UNIX shell -- trick and experience (20090423)

UNIX -- trick and experience

        author: kirk waingrow   

        just a copy,please refer freely

       

chapter 1 system management

 

overview:
daily jobs automation
system modification

 

section 1  collect system messages
 # hostname
 # grep 'hostname' /etc/hosts | awk '{print $3}'
 # hostid
 # uname -a
 # dmesg
 # df

 

section 2 backup important files
 kernel files:/kernel;/unix or /vmunix
 password file:/etc/passwd
 group files:/etc/group
 host table:/etc/hosts
 filesystem table:/etc/fstab or /etc/vfstab
 sendmail config file:/usr/lib/sendmail.cf or /usr/lib/sendmail.fc or /usr/lib/sendmail.mc
 inetd config file:/etc/inetd.conf
 TTY setting files:/etc/inittab or /etc/ttytab or /etc/ttys
 start up scripts:/etc/init.d or /etc/rc#.d

 

section 3 routine work

 TZ={GMT|PST|EDT|...}-24 date + %d
 ##/bin/bash
 FILE = 'runme'
 if test 'TZ=PST-24 date + %d' = 1 ;then
 $FILE
 fi

 #!/usr/bin/perl
  
 use POSIX;
 
 @THE_DATE=localtime(time);
 ++ $ THE_DATE[3];
 if((localtime(POXIX::mktime(@THE_DATE)))[3]==1){
  exit 0; 
 }
 exit 1;

addition:cron/crontab can not judge whether today is the last day of the current month

reference:localtime tzset tzfile crontab

 

section 4 disable unnecessary daemon processes  

modify:/etc/inetd.conf file with rc file
after modification type command:kill -HUP inetd_PID and check the logfile:/var/adm/messages or /var/adm/SYYLOG

after modify the rc file,you must reboot immediately

addition:inetd inetd.conf rc

 

section 5 assuring daemon processes are running

addition:cron crontab ps test

 

section 6 use fuser instead of ps

 comparing the commands to get PID ,fuser is more reliable and quick than ps
 # fuser /bin/csh
 # fuser -k /bin/csh

addition:fuser ps kill

 

section 7 building disk swap partition quickly

 

section 8 using nohup command to keep processes running

 

section 9 redirect output to NULL device

 purge useless files

 

section 10 stoping users login

 modify /etc/passwd
 modify /etc/inetd.conf
 close network interface
 close the access of remote shell and telnet
  it needs /etc/nologin
  for example:add the section as below
  the system is down right now fo rroutin e maintenance and should be back online by 23:00 . please

check back at this time . thank you for your understanding . the unix admins .
 close the access of remote ftp
  /etc/users
  # cut -d":" -f1 /etc/passwd > /etc/users
  # ypcat passwd | cut -d":' -f1 > /etc/users

addition:inetd nologin users ypcat

 

section 11 quickly rewinding of tape

 # mt -f /dev/rmt/0cbn rewind
 # < /dev/rmt/0cbn
 # < $DLT ; tar cvf $DLT /usr/spool/mail;< $DLT

addition:mt

 

section 12 generating a set of continuous digits

 #!/bin/sh
 # the script name is count
 lo=$1;hi=$2

 while [ $lo -lt $hi ]
 do
  echo -n $lo" "
  lo='expr $lo + 1'
 done

 #!/bin/sh
 string="the quick brown fox jumped readlly high"
 for i in 'echo "5 6 7 8 9"'
 do
  echo $string | cut -c $i
 done

 #!/bin/sh
 string ="the quick brown fox jumped readlly high"
 for i in 'count 5 20' ### count is the script name above
 do
  echo $string | cut -c $i
 done