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.The rest of the steps are exactly as they are shownabove.This should allow you to boot into single-user mode so you can re-editinittabto its previ-ous value.Next, we will discuss information in the files within the /etc/sysconfig/directory whichdefine the parameters used by different system services when they start up.3.3.Sysconfig InformationThe following information outlines some of the various files in the /etc/sysconfig/ di-rectory, their function, and their contents.This information is not intended to be complete,as many of these files have a variety of options that are only used in very specific or rarecircumstances. 64 Chapter 3.Boot Process, Init, and Shutdown3.3.1.Files in the/etc/sysconfig/ DirectoryThe following files are normally found in/etc/sysconfig/:" amd" apmd" arpwatch" authconfig" cipe" clock" desktop" dhcpd" firewall" gpm" harddisks" hwconf" i18n" identd" init" ipchains" iptables" irda" keyboard" kudzu" mouse" named" netdump" network" ntpd" pcmcia" radvd" rawdevices" redhat-config-users" samba" sendmail" soundcard" squid" tux" ups" vncservers Chapter 3.Boot Process, Init, and Shutdown 65" xinetdIt is possible that your system may be missing a few of them if the corresponding programthat would need that file is not installed.Next, we will take a look at each one.3.3.1.1./etc/sysconfig/amdThe /etc/sysconfig/amd file contains various parameters used by amd allowing for theautomounting and automatic unmounting of filesystems.3.3.1.2./etc/sysconfig/apmdThe /etc/sysconfig/apmd file is used by apmd as a configuration for what things tostart/stop/change on suspend or resume.It is set up to turn on or off apmd during startup,depending on whether your hardware supports Advanced Power Management (APM) or ifyou choose not to use it.apm is a monitoring daemon that works with power managementcode within the Linux kernel.It can alert you to a low battery if you are using Red HatLinux on a laptop, among other things.3.3.1.3./etc/sysconfig/arpwatchThe /etc/sysconfig/arpwatchfile is used to pass arguments to the arpwatch daemon atboot time.Thearpwatchdaemon maintains a table of Ethernet MAC addresses and their IPaddress pairings.For more information about what parameters you can use in this file, typeman arpwatch.By default, this file sets the owner of thearpwatchprocess to the userpcap.3.3.1.4./etc/sysconfig/authconfigThe/etc/sysconfig/authconfigfile sets the kind of authorization to be used on the host.It contains one or more of the following lines:" USEMD5= value , where value is one of the following:" yes MD5 is used for authentication." no MD5 is not used for authentication." USEKERBEROS= value , where value is one of the following:" yes Kerberos is used for authentication." no Kerberos is not used for authentication." USELDAPAUTH= value , where value is one of the following:" yes LDAP is used for authentication." no LDAP is not used for authentication. 66 Chapter 3.Boot Process, Init, and Shutdown3.3.1.5./etc/sysconfig/clockThe /etc/sysconfig/clockfile controls the interpretation of values read from the systemclock.Earlier releases of Red Hat Linux used the following values (which are deprecated):" CLOCKMODE= value , where value is one of the following:" GMT Indicates that the clock is set to Universal Time (Greenwich Mean Time)." ARC Indicates the ARC console s 42-year time offset is in effect (for Alpha-based sys-tems only).Currently, the correct values are:" 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 thatit is set to local time." ARC= value , where value is the following:" true Indicates the ARC console s 42-year time offset is in effect.Any other valueindicates that the normal UNIX epoch is assumed (for Alpha-based systems only)." ZONE= filename Indicates the timezone file under /usr/share/zoneinfo that/etc/localtimeis a copy of, such as:ZONE="America/New York"3.3.1.6./etc/sysconfig/desktopThe/etc/sysconfig/desktopfile specifies the desktop manager to be run, such as:DESKTOP="GNOME"3.3.1.7./etc/sysconfig/dhcpdThe /etc/sysconfig/dhcpd file is used to pass arguments to the dhcpd daemon at boottime.Thedhcpddaemon implements the Dynamic Host Configuration Protocol (DHCP) andthe Internet Bootstrap Protocol (BOOTP).DHCP and BOOTP assign hostnames to machineson the network.For more information about what parameters you can use in this file, typeman dhcpd.3.3.1.8./etc/sysconfig/firewallThe/etc/sysconfig/firewallfile contains various firewall settings.By default, this file isempty. Chapter 3.Boot Process, Init, and Shutdown 673.3.1.9./etc/sysconfig/gpmThe /etc/sysconfig/gpm file is used to pass arguments to the gpm daemon at boot time.The gpm daemon is the mouse server which allows mouse acceleration and middle-clickpasting.For more information about what parameters you can use in this file, typeman gpm.By default, it sets the mouse device to/dev/mouse.3.3.1.10./etc/sysconfig/harddisksThe /etc/sysconfig/harddisks file allows you to tune your hard drive(s).You can alsouse/etc/sysconfig/hardiskhd[a-h], to configure parameters for specific drives.WarningDo not make changes to this file lightly.If you change the default values stored here, you could corruptall of the data on your hard drive(s).The/etc/sysconfig/harddisksfile may contain the following:" USE_DMA=1, where setting this to 1 enables DMA.However, with some chipsets and harddrive combinations, DMA can cause data corruption.Check with your hard drive documen-tation or manufacturer before enabling this." 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 cau-tion." EIDE_32BIT=3enables (E)IDE 32-bit I/O support to an interface card." LOOKAHEAD=1enables drive read-lookahead." EXTRA_PARAMS=specifies where extra parameters can be added.3.3.1.11./etc/sysconfig/hwconfThe/etc/sysconfig/hwconffile lists all the hardware thatkudzudetected on your system,as well as the drivers used, vendor ID and device ID information.Thekudzuprogram detectsand configures new and/or changed hardware on a system.The /etc/sysconfig/hwconffile is not meant to be manually edited.If you do edit it, devices could suddenly show up asbeing added or removed.3.3.1.12./etc/sysconfig/i18nThe/etc/sysconfig/i18nfile sets the default language, such as:LANG="en_US"3.3.1.13./etc/sysconfig/identdThe /etc/sysconfig/identdfile is used to pass arguments to the identd daemon at boottime.Theidentddaemon returns the username of processes with open TCP/IP connections.Some services on the network, such as FTP and IRC servers, will complain and cause slowresponses if identd is not running.But in general, identd is not a required service, so if 68 Chapter 3.Boot Process, Init, and Shutdownsecurity is a concern, you should not run it.For more information about what parametersyou can use in this file, typeman identd.By default, the file contains no parameters.3.3.1.14
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