Pantek Library
Hosting Provided By
CybrHost
High Speed Hosting
Operating Systems: Redhat > The Official Red Hat Linux 9 Reference Guides1-proc-directories.html (Request Expert Redhat Support)
Red Hat Linux 9: Red Hat Linux Reference Guide
PrevChapter 5. The proc File SystemNext

5.3. Directories in /proc/

Common groups of information concerning the kernel are grouped into directories and subdirectories within the /proc/ directory.

5.3.1. Process Directories

Every /proc/ directory contains a number of directories with numerical names. A listing of them may begins like this: 
dr-xr-xr-x    3 root     root            0 Feb 13 01:28 1
dr-xr-xr-x    3 root     root            0 Feb 13 01:28 1010
dr-xr-xr-x    3 xfs      xfs             0 Feb 13 01:28 1087
dr-xr-xr-x    3 daemon   daemon          0 Feb 13 01:28 1123
dr-xr-xr-x    3 root     root            0 Feb 13 01:28 11307
dr-xr-xr-x    3 apache   apache          0 Feb 13 01:28 13660
dr-xr-xr-x    3 rpc      rpc             0 Feb 13 01:28 637
dr-xr-xr-x    3 rpcuser  rpcuser         0 Feb 13 01:28 666

These directories are called process directories, as they are named after a program's process ID and contain information specific to that process. The owner and group of each process directory is set to the user running the process. When the process is terminated, its /proc/ process directory vanishes.

Each process directory contains the following files:

5.3.1.1. /proc/self/

The /proc/self/ directory is a link to the currently running process. This allows a process to look at itself without having to know its process ID.

Within a shell environment, a listing of the /proc/self/ directory produces the same contents as listing the process directory for that process.

5.3.2. /proc/bus/

This directory contains information specific to the various buses available on the system. So, for example, on a standard system containing ISA, PCI, and USB busses, current data on each of these buses is available in its directory under /proc/bus/.

The contents of the subdirectories and files available varies greatly on the precise configuration of the system. However, each of the directories for each of the bus types has at least one directory for each bus of that type. These individual bus directories, usually signified with numbers, such as 00, contain binary files that refer to the various devices available on that bus.

So, for example, a system with a USB bus but no USB devices connected to it has a /proc/bus/usb/ directory containing several files: 

total 0
dr-xr-xr-x    1 root     root            0 May  3 16:25 001
-r--r--r--    1 root     root            0 May  3 16:25 devices
-r--r--r--    1 root     root            0 May  3 16:25 drivers

The /proc/bus/usb/ directory contains files that track the various devices on any USB buses, as well as the drivers required to use them. The /proc/bus/usb/001/ directory contains all devices on the first USB bus. By looking at the contents of the devices file, one can identify the USB root hub on the motherboard: 
T:  Bus=01 Lev=00 Prnt=00 Port=00 Cnt=00 Dev#=  1 Spd=12  MxCh= 2
B:  Alloc=  0/900 us ( 0%), #Int=  0, #Iso=  0
D:  Ver= 1.00 Cls=09(hub  ) Sub=00 Prot=00 MxPS= 8 #Cfgs=  1
P:  Vendor=0000 ProdID=0000 Rev= 0.00
S:  Product=USB UHCI Root Hub
S:  SerialNumber=d400
C:* #Ifs= 1 Cfg#= 1 Atr=40 MxPwr=  0mA
I:  If#= 0 Alt= 0 #EPs= 1 Cls=09(hub  ) Sub=00 Prot=00 Driver=hub
E:  Ad=81(I) Atr=03(Int.) MxPS=   8 Ivl=255ms

5.3.3. /proc/driver/

This directory contains information for specific drivers in use by the kernel.

A common file found here is rtc, which provides output from the driver for the system's Real Time Clock (RTC), the device that keeps the time while the system is switched off. Sample output from /proc/driver/rtc looks like this: 
rtc_time	: 01:38:43
rtc_date	: 1998-02-13
rtc_epoch	: 1900
alarm		: 00:00:00
DST_enable	: no
BCD		: yes
24hr		: yes
square_wave	: no
alarm_IRQ	: no
update_IRQ	: no
periodic_IRQ	: no
periodic_freq	: 1024
batt_status	: okay

For more information about the RTC, review /usr/src/linux-2.4/Documentation/rtc.txt.

5.3.4. /proc/fs

This directory shows which file systems are exported. If running an NFS server, typing cat /proc/fs/nfs/exports will display the file systems being shared and the permissions granted for those file systems. For more on sharing file system with NFS, see Chapter 9 Network File System (NFS).

5.3.5. /proc/ide/

This directory holds information about IDE devices on the system. Each IDE channel is represented as a separate directory, such as /proc/ide/ide0 and /proc/ide/ide1. In addition, a drivers file is also available, providing the version number of the various drivers used on the IDE channels: 
ide-cdrom version 4.59
ide-floppy version 0.97
ide-disk version 1.10

Many chipsets also provide an informational file in this directory that gives additional data concerning the drives connected through the channels. For example, a generic Intel PIIX4 Ultra 33 chipset produces a /proc/ide/piix that will tell you whether DMA or UDMA is enabled for the devices on the IDE channels: 


                              Intel PIIX4 Ultra 33 Chipset.
------------- Primary Channel ---------------- Secondary Channel -------------
                 enabled                          enabled
------------- drive0 --------- drive1 -------- drive0 ---------- drive1 ------
DMA enabled:    yes              no              yes               no 
UDMA enabled:   yes              no              no                no 
UDMA enabled:   2                X               X                 X
UDMA
DMA
PIO

Navigating into the directory for an IDE channel, such as ide0, provides additional information. The channel file provides the channel number, while the model tells you the bus type for the channel (such as pci).

5.3.5.1. The Device Directory

Within each IDE channel directory is a device directory. The name of the device directory corresponds to the drive letter in the /dev/ directory. For instance, the first IDE drive on ide0 would be hda.

NoteNote
 

There is a symbolic link to each of these device directories in the /proc/ide/ directory.

Each device directory contains a collection of information and statistics. The contents of these directories vary according to the type of device connected. Some of the more useful files common to many devices include:

5.3.6. /proc/irq/

This directory is used to set IRQ to CPU affinity, which allows the system to connect a particular IRQ to only one CPU. Alternatively, it can exclude a CPU from handling any IRQs.

Each IRQ has its own directory, allowing for the individual configuration of each IRQ. The /proc/irq/prof_cpu_mask file is a bitmask that contains the default values for the smp_affinity file in the IRQ directory. The values in smp_affinity specify which CPUs handle that particular IRQ.

For more information about the /proc/irq/ directory, consult: 
/usr/src/linux-2.4/Documentation/filesystems/proc.txt

5.3.7. /proc/net/

This directory provides a comprehensive look at various networking parameters and statistics. Each of the files covers a specific range of information related to networking on the system. Below is a partial listing of these virtual files:

Call Pantek today for Open Source Technical Support at 1-877-546-8934 - 24/7/365X

5.3.8. /proc/scsi/

This directory is analogous to the /proc/ide/ directory, however, it is only for connected SCSI devices.

The primary file in this directory is /proc/scsi/scsi, which contains a list of every recognized SCSI device. From this listing, the type of device, as well as the model name, vendor, SCSI channel and ID data is available.

For example, if a system contains a SCSI CD-ROM, a tape drive, a hard drive, and a RAID controller, this file would look similar to this: 
Attached devices: 
Host: scsi1 Channel: 00 Id: 05 Lun: 00
  Vendor: NEC      Model: CD-ROM DRIVE:466 Rev: 1.06
  Type:   CD-ROM                           ANSI SCSI revision: 02
Host: scsi1 Channel: 00 Id: 06 Lun: 00
  Vendor: ARCHIVE  Model: Python 04106-XXX Rev: 7350
  Type:   Sequential-Access                ANSI SCSI revision: 02
Host: scsi2 Channel: 00 Id: 06 Lun: 00
  Vendor: DELL     Model: 1x6 U2W SCSI BP  Rev: 5.35
  Type:   Processor                        ANSI SCSI revision: 02
Host: scsi2 Channel: 02 Id: 00 Lun: 00
  Vendor: MegaRAID Model: LD0 RAID5 34556R Rev: 1.01
  Type:   Direct-Access                    ANSI SCSI revision: 02

Each SCSI driver used by the system has its own directory in /proc/scsi/, which contains files specific to each SCSI controller using that driver. So, for the example system just addressed, aic7xxx and megaraid directories are present, as those two drivers are being utilized. The files in each of the directories typically contain an I/O address range, IRQ information, and statistics for the particular SCSI controller using that driver. Each controller can report a different type and amount of information. The Adaptec AIC-7880 Ultra SCSI host adapter's file in this example system produces the following output: 
Adaptec AIC7xxx driver version: 5.1.20/3.2.4
Compile Options:
  TCQ Enabled By Default : Disabled
  AIC7XXX_PROC_STATS     : Enabled
  AIC7XXX_RESET_DELAY    : 5

Adapter Configuration:
           SCSI Adapter: Adaptec AIC-7880 Ultra SCSI host adapter
                           Ultra Narrow Controller
    PCI MMAPed I/O Base: 0xfcffe000
 Adapter SEEPROM Config: SEEPROM found and used.
      Adaptec SCSI BIOS: Enabled
                    IRQ: 30
                   SCBs: Active 0, Max Active 1,
                         Allocated 15, HW 16, Page 255
             Interrupts: 33726
      BIOS Control Word: 0x18a6
   Adapter Control Word: 0x1c5f
   Extended Translation: Enabled
Disconnect Enable Flags: 0x00ff
     Ultra Enable Flags: 0x0020
 Tag Queue Enable Flags: 0x0000
Ordered Queue Tag Flags: 0x0000
Default Tag Queue Depth: 8
    Tagged Queue By Device array for aic7xxx host instance 1:
      {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
    Actual queue depth per device for aic7xxx host instance 1:
      {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}

Statistics:


(scsi1:0:5:0)
  Device using Narrow/Sync transfers at 20.0 MByte/sec, offset 15
  Transinfo settings: current(12/15/0/0), goal(12/15/0/0), user(12/15/0/0)
  Total transfers 0 (0 reads and 0 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+   128K+
   Reads:       0       0       0       0       0       0       0       0
  Writes:       0       0       0       0       0       0       0       0


(scsi1:0:6:0)
  Device using Narrow/Sync transfers at 10.0 MByte/sec, offset 15
  Transinfo settings: current(25/15/0/0), goal(12/15/0/0), user(12/15/0/0)
  Total transfers 132 (0 reads and 132 writes)
             < 2K      2K+     4K+     8K+    16K+    32K+    64K+   128K+
   Reads:       0       0       0       0       0       0       0       0
  Writes:       0       0       0       1     131       0       0       0

This output reveals the transfer speed to the various SCSI devices connected to the controller based on channel ID, as well as detailed statistics concerning the amount and sizes of files read or written by that device. For example, this controller is communicating with the CD-ROM at 20 megabytes per second, while the tape drive is only communicating at 10 megabytes per second.

5.3.9. /proc/sys/

The /proc/sys/ directory is different from others in /proc/ because it not only provides information about the system but also allows the system administrator to immediately enable and disable kernel features.

WarningWarning
 

Use caution when changing settings on a production system using the various files in the /proc/sys/ directory. Changing the wrong setting may render the kernel unstable, requiring a system reboot.

For this reason, be sure the options are valid for that file before attempting to change any value in /proc/sys/.

A good way to determine if a particular file can be configured, or if it is only designed to provide information, is to list it with the -l option at the shell prompt. If the file is writable, it may be used to configure the kernel. For example, a partial listing of /proc/sys/fs looks like this: 
-r--r--r--    1 root     root            0 May 10 16:14 dentry-state
-rw-r--r--    1 root     root            0 May 10 16:14 dir-notify-enable
-r--r--r--    1 root     root            0 May 10 16:14 dquot-nr
-rw-r--r--    1 root     root            0 May 10 16:14 file-max
-r--r--r--    1 root     root            0 May 10 16:14 file-nr

In this listing, the files dir-notify-enable and file-max can be written to and, therefore, can be used to configure the kernel. The other files only provide feedback on current settings.

Changing a value within a /proc/sys/ file is done by echoing the new value into the file. For example, to enable the System Request Key on a running kernel, type the command: 
echo 1 > /proc/sys/kernel/sysrq

This will change the value for sysrq from 0 (off) to 1 (on).

The purpose of the System Request Key is to allow immediate input to the kernel through simple key combinations. For example, the System Request Key can be used to immediately shut down or restart a system, sync all mounted file systems, or dump important information to your console. This feature is most useful when using a development kernel or when experiencing system freezes. However, it is considered a security risk for an unattended console and is therefore turned off by default under Red Hat Linux.

Refer to /usr/src/linux-2.4/Documentation/sysrq.txt for more information on the System Request Key.

A few /proc/sys/ configuration files contain more than one value. In order to correctly send new values to them, place a space character between each value passed with the echo command, such as is done in this example: 
echo 4 2 45 > /proc/sys/kernel/acct

NoteNote
 

Any configuration changes made using the echo command will disappear when the system is restarted. To make configuration changes take effect after the system is rebooted, see Section 5.4 Using the sysctl Command.

The /proc/sys/ directory contains several subdirectories controlling different aspects of a running kernel.

5.3.9.1. /proc/sys/dev/

This directory provides parameters for particular devices on the system. Most systems have at least two directories, cdrom and raid. Customized kernels can have other directories, such as parport, which provides the ability to share one parallel port between multiple device drivers.

The cdrom directory contains a file called info, which reveals a number of important CD-ROM parameters: 
CD-ROM information, Id: cdrom.c 3.12 2000/10/18

drive name:		hdc
drive speed:		32
drive # of slots:	1
Can close tray:		1
Can open tray:		1
Can lock tray:		1
Can change speed:	1
Can select disk:	0
Can read multisession:	1
Can read MCN:		1
Reports media changed:	1
Can play audio:		1
Can write CD-R:		0
Can write CD-RW:	0
Can read DVD:		0
Can write DVD-R:	0
Can write DVD-RAM:	0

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 will be 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.

5.3.9.2. /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:

5.3.9.3. /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: