SYSTEM SERVICES (DAEMONS)

SYSTEM SERVICES (DAEMONS)
The system services can be classified into 2 types: /etc/xinetd.d based & /etc/rc.d/init.d based services.
/etc/xinetd.d --based services are

telnet finger imap ipop2 ipop3
pop3s rlogin rsh sgi_fam
the executable daemons of these services are at /etc/rc.d/init.d, named xinetd

/etc/rc.d/init.d – based services are
apmd autofs dhcpd halt httpd
iptables kudzu named network nfs
portmap sendmail snmpd smb ssh
squid vncserver vsftpd xinetd ypbind
ypserv zebra

 apmd automatic power management daemon
 autofs automatic file system
 dhcpd dynamic host configuring protocol daemon
 httpd hyper text transfer protocol daemon
 iptables for fire wall security
 kudzu enabling plug and play facility
 named for bind (DNS-Domain Name System) server
 nfs network file system
 portmap services that starts when n/w is enabled
 sendmail used for mail server application
 snmpd simple n/w management protocol
 smb samba server (Linux/windows connectivity)
 ssh secure shell daemon
 squid proxy server
 vncserver remote desktop sharing
 vsftpd very secure file transfer protocol daemon
 xinetd enable /etc/xinetd.d services
 ypbind NIS(n/w info server) client
 ypserv NIS server
 zebra used for routing.

Ways of enabling these services:-
chkconfig enabling a service this way keeps a service enabled until next restart.
#chkconfig - -list service_name displays the current run level of that service.
#chkconfig service_name on/off used to enable/disable a particular service
#chkconfig - -levels 35 service_name on enables that service on run levels 3,5


Run control script resides in /etc/rc.d contains script files for rc0 to rc6. [the script file starting with ‘S’ represents the scripts to be start-up during next system boot and the script starting with K represents the stopped scripts].

#ntsysv cmnd used to enable or disable a service during next start up too.

Enable Services

#/etc/rc.d/init.d/service-name start/stop/restart/reload/status
OR
#service service-name start/stop/restart/reload/status

Configuring a YUM Repository
-------------------------------

Steps:

Make sure ftp server package is selected while installing the m/c in which we are planning to create a yum repository.


Copy all rpms from the corresponding directory on RHEL DVD to somewhere under /var/ftp/ say /var/ftp/pub/Server

install createrepo rpm which is inside the rhel dvd

#createrepo /var/ftp/pub/Server

that's all yum repository is ready to use.

To make it available for other machines in the network via ftp

#/etc/init.d/vsftpd start
#chkconfig vsftpd on

On client machines
let our yum repository is available at 192.168.0.254

#cd /etc/yum.repos.d/
#cat > test.repo
[first repo]
name= my first repo
baseurl=ftp://192.168.0.254/pub/Server
enabled=1
gpgcheck=0

ctrl+c

#yum list all

To check whether a package is installed or not

#rpm -qa | grep -i

To install something using YUM

#yum install

/etc more tremcap
Etc less termcap
Find -name
Find -perm 700
Find - uid 500
Find –size

Ln -s --------soft link
Ln ----------hard link


Umask –S | umask in symbolic form
Find –print | grep xorg.conf

Environmental Variables $PATH $DISPLAY $PS1 $TERM $USER $HOME $SHELL

Set command shows all the variables

PATH=$PATH:/root