The following options are available: dfratime | nodfratime By default, writing access time updates to the disk may be deferred (dfratime) for the file system until the disk is accessed for a reason other than updating access times. nodfratime disables this behavior. If power management is enabled on the system, do not set nodfratime unless noatime is also set. If you set nodfratime without set- ting noatime, the disk is spun up every time a file within a file system on the disk is accessed - even if the file is not modi- fied. forcedirectio | noforcedirectio If forcedirectio is specified and supported by the file system, then for the duration of the mount, forced direct I/O will be used. If the filesystem is mounted using forcedirectio, data is transferred directly between user address space and the disk. If the filesystem is mounted using noforcedirectio, data is buffered in kernel address space when data is transferred between user address space and the disk. forcedirectio is a performance option that is of benefit only in large sequential data transfers. The default behavior is noforcedirectio. global | noglobal If global is specified and supported on the file system, and the system in question is part of a cluster, the file system will be globally visible on all nodes of the cluster. If noglobal is specified, the mount will not be globally visible. The default behav- ior is noglobal. intr | nointr Allow (do not allow) keyboard interrupts to kill a process that is waiting for an operation on a locked file system. The default is intr. largefiles | nolargefiles If nolargefiles is specified and supported by the file system, then for the duration of the mount it is guaranteed that all regular files in the file system have a size that will fit in the smallest object of type off_t supported by the system performing the mount. The mount will fail if there are any files in the file system not meeting this criterion. If largefiles is specified, there is no such guarantee. The default behavior is largefiles. If nolargefiles is specified, mount will fail for ufs if the file system to be mounted has contained a large file (a file whose size is greater than or equal to 2 Gbyte) since the last invocation of fsck on the file system. The large file need not be present in the file system at the time of the mount for the mount to fail; it could have been created previously and destroyed. Invoking fsck (see fsck_ufs(1M)) on the file system will reset the file system state if no large files are present. After invoking fsck, a successful mount of the file system with nolargefiles specified indicates the absence of large files in the file system; an unsuc- cessful mount attempt indicates the presence of at least one large file. logging | nologging If logging is specified, then logging is enabled for the duration of the mounted file system. Logging is the process of storing transactions (changes that make up a complete UFS operation) in a log before the transactions are applied to the file system. Once a transaction is stored, the transaction can be applied to the file system later. This prevents file systems from becoming incon- sistent, therefore reducing the possibility that fsck might run. And, if fsck is bypassed, logging generally reduces the time required to reboot a system. The default behavior is logging for all UFS file systems. The log is allocated from free blocks in the file system, and is sized approximately 1 Mbyte per 1 Gbyte of file system, up to a maximum of 64 Mbytes. Logging is enabled on any UFS file system, including root (/), except under the following conditions: o When logging is specifically disabled. o If there is insufficient file system space for the log. In this case, the following message is displayed and file system is still mounted: # mount /dev/dsk/c0t4d0s0 /mnt /mnt: No space left on device Could not enable logging for /mnt on /dev/dsk/c0t4d0s0. The log created by UFS logging is continually flushed as it fills up. The log is totally flushed when the file system is unmounted or as a result of the lockfs -f command. m Mount the file system without making an entry in /etc/mnttab. noatime By default, the file system is mounted with normal access time (atime) recording. If noatime is specified, the file system will ignore access time updates on files, except when they coincide with updates to the ctime or mtime. See stat(2). This option reduces disk activity on file systems where access times are unimportant (for example, a Usenet news spool). noatime turns off access time recording regardless of dfratime or nodfratime. The POSIX standard requires that access times be marked on files. -noatime ignores them unless the file is also modified. onerror = action This option specifies the action that UFS should take to recover from an internal inconsistency on a file system. Specify action as panic, lock, or umount. These values cause a forced system shutdown, a file system lock to be applied to the file system, or the file system to be forcibly unmounted, respectively. The default is panic. quota Quotas are turned on for the file system. remount Remounts a file system with a new set of options. All options not explicitly set with remount revert to their default values. rq Read-write with quotas turned on. Equivalent to rw, quota. -O Overlay mount. Allow the file system to be mounted over an existing mount point, making the underlying file system inaccessible. If a mount is attempted on a pre-existing mount point without setting this flag, the mount will fail, producing the error "device busy". The mount_ufs command supports the xattr flag, to allow the creation and manipulation of extended attributes. See fsattr(5) for a descrip- tion of extended attributes. The xattr flag is always on. EXAMPLES
Example 1: Turning Off (and On) Logging The following command turns off logging on an already mounted file system. The subsequent command restores logging. # mount -F ufs -o remount,nologging /export # (absence of message indicates success) # mount -F ufs -o remount,logging /export In the preceding commands, the -F ufs option is not necessary. FILES
/etc/mnttab table of mounted file systems /etc/vfstab list of default parameters for each file system ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ SEE ALSO
fsck(1M), fsck_ufs(1M), mount(1M), mountall(1M), fcntl(2), mount(2), stat(2), mnttab(4), vfstab(4), attributes(5), fsattr(5), largefile(5) NOTES
Since the root (/) file system is mounted read-only by the kernel during the boot process, only the remount option (and options that can be used in conjunction with remount) affect the root (/) entry in the /etc/vfstab file. SunOS 5.10 27 Aug 2004 mount_ufs(1M)

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