Red Hat ENTERPRISE LINUX 5 - DEPLOYMENT Deployment Manual page 68

Chapter 3. The proc File System
Can write CD-RW:
Can read DVD:
Can write DVD-R:
Can write DVD-RAM:
Can read MRW:
Can write MRW:
Can write RAM:
This file can be quickly scanned to discover the qualities of an unknown CD-ROM. If multiple CD-
ROMs are available on a system, each device is given its own column of information.
Various files in /proc/sys/dev/cdrom, such as autoclose and checkmedia, can be used to
control the system's CD-ROM. Use the echo command to enable or disable these features.
If RAID support is compiled into the kernel, a /proc/sys/dev/raid/ directory becomes available
with at least two files in it: speed_limit_min and speed_limit_max. These settings determine the
acceleration of RAID devices for I/O intensive tasks, such as resyncing the disks.
3.3.9.2. /proc/sys/fs/
This directory contains an array of options and information concerning various aspects of the file
system, including quota, file handle, inode, and dentry information.
The binfmt_misc/ directory is used to provide kernel support for miscellaneous binary formats.
The important files in /proc/sys/fs/ include:
• dentry-state — Provides the status of the directory cache. The file looks similar to the following:
57411 52939 45 0 0 0
The first number reveals the total number of directory cache entries, while the second number
displays the number of unused entries. The third number tells the number of seconds between
when a directory has been freed and when it can be reclaimed, and the fourth measures the pages
currently requested by the system. The last two numbers are not used and display only zeros.
• dquot-nr — Lists the maximum number of cached disk quota entries.
• file-max — Lists the maximum number of file handles that the kernel allocates. Raising the value
in this file can resolve errors caused by a lack of available file handles.
• file-nr — Lists the number of allocated file handles, used file handles, and the maximum number
of file handles.
• overflowgid and overflowuid — Defines the fixed group ID and user ID, respectively, for use
with file systems that only support 16-bit group and user IDs.
• super-max — Controls the maximum number of superblocks available.
• super-nr — Displays the current number of superblocks in use.
3.3.9.3. /proc/sys/kernel/
This directory contains a variety of different configuration files that directly affect the operation of the
kernel. Some of the most important files include:
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