Red Hat LINUX 7.2 Reference Manual

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[Page 1] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Red Hat Linux 7.2 The Official Red Hat Linux Reference Guide ...

[Page 2] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

ISBN: N/A Red Hat, Inc. 2600 Meridian Parkway Durham, NC 27713 USA +1 919 547 0012 (Voice) +1 919 547 0024 (FAX) 888 733 4281 (Voice) P.O. Box 13588 Research Triangle Park, NC 27709 USA © 2001 Red Hat, Inc. rhl-rg(EN)-7.2-Print-RHI (2001-08-30T12:53...

[Page 3] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Contents Red Hat Linux 7.2 Introduction................................................................................... ix Finding Appropriate Documentation ..................................................... ix Document Conventions................

[Page 4] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

3.7 Differences in the Boot Process of Other Architectures ...................... 57 Chapter 4 The /proc Filesystem.............................................. 59 4.1 A Virtual Filesystem ...............................................................

[Page 5] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Chapter 8 Using Kerberos 5 on Red Hat Linux .................... 139 8.1 Why Use Kerberos? .............................................................. 139 8.2 Why Not Use Kerberos? ......................................................... 139 8.3 ...

[Page 6] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

11.12 Tripwire and Email................................................................ 179 11.13 Additional Resources ............................................................ 180 Part III Network Services Reference.................................

[Page 7] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

15.7 OpenLDAP Daemons and Utilities.............................................. 252 15.8 Modules for Adding Extra Functionality to LDAP.............................. 253 15.9 LDAP How To: A Quick Overview...............................................

[Page 8] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

A.2 CD-ROM Module Parameters ................................................... 312 A.3 SCSI parameters ................................................................. 315 A.4 Ethernet parameters ......................................................

[Page 9] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 0.1:Finding Appropriate Documentation ix Introduction Welcome to the Official Red Hat Linux Reference Guide. The Official Red Hat Linux Reference Guide contains useful information about your Red Hat Linux system. From fundamental concepts, su...

[Page 10] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

x Introduction This type of user has never used any Linux (or Linux-like) operating system before or has had only limited exposure to Linux. They may or may not have experience using other operating systems (such as Windows). Is this you? If so, skip...

[Page 11] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 0.1:Finding Appropriate Documentation xi approach to doing things, you may find yourself intimidated by the sheer number of commands available on your Red Hat Linux system. Keep in mind that you do not have to memorize all of the available Li...

[Page 12] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

xii Introduction • linux.redhat.rpm — A good place to go if you are having trouble using RPM to accomplish particular objectives. Beginning Linux Books • Red Hat Linux for Dummies, 2nd Edition by Jon "maddog" Hall; IDG • Special Edi...

[Page 13] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 0.2:Document Conventions xiii Document Conventions When you read this manual, you will see that certain words are represented in different fonts, type- faces, sizes and weights. This highlighting is systematic; different words are represented...

[Page 14] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

xiv Introduction The [Ctrl]-[Alt]-[Backspace] key combination will restart the X Window System. text found on a GUI interface A title, word or phrase found on a GUI interface screen or window will be shown in this style. When you see text shown in th...

[Page 15] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 0.2:Document Conventions xv A prompt, which is a computer’s way of signifying that it is ready for you to input something, will be shown in this style. Examples: $ # [stephen@maturin stephen]$ leopard login: user input Text that the user ha...

[Page 16] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

xvi Introduction CAUTION Do not do routine tasks as root — use a regular user account unless you need to use the root account to administer your system. WARNING If you choose not to partition manually, a server installation will remove all existing...

[Page 17] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 0.6:Sign Up for Support xvii to system structure and organization, new and powerful security tools, and other resources to help you extend the power of your Red Hat Linux system — and your ability to use it. That’s where you can help. We ...

[Page 18] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

xviii Introduction The Red Hat Documentation Team ...

[Page 19] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Part I System Reference ...

[Page 20] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

...

[Page 21] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 1.2:Overview of Filesystem Hierarchy Standard (FHS) 21 1 Filesystem Structure 1.1 Why Share a Common Structure? An operating system’s filesystem structure is its most basic level of organization. Almost all of the ways an operating system i...

[Page 22] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

22 Chapter 1:Filesystem Structure The current FHS document is the authoritative reference to any FHS-compliant filesystem, but the standard leaves many areas undefined or extensible. In this section, we provide an overview of the standard and a descr...

[Page 23] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 1.2:Overview of Filesystem Hierarchy Standard (FHS) 23 The /opt Directory The /opt directory provides an area for usually large, static application software packages to be stored. For packages that wish to avoid putting their files throughout...

[Page 24] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

24 Chapter 1:Filesystem Structure reboot, route, shutdown, swapoff, swapon, update The /usr Directory The /usr directory is for files that can be shared across a whole site. The /usr directory usually has its own partition, and it should be mountable...

[Page 25] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 1.2:Overview of Filesystem Hierarchy Standard (FHS) 25 |- bin |- doc |- etc |- games |- include |- lib |- libexec |- sbin |- share |- src The /var Directory Since the FHS requires that you be able to mount /usr read-only, any programs that wr...

[Page 26] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

26 Chapter 1:Filesystem Structure |- news |- rwho |- samba |- slrnpull |- squid |- up2date |- uucp |- uucppublic |- vbox |- voice |- tmp |- www |- yp System log files such as messages and lastlog go in /var/log. The /var/lib/rpm direc- tory also cont...

[Page 27] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 2.2:Standard Users 27 2 Users and Groups The control of users and groups exists at the core of Red Hat Linux system administration. Users can be either people (accounts tied to a physical user) or logical users (accounts that exist for applic...

[Page 28] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

28 Chapter 2:Users and Groups User UID GID Home Directory Shell lp 4 7 /var/spool/lpd sync 5 0 /sbin /bin/sync shutdown 6 0 /sbin /sbin/shutdown halt 7 0 /sbin /sbin/halt mail 8 12 /var/spool/mail news 9 13 /var/spool/news uucp 10 14 /var/spool/uucp ...

[Page 29] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 2.3:Standard Groups 29 User UID GID Home Directory Shell rpcuser 29 29 /var/lib/nfs junkbust 73 73 /etc/junkbuster gdm 42 42 /var/gdm squid 23 23 /var/spool/squid /dev/null nscd 28 28 / rpm 37 37 /var/lib/rpm mailman 41 41 /var/mailman radvd ...

[Page 30] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

30 Chapter 2:Users and Groups Group GID Members wheel 10 root mail 12 mail news 13 news uucp 14 uucp man 15 games 20 gopher 30 dip 40 ftp 50 nobody 99 users 100 piranha 60 piranha ident 98 ident rpc 32 rpc pvm 24 pvm floppy 19 utmp 22 slocate 21 pppu...

[Page 31] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 2.4:User Private Groups 31 Group GID Members mailnull 47 mailnull rpcusers 29 xfs 43 xfs gdm 42 gdm apache 48 apache squid 23 squid named 25 named junkbust 73 junkbust mysql 27 mysql mailman 41 mailman ldap 55 ldap 2.4 User Private Groups Red...

[Page 32] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

32 Chapter 2:Users and Groups difficult because when someone creates a file, it is associated with the primary group to which they belong. When a single person works on multiple projects, it is difficult to associate the right files with the right gr...

[Page 33] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 2.5:Shadow Utilities 33 to associate the contents of the directory with the emacs group and add the proper users to the group: /usr/bin/gpasswd -a < username > emacs • To allow the users to actually create files in the directory you e...

[Page 34] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

34 Chapter 2:Users and Groups The shadow-utils package contains a number of utilities that support: • Conversion from normal to shadow passwords and back (pwconv, pwunconv) • Verification of the password, group, and associated shadow files (pwck,...

[Page 35] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.2:Behind the Scenes of the Boot Process 35 3 Boot Process, Init, and Shutdown This chapter contains information on what happens when you boot or shut down your Red Hat Linux system. Note This chapter focuses on LILO, the default boot loader...

[Page 36] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

36 Chapter 3:Boot Process, Init, and Shutdown and is always available for use. The BIOS provides the lowest level interface to peripheral devices and controls the first step of the boot process. The BIOS tests the system, looks for and checks periphe...

[Page 37] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.2:Behind the Scenes of the Boot Process 37 boot=/dev/hda map=/boot/map install=/boot/boot.b prompt timeout=50 message=/boot/message lba32 default=linux image=/boot/vmlinuz-2.4.0-0.43.6 label=linux initrd=/boot/initrd-2.4.0-0.43.6.img read-o...

[Page 38] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

38 Chapter 3:Boot Process, Init, and Shutdown • image=/boot/vmlinuz-2.4.0-0.43.6 specifies the linux kernel to boot with this par- ticular boot option. • label=linux names the operating system option in the LILO screen. In this case, it also is t...

[Page 39] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.2:Behind the Scenes of the Boot Process 39 When init starts, it becomes the parent or grandparent of all of the processes that start up automati- cally on your Red Hat Linux system. First, it runs the /etc/rc.d/rc.sysinit script, which sets...

[Page 40] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

40 Chapter 3:Boot Process, Init, and Shutdown in a particular order so that they start in that order. You can change the order in which the services start up or are killed by changing the name of the symbolic link that refers to the script that actua...

[Page 41] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.2:Behind the Scenes of the Boot Process 41 S06reconfig -> ../init.d/reconfig S08ipchains -> ../init.d/ipchains S10network -> ../init.d/network S12syslog -> ../init.d/syslog S13portmap -> ../init.d/portmap S14nfslock -> ../...

[Page 42] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

42 Chapter 3:Boot Process, Init, and Shutdown initiates a login process for that user. This allows users to authenticate themselves to the system and begin to use it. Also, /etc/inittab tells init how it should handle a user hitting [Ctrl]-[Alt]-[Del...

[Page 43] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.3:Sysconfig Information 43 • rc.sysinit handles most of the boot loader’s processes and then runs rc.serial (if it ex- ists) • init runs all the scripts for the default runlevel • init runs /etc/rc.d/rc.local The default runlevel is...

[Page 44] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

44 Chapter 3:Boot Process, Init, and Shutdown • authconfig • cipe • clock • desktop • firewall • harddisks • hwconf • i18n • init • ipchains • iptables • irda • keyboard • kudzu • mouse • network • pcmcia • rawdevi...

[Page 45] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.3:Sysconfig Information 45 /etc/sysconfig/apmd The /etc/sysconfig/apmd file is used by apmd as a configuration for what things to start/stop/change on suspend or resume. It is set up to turn on or off apmd during startup, depending on wheth...

[Page 46] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

46 Chapter 3:Boot Process, Init, and Shutdown • UTC= <value> , where <value> is one of the following boolean values: – true — Indicates that the clock is set to Universal Time. Any other value indicates that it is set to local time....

[Page 47] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.3:Sysconfig Information 47 • Multiple_IO=16, where a setting of 16 allows for multiple sectors per I/O interrupt. When enabled, this feature reduces operating system overhead by 30-50%. Use with caution. • EIDE_32BIT=3 enables (E)IDE 32...

[Page 48] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

48 Chapter 3:Boot Process, Init, and Shutdown • SETCOLOR_FAILURE= <value> , where <value> sets the color to a color indicating failure. Defaults to ANSI sequences output by echo -e, setting the color to red. • SETCOLOR_WARNING= <va...

[Page 49] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.3:Sysconfig Information 49 The following values may be used: • IRDA= <value> , where <value> is one of the following boolean values: – yes — irattach will be run, which periodically checks to see if anything is trying to c...

[Page 50] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

50 Chapter 3:Boot Process, Init, and Shutdown • SAFE= <value> , where <value> is one of the following: – yes — kuzdu does a safe probe. – no — kuzdu does a normal probe. /etc/sysconfig/mouse The /etc/sysconfig/mouse file is used...

[Page 51] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.3:Sysconfig Information 51 /etc/sysconfig/network The /etc/sysconfig/network file is used to specify information about the desired network configuration. The following values may be used: • NETWORKING= <value> , where <value> ...

[Page 52] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

52 Chapter 3:Boot Process, Init, and Shutdown • PCIC_OPTS= <value> , where <value> is the socket driver (i82365 or tcic) timing parame- ters. • CORE_OPTS= <value> , where <value> is the list of pcmcia_core options. • CAR...

[Page 53] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.3:Sysconfig Information 53 /etc/sysconfig/ups The /etc/sysconfig/ups file is used to specify information about any Uninterruptible Power Supplies (UPS) connected to your system. A UPS can be very valuable for a Red Hat Linux system because ...

[Page 54] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

54 Chapter 3:Boot Process, Init, and Shutdown • VNCSERVERS= <value> , where <value> is set to something like "1:fred", to indicate that a VNC server should be started for user fred on display :1. User fred must have set a VNC ...

[Page 55] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.4:Init Runlevels 55 them to quickly move in and out of their custom configuration without disturbing the normal set of features at the standard runlevels. If your machine gets into a state where it will not boot due to a bad /etc/inittab or...

[Page 56] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

56 Chapter 3:Boot Process, Init, and Shutdown 3.5 Running Programs at Boot Time The file /etc/rc.d/rc.local script is run by init at boot time, after all other initialization is complete, and whenever you change runlevels. You can add additional init...

[Page 57] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 3.7:Differences in the Boot Process of Other Architectures 57 3.7 Differences in the Boot Process of Other Architectures Each computer architecture supported by Red Hat Linux boots the operating system in a different way. However, once the Re...

[Page 58] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

58 Chapter 3:Boot Process, Init, and Shutdown ...

[Page 59] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.1:A Virtual Filesystem 59 4 The /proc Filesystem The /proc directory contains virtual files that are windows into the current state of the running Linux kernel. This allows the user to peer into a vast array of information, effectively prov...

[Page 60] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

60 Chapter 4:The /proc Filesystem -r--r--r-- 1 root root 0 May 3 11:42 execdomains -r--r--r-- 1 root root 0 May 3 11:42 fb -r--r--r-- 1 root root 0 May 3 11:42 filesystems [root@bleach /]# The /proc virtual files exhibit some interesting qualities. F...

[Page 61] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.1:A Virtual Filesystem 61 [root@bleach /]# cat /proc/cpuinfo processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 6 model name : Celeron (Mendocino) stepping : 0 cpu MHz : 416.537 cache size : 128 KB fdiv_bug : no hlt_bug : no f00f...

[Page 62] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

62 Chapter 4:The /proc Filesystem 4.2 Top-Level Files in /proc Most of the files at the top-level of the /proc directory hold key pieces of information about the state of the Linux kernel and your system in general. It is important to remember that t...

[Page 63] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 63 When the same machine is unplugged from its power source and running on its own batteries for a few minutes, you will see the contents of the apm file change: 1.14 1.2 0x03 0x00 0x00 0x01 99% 1792 min In this s...

[Page 64] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

64 Chapter 4:The /proc Filesystem fpu : yes fpu_exception : yes cpuid level : 2 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 sep mtrr pge mca cmov bogomips : 666.82 Quite a bit of information is available here. Among the highlights: • proces...

[Page 65] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 65 162 raw 180 usb Block devices: 1 ramdisk 2fd 3 ide0 9md 22 ide1 The output from /proc/devices includes the major number and name of the device. Character devices are similar to block devices, except for two bas...

[Page 66] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

66 Chapter 4:The /proc Filesystem 0-255 Linux [kernel] Think of execution domains as a kind of "personality" of a particular operating system. Other bi- nary formats, such as Solaris, UnixWare, and FreeBSD, can be used with Linux. By changi...

[Page 67] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 67 1: 339 XT-PIC keyboard 2: 0 XT-PIC cascade 5: 80111 XT-PIC usb-uhci, eth0 8: 1 XT-PIC rtc 12: 6107 XT-PIC PS/2 Mouse 14: 60324 XT-PIC ide0 15: 541741 XT-PIC ide1 NMI: 0 ERR: 0 For a multi-processor machine, thi...

[Page 68] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

68 Chapter 4:The /proc Filesystem 00000000-0009fbff : System RAM 0009fc00-0009ffff : reserved 000a0000-000bffff : Video RAM area 000c0000-000c7fff : Video ROM 000f0000-000fffff : System ROM 00100000-03ffcfff : System RAM 00100000-002557df : Kernel co...

[Page 69] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 69 4.2.12 /proc/isapnp This file lists Plug and Play (PnP) cards in ISA slots on the system. This is most often seen with sound cards but may include any number of devices. A /proc/isapnp file with Soundblaster en...

[Page 70] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

70 Chapter 4:The /proc Filesystem Do not try to cat or otherwise attempt to view this file. Its contents are designed to be examined by a debugger, such as gdb, the GNU Debugger. Only the root user has the rights to view this file. 4.2.14 /proc/kmsg ...

[Page 71] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 71 Each lock is assigned a unique number at the beginning of each line. The second column refers to the class of lock used, with FLOCK signifying the older-style UNIX file locks from a flock system call and POSIX ...

[Page 72] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

72 Chapter 4:The /proc Filesystem MemFree: 8108 kB MemShared: 0 kB Buffers: 117916 kB Cached: 47548 kB Active: 135300 kB Inact_dirty: 29276 kB Inact_clean: 888 kB Inact_target: 0 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 255576 kB LowFree: 8108 kB ...

[Page 73] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 73 • LowTotal and LowFree — The total and free amount of memory, respectively, that is directly mapped into kernel space. The LowTotal value can vary based on the type of kernel used. • SwapTotal — The tot...

[Page 74] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

74 Chapter 4:The /proc Filesystem none /dev/pts devpts rw 0 0 automount(pid696) /misc autofs rw 0 0 The output found here is similar to contents of /etc/mtab, except that /proc/mount can be more current. The first column specifies the device that is ...

[Page 75] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 75 • name — The name of the partition. 4.2.25 /proc/pci This file contains a full listing of every PCI device on your system. Depending on the number of PCI devices you have, /proc/pci can get rather long. An ...

[Page 76] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

76 Chapter 4:The /proc Filesystem 4.2.26 /proc/slabinfo This file gives information about memory usage on the slab level. Linux kernels greater than 2.2 use slab pools to manage memory above the page level. Commonly used objects have their own slab p...

[Page 77] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.2:Top-Level Files in /proc 77 kstat.inputqueue_no_packet: 0 Some of the more popular statistics include: • cpu — Measures the number of jiffies (1/100ths of a second) that the system has been in user mode, user mode with low priority (n...

[Page 78] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

78 Chapter 4:The /proc Filesystem This information is used for a variety of purposes, including providing the version data at the standard login prompt. 4.3 Directories in /proc Common groups of information concerning the kernel is grouped into direc...

[Page 79] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 79 • environ — Gives a list of the environment variables for the process. The environment variable is given in all upper-case characters, and the value is in lower-case characters. • exe — A link to the execut...

[Page 80] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

80 Chapter 4:The /proc Filesystem 3. Number of pages that are shared 4. Number of pages are code 5. Number of pages of data/stack 6. Number of pages of library 7. Number of dirty pages • status — Provides the status of the process in a form that ...

[Page 81] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 81 4.3.2 /proc/bus This directory contains information specific to the various busses available on the system. So, for example, on a standard system containing ISA, PCI, and USB busses, current data on each of these b...

[Page 82] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

82 Chapter 4:The /proc Filesystem 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 lo...

[Page 83] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 83 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 for the first channel, provides addi- tional information. The ...

[Page 84] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

84 Chapter 4:The /proc Filesystem max_kb_per_request 64 1 127 rw multcount 8 0 8 rw nice1 1 0 1 rw nowerr 0 0 1 rw number 0 0 3 rw pio_mode write-only 0 255 w slow 0 0 1 rw unmaskirq 0 0 1 rw using_dma 1 0 1 rw 4.3.6 /proc/irq This directory is used ...

[Page 85] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 85 input ACCEPT 1 0 93537 0 12626171 forward ACCEPT 1 0 0 0 0 output ACCEPT 1 0 14270 0 3796697 • ip_masquerade — Provides a table of masquerading information. • ip_mr_cache — List of the multicast routing cac...

[Page 86] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

86 Chapter 4:The /proc Filesystem 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-XX...

[Page 87] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 87 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: {255,255,255,255,255,255,255,255,255,25...

[Page 88] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

88 Chapter 4:The /proc Filesystem WARNING Never attempt to tweak your kernel’s settings on a production system us- ing the various files in the /proc/sys directory. Occasionally, chang- ing a setting may render the kernel unstable, requiring a rebo...

[Page 89] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 89 or restarting a system, syncing all mounted filesystems, or dumping important information to your console. This feature is most useful when using a development kernel or if you are experiencing system freezes. For ...

[Page 90] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

90 Chapter 4:The /proc Filesystem 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, at least in the eyes of the kernel. If mul...

[Page 91] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 91 • super-max — Controls the maximum number of superblocks available. • super-nr — Displays the current number of superblocks in use. /proc/sys/kernel This directory contains a variety of different configurat...

[Page 92] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

92 Chapter 4:The /proc Filesystem • msgmnb — Sets the maximum number of bytes in a single message queue. By default, 16384. • msgmni — Sets the maximum number of message queue identifiers. By default, 16. • osrelease — Lists the Linux ker...

[Page 93] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 93 • rtsig-nr — The current number of POSIX realtime signals queued by the kernel. • sem — This file configures semaphore settings within the kernel. A semaphore is a System V IPC object that is used to contro...

[Page 94] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

94 Chapter 4:The /proc Filesystem The idea is that an attacker could bombard your system with requests that generate errors and fill up your logs or require all of your system’s resources to handle error logging. The settings in message_burst and m...

[Page 95] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 95 • ip_forward — Permits interfaces on the system to forward packets to one other. By default, this file is set to 0 to disable forwarding, but setting this file to 1 will enable forwarding. • ip_local_port_ran...

[Page 96] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

96 Chapter 4:The /proc Filesystem • buffermem — Allows you to control the percentage amount of total system memory to be used for buffer memory. Typical output for this file looks like this: 21060 The first and last values set the minimum and max...

[Page 97] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.3:Directories in /proc 97 • pagetable_cache — Controls the number of page tables that are cached on a per-processor basis. The first and second values relate to the minimum and maximum number of page tables to set aside, respectively. A...

[Page 98] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

98 Chapter 4:The /proc Filesystem Registered line disciplines are stored in the ldiscs file, with detailed information available in the ldisc directory. 4.4 Using sysctl Setting kernel parameters in the /proc/sys directory need not be a manual proces...

[Page 99] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

Section 4.5:Additional Resources 99 comprehensive guide to this information. Rather, you should definitely investigate additional sources of information about /proc before tweaking your kernel. 4.5.1 Installed Documentation Most of the best /proc doc...

[Page 100] Red Hat LINUX 7.2 - OFFICIAL LINUX CUSTOMIZATION GUIDE

100 Chapter 4:The /proc Filesystem ...