fduran

# get an email every time a user logs in through ssh
# www.fduran.com

# add in /etc/profile
echo "`whoami` logged in at `date` from `echo $SSH_CLIENT`" | mail -s "`hostname` login" youremail@example.com &

# note this is not fool-proof. For example the user can run remotely a command thru ssh without logging in

fduran

# better command line history: more commands kept, aggregate, add timestamp
# www.fduran.com

# add in /etc/profile

shopt -s histappend
HISTSIZE=10000
HISTTIMEFORMAT="%Y-%m-%d %H:%M:%S "
HISTCONTROL=ignoredups
PROMPT_COMMAND="history -a;history -c;history -r;$PROMPT_COMMAND"

fduran

# ssh without passwords, useful for unattended automatic scp/rsync-over-ssh copies etc
# www.fduran.com

# Create public key without password in origin server:
ssh-keygen -t dsa

# if ssh target port is not 22, add it (ex: -p 2020) in ssh-copy-id after 'ssh':
# nano /usr/bin/ssh-copy-id

# Upload public key to remote target server:

fduran

# Postfix mail server for sending messages only, not exposed to receive email
# www.fduran.com

mv /etc/postfix/main.cf /etc/postfix/main.cf.orig
echo "inet_interfaces = 127.0.0.1" > /etc/postfix/main.cf
/etc/init.d/postfix restart

fduran

# apache optimization with Google's mod_pagespeed
# www.fduran.com

# Page for mod_pagespeed : http://code.google.com/speed/page-speed/docs/using_mod.html
# Download from http://code.google.com/speed/page-speed/download.html :
cd /usr/local/src
wget https://dl-ssl.google.com/dl/linux/direct/mod-pagespeed-beta_current_i386.deb
apt-get -f install
dpkg -i mod-pagespeed-*.deb
#

fduran

Defending against Spam using Linux Postfix
www.fduran.com

0) Consider outsourcing mail service

1) Spamassassin: good in its time, it's past its useful life since there are better options and it's a CPU hog.

2) Use black list servers, like Spamhaus and Spamcop:

In Posfix configuration file /etc/postfix/main.cf append:

fduran

# Linux. Act upon an event in a log file
# www.fduran.com

apt-get upgrade; apt-get install inotify-tools

# create file myalert.sh:
# example finding Exception in tomcat log and sending email

#!/bin/bash
while inotifywait -e modify /path/to/file.log; do

fduran

# www.fduran.com
# Number of top 10 current TCP connections per IP
netstat -tan| grep -v 'LISTEN'| awk '{print $5}'| grep -v 'and' |grep -v 'Address' |cut -d':' -f1 |sort -n | uniq -c | sort -rn | head -n10

# Top 10 IPs in Apache log files
cd /var/log/apache2; for i in ./access.log*; do echo $i; cat $i | awk '{print $1}'| sort -n | uniq -c | sort -rn | head -n10; done

fduran

# www.fduran.com
# default permissions for web files and directories 

cd web_directory
find . -type d -exec chmod 775 {} \;
find . -type f -exec chmod 664 {} \;

fduran

# www.fduran.com
# replace in a file (index.php for example) links from relative <a href="/path to absolute <a href="http://example.com/

sed -i 's/href=\"\//href=\"http:\/\/example.com\//g' index.php