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slow response on linux centos dual home nic on a load balancer down stream smtp solution is echo 2 > /proc/sys/net/ipv4/conf/eth0/rp_filter echo 2 > /proc/sys/net/ipv4/conf/eth1/rp_filter echo 2 > /proc/sys/net/ipv4/conf/eth2/rp_filter also modify /etc/sysctl.conf # Controls source route verification (previously 1) net.ipv4.conf.default.rp_filter = 2  source: https://www.centos.org/forums/viewtopic.php?t=7775

http://serverfault.com/questions/583372/postfix-transport-relay-access-denied/583438?noredirect=1#583438 virtual_mailbox_maps=/etc/postfix/virtual_mailbox_maps.txt ------------------------------------------------------- for clamd and amavis as scanner, if there is a clamav permission error add both clamd to amavis group or vice verse also check permission try 755

Task : to email old users that they have exceeded 100m disk space The problem is that the folder where the user is deep inside 2 folders so "du" is used. tr is used to remove characters cut to get the coloumn http://stackoverflow.com/questions/11049748/how-to-cut-multiple-columns-from-several-files-and-print-the-ouput-to-different   cd /backup/home/virtual du -m --max-depth=2  | tr './' ' ' | cut -d' '  -f 1,4 | while read space user do    if [ $space -gt 100 ]                     then         mail -s "Your account is using over 100MB Disk Space" $user <<MAIL  $user: You are now using $space MB in your home directory. The only total amount of diskspace allowed is 100 MB. MAIL  fi done

Varnish web application accelerator homepage: https://www.varnish-cache.org Install the Varnish YUM Repository # rpm -Uvh http://repo.varnish-cache.org/redhat/varnish-3.0/el5/noarch/varnish-release-3.0-1.noarch.rpm Install Varnish web accelerator # yum install varnish Enable Varnish web accelerator at startup # chkconfig varnish on Basic default.vcl # vi /etc/varnish/default.vcl 1 2 3 4 5 6 7 8 9 10 # This is a basic VCL configuration file for varnish. See the vcl(7) # man page for details on VCL syntax and semantics. # # Default backend definition. Set this to point to your content # server. # backend default { .host = "127.0.0.1"; .port = "80"; } Start Varnish web accelerator # service varnish start You will now have a basic Varnish web accelerator running on port 8080 Top 5 Varnish commands varnishstat Provides all the info you need to spot cache misses and errors. varnishhist Provides a histogram view of cache hits/m...

 Centos 4 and dovecot 1 fail2ban from: http://www.webstershome.co.uk/content/fail2ban-block-unwanted-attacks Create the filter file "/etc/fail2ban/filter.d/dovecot-pop3imap.conf" and add [Definition] failregex = (?: dovecot: pop3-login|imap-login): (?:Authentication failure|Aborted login \(auth failed|Aborted login).*rip=(<HOST>),.* ignoreregex = note: the failregex may need changing to suit your system. now add the following to "/etc/fail2ban/jail.conf" [dovecot-pop3imap] enabled = true filter = dovecot-pop3imap action = iptables-multiport[name=dovecot-pop3imap, port="110,143,995,993,25,465,587"] sendmail-whois[name=dovecot-pop3imap, dest=root, sender=fail2ban@server.com] logpath = /var/log/maillog maxretry = 5 findtime = 600 bantime = 3600

echo "Enter string to be placed" read NEWSTRING echo "===================================" echo "string to be replaced is $OLDSTRING" echo "string to be placed is $NEWSTRING  " echo "===================================" oldstr=$OLDSTRING #string to be replaced newstr=$NEWSTRING #new string to be placed echo "Enter folder path where we will find the string" read FOLDERPATH ### grep oldstring and output it in grep_output.txt    STEP1 grep -rl $oldstr $FOLDERPATH > grep_output.txt ### since there might be spaces or special characters on filenames, use sed to enclose them with quote and output in  sed_output.txt  STEP2 #for i in `cat grep_output.txt` #do sed -e "s/'/'\\\\''/g;s/\(.*\)/'\1'/" grep_output.txt  > sed_output.txt #done for i in `cat grep_output.txt` do sed -i "s/$oldstr/$newstr/g" $i > sed_output_new_old_string.txt done ## NOTE ## # 2013 latest ## STEP 2 Seems not wo...

Created this simple script to email disk space usage. #!/bin/bash ## Email directory list if over quota BASE2=/home/vmail/mazaredo.com ## Check whole directory summary BASE=/home/vmail #50GB THRESHOLD=52428800 # out=$(du -s $BASE | cut -f1) # if [ $out -gt $THRESHOLD ] then  echo $out  du -h --max-depth=1 $BASE2 | mail -s "DISK USAGE EXCEEDED" postmaster@example.com else  echo "quota not reached" fi