Print the total bytes of files in a directory grouped by date
ls -l|awk ‘length($6)==3{x[$6″ “$7]+=$5};END{for(i in x)printf”%s:\t%d\n”,i,x[i]}’
Reset the mysql root password
Stop the mysql daemon Restart mysql using the command mysqld_safe –skip-grant-tables Now you should be able to connect as root Once connected run the following: update user set Password=PASSWORD(‘new-password’) where user=’root’; then flush privileges exit mysql restart mysql and you should be able to login with the new password
Remove top navbar from wordpress
Edit wp-includes/functions.php and add the following add_action(‘after_setup_theme’, ‘remove_admin_bar’); function remove_admin_bar() { if (!current_user_can(‘administrator’) && !is_admin()) { show_admin_bar(false); } } Now the top navbar will only showup for admin users.
Find the largest file in a directory tree
find /path -type f -exec ls -s {} \; | sort -n | tail -1
Compress the contents current directory, but compress the smallest files first
ls -s | awk NR!=1 | sort -n | awk ‘{print $2}’ | xargs bzip2 -9v
Using netstat
netstat -ntulp displays everything that is listening tcp and udp and the ip that it is listening on
View network traffic (by port number)
To view web traffic (for example) use tcpdump -s 0 -w – port 80 | tcpdump -r – -A
Filter duplicate lines from a sorted files
cat list-1 list-2 list-3 | sort | uniq > final.list
Debugging bash scripts
Debugg bash scripts by runing with option -x example bash -x scriptname.sh
lowercase filen names
#! /bin/bash DIR=$1 for a in `ls $DIR` do fname=`echo $a | tr A-Z a-z` mv $DIR/$a $DIR/$fname done; exit 0
Linux Security
“Yes, I’m paranoid — but am I paranoid enough?” ― David Foster Wallace, Infinite Jest Hardening Public Servers Install system accounting On Debian based systems run ‘apt-get install acct’ then you can use commands lastcomm and sa to see who ran various comands. Also a log file will be writen to /var/log/account/pacct Remove compilers from production severs use the command ‘apt-get –purge remove gcc’ Setup remote logging See http://www.thegeekstuff.com/2012/01/rsyslog-remote-logging/ to find out how Install fail2ban Linux.com has a good intro to fail2ban http://www.linux.com/learn/tutorials/469597-weekend-project-keep-out-repeat-offenders-with-fail2ban-on-linux
bashprofile
# .bash_profile # Get the aliases and functions if [ -f ~/.bashrc ]; then . ~/.bashrc fi # User specific environment and startup programs PATH=$PATH:$HOME/bin:/sbin export JAVA_HOME=/usr/java/jdk1.6.0_05/bin/java export PATH=$PATH:/usr/java/jdk1.6.0_05/bin export HISTIGNORE=”&” export EDITOR=nano export PATH unset USERNAME alias rm=’rm -i’ alias cp=’cp -i’ alias ls=’ls –color’ alias zf=’zf.sh’ echo -e “\033[36m########################## \033[0m” echo -e “\033[36mServer $HOSTNAME \033[0m” echo -e “\033[36mWelcome back $USER \033[0m” echo -e “\033[36musers loggged in: \033[0m” echo -e “\033[36m `users ` \033[0m” echo -e “\033[36m`uptime` \033[0m” echo […]
bashrc
Here is my typical .bashrc file # .bashrc # Source global definitions if [ -f /etc/bashrc ]; then . /etc/bashrc fi # append commenads to bash_history (when using more then one window) shopt -s histappend PROMPT_COMMAND=’history -a’ # User specific aliases and functions PATH=$PATH:$HOME/bin:/sbin #export JAVA_HOME=/usr/java/jdk1.6.0_05/bin/java export HISTIGNORE=”&” export EDITOR=nano export PATH unset USERNAME #function PWD { #pwd | awk -F\/ ‘{print $(NF-1),$(NF)}’ | sed ‘s/ /\\//’ #} #export PS1=”\[\033[0;32m\]\u@\h \[\033[33m\]\$(pwd 3)\[\033[0m\] \$ “;
apache – watch httpd for connected clients
watch httpd for connected clients watch “netstat -anpt | grep httpd | grep ESTABLISHED|cut -b45-60 | cut -d’:’ -f1 | sort” OR netstat -plan|grep :80|awk {‘print $5’}|cut -d: -f 1| sort|uniq -c | sort -nk 1