Bash

It happen to me all the time that one of developers notifies me about some kind of problem that I can’t confirm from my account. Sometimes it was because of bad ssh keys configuration, other times file permissions, mostly such stuff. It’s sometimes convenient to “enter into someone’s shoes” to see what’s going on there. If you’re root on machine you may do that like this: Switch to developer user su developer - Easy one but that’s not enough for all cases. When you use bastion host (or similar solutions) sometimes users have connection problems and it’s harder to check. When such user have ForwardAgent ssh option enabled you may stole this session to check login problems. ...

Virtualenvs in python are cheap but from time to time you will install something with pip on your system and when time comes removing all this crap could be difficult. I found this bash snippet1 that will uninstall package with all dependencies: Recursive pip uninstall for dep in $(pip show python-neutronclient | grep Requires | sed 's/Requires: //g; s/,//g') ; do pip uninstall -y $dep ; done pip uninstall -y python-neutronclient Depending how you installed it, you might need to use sudo. ...

When you deploy your application in cloud you don’t need and don’t want your hosts exposed via SSH to the world. Malware scans whole network for easy SSH access and when find something will try some brute force attacks, overloading such machines. It’s easier to have one exposed, but secured host, that doesn’t host anything and is used as proxy/gateway to access our infrastructure- it’s called bastion host  external link . ...

Sometimes it’s easier to use octal file permissions but they’re not so easy to list. I caught myself few times that I didn’t remember how to list them - so this is a reason for that note. stat -c "%a %n" * 755 bin 755 games 755 include Yes, it’s that easy 😃 And here also with human readable attributes: stat -c '%A %a %n' * drwxr-xr-x 755 bin drwxr-xr-x 755 games drwxr-xr-x 755 include

I’m playing a lot with Docker lately. Building images, and then rebuilding, and then building again… It’s pretty boring. To automate this task a little I used inotify to build automatically after I changed any file. This trick could be used in many different situations. On Linux You will need inotify-tools package: Install inotify-tools on Linux sudo apt-get install -y inotify-tools Then run something like this: ...

I never tried it before but today I needed to install WordPress… From command line only. And there is a way to do this with wp-cli  external link . WP-CLI installation First some requirements (as root): apt-get install php5-cli php5-mysql mysql-client curl And now installation of wp-cli (as root too): curl -O https://raw.githubusercontent.com/wp-cli/builds/gh-pages/phar/wp-cli.phar chmod +x wp-cli.phar mv wp-cli.phar /usr/local/bin/wp Check if it’s working: ...

Sometimes deployment process or other heavy task may cause some Nagios checks to rise below normal levels and bother admin1. If this is expected and you want to add downtime on host/service during this task you may use this script: #!/bin/bash function die { echo $1; exit 1; } if [[ $# -eq 0 ]] ; then die "Give hostname and time in minutes as parameter!" fi if [[ $# -eq 1 ]] ; then MINUTES=15 else MINUTES=$2 fi HOST=$1 NAGURL=http://nagios.example.com/nagios/cgi-bin/cmd.cgi USER=nagiosuser PASS=nagiospassword SERVICENAME=someservice COMMENT="Deploying new code" export MINUTES echo "Scheduling downtime on $HOST for $MINUTES minutes..." # The following is urlencoded already STARTDATE=`date "+%d-%m-%Y %H:%M:%S"` # This gives us the date/time X minutes from now ENDDATE=`date "+%d-%m-%Y %H:%M:%S" -d "$MINUTES min"` curl --silent --show-error \ --data cmd_typ=56 \ --data cmd_mod=2 \ --data host=$HOST \ --data-urlencode "service=$SERVICENAME" \ --data-urlencode "com_data=$COMMENT" \ --data trigger=0 \ --data-urlencode "start_time=$STARTDATE" \ --data-urlencode "end_time=$ENDDATE" \ --data fixed=1 \ --data hours=2 \ --data minutes=0 \ --data btnSubmit=Commit \ --insecure \ $NAGURL -u "$USER:$PASS"| grep -q "Your command request was successfully submitted to Nagios for processing." || die "Failed to con tact nagios"; echo Scheduled downtime on nagios from $STARTDATE to $ENDDATE Threat this script as template with some tips: ...

On Debian in default installation you have different configuration files for PHP in Apache, FPM, CLI, etc. But on CentOS you have only one php.ini for all of them. In case I have, I need to have different configuration file for scripts running in CLI mode (more memory, etc). I could run it like this: php -c /etc/php-cli.ini script.php But this a little burdensome. So I do it like this: ...

Everybody knows passwd command but it’s useless when you need to change ex. root password from command line without waiting for input. In such case oneliner below could help: echo "root:new_password" | chpasswd

I had quite simple task - compare two lists of hosts and check if hosts from first one are also on the second one. I started with diff: diff -u biglist.txt hosts_to_check.txt | grep -E "^\+" It was fine but output needs some filtering to get what I want. I’ve found another example with grep: grep -Fxv -f biglist.txt hosts_to_check.txt | sort -n This will search for all lines in hosts_to_check.txt which don’t match any line in biglist.txt. So after this I’ve got list of hosts that I have to check. That’s exactly what I need 😄