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  1. Introduction
  2. Abbreviated Boot
  3. The Boot Process
  4. Startup and Run Levels
  5. Initialization Scripts
  6. Runlevel Scripts
  7. Login Process
  8. Bash Shell
  9. Filesystems
  10. LILO, Kernel and Root Filesystem
  11. The Kernel
  12. Passwords, Users, Groups, and Quotas
  13. The Environment
  14. The /etc/sysconfig directory
  15. The /proc filesystem
  16. Process Control
  17. Devices
  18. Daemons Services
  19. Inetd and Network Services
  20. Programs and Libraries
  21. Security and PAM
  22. The printer services
  23. Mouse support with gpm
  24. Mail
  25. News
  26. UUCP
  27. LDAP
  28. NFS and RPC
  29. Samba, NetBIOS, WINS, nmbd
  30. Identd (auth)
  31. Telnet and FTP
  32. Apache web server
  33. DNS and named
  34. How X Works
  35. X Scripts
  36. Support for Text
  37. Keymapping for Programs
  38. Keycode Table
  39. Example Keymap File
  40. Terminfo Commands
  41. VT100 ESC sequences
  42. Kernel Revisited
  43. Configuration Files
  44. Credits

Linux Services, Devices, and Deamons

Linux Startup Services:

Startup services are services run at boot time. They may be provided by daemon programs running in the background or are one time only programs run during the bootup to provide some function to the system. This section gives a brief overview of these services. This section outlines those services that can be started using Redhat's linuxconf program. Not all are necessarily daemon programs. Also it is possible to set up other startup programs, daemons, or services that are not included in this list. There are 3 basic categories to these services.

  • A one time only program run at bootup to provide a function to the system such as kudzu, or keytable.
  • A program run as a daemon upon startup that provides system services such as gpm, autofs, cron, and atd.
  • A program run as a daemon upon startup that provides networking services such as dhcpd, bootparamd, arpwatch, gated, and httpd.
amdRuns the automount daemon for remote filesystem mounting such as nfs.
apmdMonitors battery status and can shut down the system if power is low.
arpwatchKeeps track of ethernet IP address parings what are resolved using the ARP protocol. This allows system administrators to note new IP addresses being used. It maintains a database in /var/arpwatch/arp.dat.
atdRuns commands scheduled by the "at" program at their scheduled times. Jobs are stored in /var/spool/at
autofsAlso called the automount daemon, it is used to automatically mount filesystems on demand. It is especially worthwhile for working with removeable media such as floppies or CD ROM disks.
bootparamdAllows remote computers to boot from a Linux box using the BOOTP network protocol. This allows the remote computer to get its IP address if the server knows the hardware address of the remote machine. The DHCP protocol is an upgrade to this protocol since it is more automated.
crondA daeman that executes scheduled commands according to the /etc/crontab file. It can be used to clean up temporary files in /tmp and /var/tmp and other places.
dhcpdProvides DHCP services to "lease" out IP addresses to remote machines.
gatedProvides routing services for BGP and other protocols. Alternative to routed. Supports IGP (Interior gateway protocol) and EGP (Exterior Gateway Protocol).
gpmProvides mouse support to Linux.
httpdThe Apache hypertext transfer protocol Web server.
identdServer implementing the TCP/IP proposed standard IDENT user identification protocol in RFC 1413. It returns user information to a remote host that a user is requesting a service from. Also called auth.
inetThe internet super daemon (inetd) that provides all the services specified in /etc/inetd.conf.
inndThe Usenet news server
isdnProvides ISDN (networking interface) services. See the isdnctrl man page for more information. The isdnctrl program is used to set up isdn interfaces. Pertinent files are /etc/sysconfig/activeisdn, /dev/isnnctrl, /etc/sysconfig/provider, and /var/log/isdn.log.
keytableLoads the appropriate keyboard map from /etc/sysconfig/keyboard. This does not set up a daemon program to reside in the background, but just loads the keyboard keytable and the system font.
kudzuDetects and configures new or changed hardware on a system. This program is run once when the system boots and does not run as a daemon in the background.
ldapLightweight directory access protocol package which provides client/server based directory database services which runs on UNIX platforms over TCP/IP. RFC is 1777.
linuxconfAccording to Redhat it is a post startup hook for linuxconf. It does not run as a daemon.
lpdProvides printing services to Linux. It is a print spooler daemon.
mars-nweLoads the MARS Netware compatible file and print server daemon called nwserv. Allows a Linux machine to be used as a file and printserver for netware based clients using IPX/SPX.
mcservAllows users on remote machines to use the midcommander file manager to work with files. It uses the PAM library for authentication.
namedProvides DNS services. It is a name server used to translate local IP addresses to names and vice-versa.
netfsMounts and unmounts Network Fils System (NFS), Windows (SMB), and Netware (NCP) file systems. The mount command is used to perform this operation and no daemon is run in the background.
networkBrings up all the network interfaces under the directory /etc/sysconfig/network-scripts. Also controls IP_forwarding and IP_defrag.
nfsProvides Network File System server services
nfslockNFS file locking service. Starts the daemons rpc.locked and rpc.statd. The rpc.statd daemon implements the Network Status Monitor (NSM) RPC protocol which is a reboot notification service used to implement file lock recovery when an NFS server crashes and reboots.
nscdThe name switch cache daemon. which handles password and group lookups for running programs and caches the information for the next query. Normally this daemon is used to support NIS.
pcmciaProvides access to PCMCIA (PC Cards) services configured in the /etc/exports file.
portmapProvides Remote Procedure Call (RPC) support for other protocols like NFS.
postgresqlRuns the postgres database and provides SQL services. It runs the daemon postmaster.
pulseHeartbeat daemon for monitoring the health of lvs (Redhat clustering services) cluster nodes. This tool is used for clustering machines.
pxeA preboot execution environment (PXE) server. Allows network boot of other PXE machines. PXE is a standard developed by Intel for a means of booting various operating systems on remote machines.
randomSaves and restores a random value used to generate better random numbers for security. No daemon program is invoked for this operation.
routedProvides for automatic router table updates using the RIP dynamic routing information protocol.
rstatdThe rstat protocol allows users on a network to get performance information for any machine on the network. Runs the rpc.rstatd daemon which provides performance statistics retrieved from the kernel usually by using the "rup" command.
rusersdProvides services that allow users to find one another over the network.
rwalldProvides users with an ability to use the rwall command to write messages on remote terminals.
rwhodThe rwho protocol lets remote users get a list of all users logged onto a machine by running the rwho daemon.
sendmailThe sendmail mail transport agent daemon used to move e-mail from one machine to another.
smbProvides SMB (Samba) client/server services which include file and print services. It allows Linux computers to exchange file and printer services with Microsoft Windows based systems.
snmpdProvides Simple Network Management Protocol support to Linux.
squidRuns the squid proxy web server
syslogSystem logging daemon which records system events to log files usually in the directory "/var/log". The actual name of the daemon is klogd.
xfsX font file server
xntpdStarts the Network Time Protocol NTPv3 daemon. NTP provides a means to synchronize time and coordinate time distribution in a large, diverse internet operating at all speeds. RFC 1305 describes this protocol.
ypbindBinds YP/NIS clients to a yellow pages server. NIS (Network Information Service) is a name service created by Sun.
yppasswddAllows users to change their passwords on systems running YP/NIS
ypservThis daemon provides the YP/NIS (Network Information System) server functions.

Linux Deamons

This section gives a brief overview of miscellaneous daemons (not covered in the paragraph on services) running on the system and their function.

initThe first process to start after the kernel. It controls the system runlevel and adapts any child whose parent dies.
nmbdResponds to netbios name service requests for Samba works in conjunction with Samba which is why it is not mentioned under startup services..
update (kupdate)Does a sync every 30 seconds. A sync is an updating of memory pages, or virtual memory pages that have been changed, but not saved to the swap disk
bdflush (kflushd)Started by update - does a more imperfect sync more frequently
gettyListens for connections at terminals