Archive for the ‘Bash’ Category
Recently I was presented with the following situation at work:
- Your input is a handful of directories, filled with files, some of them are a “sort of a copy” of the other
- Your output should be one directory with all the files from the source directories merged into it
- The caveat is – if any of the files collide, you must mark them somehow for inspection
So that sounds pretty simple, isn’t it? In my case the input was millions of files. I’m not sure about the exact number, it doesn’t matter. The best solution for this problem is to never get to this situation, however sometimes you just inherit stuff like that at a new work place.
The Solution
We needed a ninja. I called it ninja-merge.sh. It is a Bash wrapper for rsync that will merge directories one by one into a destination directory and handle the collisions for you using a checksum function (md5 was “good enough” for that task).
Get ninja-merge.sh here:
https://github.com/danfruehauf/Scripts/tree/master/ninja-merge
It even has unit tests and the works. All that you have to do is specify:
- A list of source directories
- A destination directory
- A directory to store the collisions
If a path collided, you might end up with something like that in your collision directory:
$ cd collision_directory && find . -type f
./a/b/filename1.nc.345c3132699d7524cefe3a161859ebee
./a/b/filename1.nc.259974c1617b40d95c0d29a6dd7b207e
Sorting the collisions is something you’ll have to do manually. Sorry!
Every so often I come across Bash scripts which are written as if Bash is a pile of rubbish and you just have to mould something ugly with it.
True, Bash is supposedly not the most “powerful” scripting language out there, but on the other hand if you’re using traditional methods then you can avoid installing gazillion ruby gems or perl/python modules (probably not even using RPM or DEB!!) just to configure your system. Bash is simple and can be elegant. But that’s not the point.
The point is that too often Bash scripts which people write have zero maintainability and readability. Why is that??
I’m not going to point at any bad examples because that’s not a very nice thing to do, although I can and easily.
Please do follow these three simple guidelines and you’ll get 90% of the job done in terms of maintainability and readability:
- Functions – Write code in functions. Break your code into manageable pieces, like any other programming language, ey?
- Avoid global variables – Global variables just make it all too complicated to follow what’s going on where. Sometimes they are needed but you can minimize the use of them.
- INDENTATION – INDENT YOUR BLOODY CODE. If you have an if or for or what not, please just indent the block under it. It’s that simple and makes your code so much more readable.
That was my daily rant.
My Bash coding (or scripting) conventions cover a bit more and can be found here:
https://github.com/danfruehauf/Scripts/tree/master/bash_scripting_conventions
Say you have a Nagios system monitoring everything already in your system and in addition to that you have a Graylog2 installation which parses logs from anywhere and provides you with invaluable feedback on what’s really going on in your system.
And then comes the problem, or one of them:
- Graylo2 is not really good in sending alerts (or maybe it is?)
- Nagios is already configured to send alerts and you would like to use the same contact groups for instance
The solution is below.
Design
Before making you read through the whole blog entry, I’ll just outline the solution I’ve chosen to implement and you can decide whether it’s good for you or not. Here it is in a nutshell:
- An alert is being generated in Graylo2 in a configured stream
- Graylog2 will use exec callback plugin to call an external alerting command, call it graylog2-alert.sh for instance
- graylog2-alert.sh will push an alert using send_ncsa
- Nagios parses the alert and notifies whoever is subscribed on that service
Pretty simple and bullet proof.
Graylog2 Configuration
I assume you already have Graylo2 fully configured, in this case download the wonderful exec callback plugin and place it under the plugin/alarm_callbacks directory (under the Graylog2 directory obviously).
Login to Graylog2 and enable under Settings->System the Exec alarm callback.
Click configure and point it to /usr/local/sbin/graylog2-alert.sh
That’s it for now on the Graylog2 interface side.
NSCA – Nagios Service Check Acceptor
Properly configure NSCA to work in your nagios configuration. That means usually:
- Opening port 5667 (or another port) on your nagios server
- Choosing a password for symmetrical encryption on the nagios server and the NSCA clients
- Starting the nsca daemon on the nagios server, so it will accept NSCA communications
Generally speaking configuring NSCA is out of the scope of this article and more information can be found here:
http://www.nsclient.org/nscp/wiki/doc/usage/nagios/nsca
That said, I’ll just mention that when everything works, you should be able to run successfully:
echo "HOSTNAME;SERVICE;2;Critical" | send_nsca -d ';' -H NAGIOS_HOSTNAME
graylog2-alert.sh
On the Graylog2 host, place the following file under /usr/local/sbin/graylog2-alert.sh:
#!/bin/bash
# nagios servers to notify
NAGIOS_SERVERS="NAGIOS_SERVER_1 NAGIOS_SERVER_2 NAGIOS_SERVER_3"
# add a link to the nagios message, so it's easy to access the interface
# on your mobile device once you get an alert
GL2_LINK="http://GRAYLOG_URL/streams"
main() {
local tmp_file=`mktemp`
local gl2_topic=`echo $GL2_TOPIC | cut -d'[' -f2 | cut -d']' -f1`
echo `hostname`";Graylog2-$gl2_topic;2;$GL2_LINK $GL2_DESCRIPTION" > $tmp_file
local nagios_server
for nagios_server in $NAGIOS_SERVERS; do
/usr/sbin/send_nsca -d ';' -H $nagios_server < $tmp_file
done
rm -f $tmp_file
}
main "$@"
This in combination of what we did before will fire alerts from Graylo2 -> exec callback plugin -> graylog2-alert.sh -> NSCA -> nagios server.
The nagios side
All you have left to do now is to define services for use with Graylog2 alerts. It is a rather straight forward service configuration for nagios, here is mine (generated puppet in case you wonder):
define service {
service_description Graylog2-STREAM_NAME
host REPLACE_WITH_YOUR_GRAYLOG2_HOST
use generic-service
contact_groups Graylog2-STREAM_NAME
passive_checks_enabled 1
max_check_attempts 1
# enable active checks only to reset the alarm
active_checks_enabled 1
check_command check_tcp!22
normal_check_interval 10
notification_interval 10
# set the contact group
contact_groups Graylog2-STREAM_NAME
flap_detection_enabled 0
}
define contactgroup{
contactgroup_name Graylog2-STREAM_NAME
alias Graylog2-STREAM_NAME
members dan
}
We usually have a contact group per Graylog2 stream. We just associate developers with the topic that’s relevant to them.
Restart your nagios and you’re set. Don’t forget to also start nsca!!
Resetting the alert
Graylog2 and NSCA will never generate “positive” OK alerts, but only critical ones. So you need a mechanism to reset the alert every once in a while. If you will scroll up you will see that I check port 22 (SSH) on the Graylog2 host.
How often you ask?
When configuring a new stream in Graylog2, it is best if you match the Grace period in Graylog2 to the normal_check_interval in nagios. Which would guarantee the alert will be reset before a new one comes in.
Puppet
The whole shenanigans is obviously puppetized in our environment. Tailoring nagios to an environment is usually very different between environments so I have decided it is rather redundant to paste puppet recipes altogether.
I hope you can find this semi-tutorial helpful.
Since I got this question from way too many people, I wanted to just share my “cross distribution” and “cross desktop environment” way of doing that very simple thing of enabling a Hebrew keyboard layout under Linux.
Easy As
After logging into your desktop environment, type this:
setxkbmap -option grp:switch,grp:alt_shift_toggle,grp_led:scroll us,il
Alt+Shift will get you between Hebrew and English. Easy as.
Sustainability
Making it permanent is just as easy:
mkdir -p ~/.config/autostart && cat <<EOF > ~/.config/autostart/hebrew.desktop
[Desktop Entry]
Encoding=UTF-8
Name=Hebrew
Comment=Enable a Hebrew keyboard layout
Exec=setxkbmap -option grp:switch,grp:alt_shift_toggle,grp_led:scroll us,il
EOF
Should sustain logout/login, reboots, reinstalls (as long as you keep /home on a different partition), distribution changes and choosing a different desktop environment (KDE, GNOME, LXDE, etc.).
The Assignment
You have a directory with gazillion files. Since most filesystems are not very efficient with many files in one directory, it is advisable to spread them among a hierarchy of directories. Write a program (or script) which handles a directory with many files and spreads them in an efficient hierarchy.
Does that sounds like a University assignment or something? Yes, it does.
Well apparently such a situation just happened to me in real life. Searching across the internet I couldn’t find anything too useful. And I will stand corrected if there is something which already deals with that problem. Post ahead if so.
And yes, thank god I’m using Unix (Linux), don’t even want to think what one would do on Windows.
The Situation
An application was spooling many files to the same directory, generating up to a million files in the same directory. I’m sorry I cannot disclose any more information about it, but lets just say it is a well known open source application.
Access to these files was obviously fast having ext4 and dir_index, but the directory index is too big to actually list files or do anything else without clogging everything in the system. And we need these files.
So we’ve decided to model the files in a way that’ll be more efficient for browsing and we can then handle it from there.
The Solution
After implementing something pretty quick and dirty for the situation, to mitigate the pain, I’ve sat down and wrote something a bit more generic. I’m happy to introduce the spread_files.sh utility.
What does it take care of:
- Reading the directory index just once
- Hierarchy depth as parameter
- Stacking up to X files per mv command
- Has recursion in Bash!!
Obviously the best solution would be to never get to that situation, however if you do, feel free to use spread_files.sh.
I personally have a numerous number of hosts which I sometimes have to SSH to. It can get rather confusing and inefficient if you get lost among them.
I’m going to show you here how you can get your SSHing to be heaps more efficient with just 5 minutes of your time.
.ssh/config
In $HOME/.ssh/config I usually store all my hosts in such a way:
Host host1
Port 1234
User root
HostName host1.potentially.very.long.domain.name.com
Host host2
Port 5678
User root
HostName host2.potentially.very.long.domain.name.com
Host host3
Port 9012
User root
HostName host3.potentially.very.long.domain.name.com
You obviously got the idea. So if I’d like to ssh to host2, all I have to do is:
ssh host2
That will ssh to root@host2.potentially.very.long.domain.name.com:5678 – saves a bit of time.
I usually manage all of my hosts in that file. Makes life simpler, even use git if you feel like it…
Auto complete
I’ve added to my .bashrc the following:
_ssh_hosts() {
local cur="${COMP_WORDS[COMP_CWORD]}"
COMPREPLY=()
local ssh_hosts=`grep ^Host ~/.ssh/config | cut -d' ' -f2 | xargs`
[[ ! ${cur} == -* ]] && COMPREPLY=( $(compgen -W "${ssh_hosts}" -- ${cur}) )
}
complete -o bashdefault -o default -o nospace -F _ssh_hosts ssh 2>/dev/null \
|| complete -o default -o nospace -F _ssh_hosts ssh
complete -o bashdefault -o default -o nospace -F _ssh_hosts scp 2>/dev/null \
|| complete -o default -o nospace -F _ssh_hosts scp
Sweet. All that you have to do now is:
$ ssh TAB TAB
host1 host2 host3
We are a bit more efficient today.
Cloud computing and being lazy
The need to create template images in our cloud environment is obvious. Especially with Amazon EC2 offering an amazing API and spot instances in ridiculously low prices.
In the following post I’ll show what I am doing in order to prepare a “puppet-ready” image.
Puppet for the rescue
In my environment I have puppet configured and provisioning any of my machines. With puppet I can deploy anything I need – “if it’s not in puppet – it doesn’t exist”.
Coupled with Puppet dashboard the interface is rather simple for manually adding nodes. But doing stuff manually is slow. I assume that given the right base image I (and you) can deploy and configure that machine with puppet.
In other words, the ability to convert a bare machine to a usable machine is taken for granted (although it is heaps of work on its own).
Handling the “bare” image
Most cloud computing providers today provide you (usually) with an interface for starting/stopping/provisioning machines on its cloud.
The images the cloud providers are usually supplying are bare, such as CentOS 6.3 with nothing. Configuring an image like that will require some manual labour as you can’t even auto-login to it without some random password or something similar.
Create a “puppet ready” image
So if I boot up a simple CentOS 6.x image, these are the steps I’m taking in order to configure it to be “puppet ready” (and I’ll do it only once per cloud computing provider):
# install EPEL, because it's really useful
rpm -q epel-release-6-8 || rpm -Uvh http://download.fedoraproject.org/pub/epel/6/`uname -i`/epel-release-6-8.noarch.rpm
# install puppet labs repository
rpm -q puppetlabs-release-6-6 || rpm -ivh http://yum.puppetlabs.com/el/6/products/i386/puppetlabs-release-6-6.noarch.rpm
# i usually disable selinux, because it's mostly a pain
setenforce 0
sed -i -e 's!^SELINUX=.*!SELINUX=disabled!' /etc/selinux/config
# install puppet
yum -y install puppet
# basic puppet configuration
echo '[agent]' > /etc/puppet/puppet.conf
echo ' pluginsync = true' >> /etc/puppet/puppet.conf
echo ' report = true' >> /etc/puppet/puppet.conf
echo ' server = YOUR_PUPPETMASTER_ADDRESS' >> /etc/puppet/puppet.conf
echo ' rundir = /var/run/puppet' >> /etc/puppet/puppet.conf
# run an update
yum update -y
# highly recommended is to install any package you might deploy later on
# the reason behind it is that it will save a lot of precious time if you
# install 'httpd' just once, instead of 300 times, if you deploy 300 machines
# also recommended is to run any 'baseline' configuration you have for your nodes here
# such as changing SSH port or applying common firewall configuration for instance
yum install -y MANY_PACKAGES_YOU_MIGHT_USE
# and now comes the cleanup phase, where we actually make the machine "bare", removing
# any identity it could have
# set machine hostname to 'changeme'
hostname changeme
sed -i -e "s/^HOSTNAME=.*/HOSTNAME=changeme" /etc/sysconfig/network
# remove puppet generated certificates (they should be recreated)
rm -rf /etc/puppet/ssl
# stop puppet, as you should change the hostname before it will be permitted to run again
service puppet stop; chkconfig puppet off
# remove SSH keys - they should be recreated with the new machine identity
rm -f /etc/ssh/ssh_host_*
# finally add your key to authorized_keys
mkdir -p /root/.ssh; echo "YOUR_SSH_PUBLIC_KEY" > /root/.ssh/authorized_keys
Power off the machine and create an image. This is your “puppet-ready” image.
Using the image
Now you’re good to go, create a new image from that machine and any machine you’re going to create in the future should be based on that image.
When creating a new machine the steps you should follow are:
- Start the machine with the “puppet-ready” image
- Set the machine’s hostname
hostname=uga.bait.com
hostname $hostname
sed -i -e "s/^HOSTNAME=.*/HOSTNAME=$hostname/" /etc/sysconfig/network
Run ‘puppet agent –test’ to generate a new certificate request
Add the puppet configuration for the machine, for puppet dashboard it’ll be something similar to:
hostname=uga.bait.com
sudo -u puppet-dashboard RAILS_ENV=production rake -f /usr/share/puppet-dashboard/Rakefile node:add name=$hostname
sudo -u puppet-dashboard RAILS_ENV=production rake -f /usr/share/puppet-dashboard/Rakefile node:groups name=$hostname groups=group1,group2
sudo -u puppet-dashboard RAILS_ENV=production rake -f /usr/share/puppet-dashboard/Rakefile node:parameters name=$hostname parameters=parameter1=value1,parameter2=value2
Authorize the machine in puppetmaster (if autosign is disabled)
Run puppet:
# initial run, might actually change stuff
puppet agent --test
service puppet start; chkconfig puppet on
This is 90% of the work if you want to quickly create usable machines on the fly, it shortens the process significantly and can be easily implemented to support virtually any cloud computing provider!
I personally have it all scripted and a new instance on EC2 takes me 2-3 minutes to load + configure. It even notifies me politely via email when it’s done.
I’m such a lazy bastard.
Continued from my previous article at:
https://bashinglinux.wordpress.com/2013/02/18/bumblebee-and-fc18-a-horror-show/
This is a little manual about running primus with the previous setup I’ve suggested.
Packages
Pretty simple:
yum install glibc-devel.x86_64 glibc-devel.i686 libX11-devel.x86_64 libX11-devel.i686
We should be good to go in terms of packages (both x86_64 and i686)
Download and compile primus
Clone from github:
cd /tmp && git clone https://github.com/amonakov/primus.git
Compiling for x86_64:
export PRIMUS_libGLd='/usr/lib64/libGL.so.1'
export PRIMUS_libGLa='/usr/lib64/nvidia/libGL.so.1'
LIBDIR=lib64 make
unset PRIMUS_libGLd PRIMUS_libGLa
And for i686 (32 bit):
export PRIMUS_libGLd='/usr/lib/libGL.so.1'
export PRIMUS_libGLa='/usr/lib/nvidia/libGL.so.1'
CXX=g++\ -m32 LIBDIR=lib make
unset PRIMUS_libGLd PRIMUS_libGLa
Running
Running with x86_64:
cd /tmp/primus && \
LD_LIBRARY_PATH=/usr/lib64/nvidia:lib64 ./primusrun glxspheres
Untested by me, but that should be the procedure for i686 (32 bit):
cd /tmp/primus && \
LD_LIBRARY_PATH=/usr/lib/nvidia:lib ./primusrun YOUR_32_BIT_OPENGL_APP
Preface
I’ve seen numerous posts about how to get bumlebee, optirun and nvidia to run on Fedora Core 18, the only problem was that all of them were using the open source (and somewhat slow) nouveau driver.
I wanted to use the official Nvidia binary driver which is heaps faster.
My configuration is a Lenovo T430s with a NVS 5200M.
Following is a tick list of things to do to get it running (at least on my configuration with FC18 x86_64).
Installing the Nvidia driver
The purpose of this paragraph is to show you how to install the Nvidia driver without overwriting your current OpenGL libraries. Simply download the installer and run:
yum install libbsd-devel dkms
./NVIDIA-Linux-x86_64-XXX.XX.run --x-module-path=/usr/lib64/xorg/nvidia --opengl-libdir=lib64/nvidia --compat32-libdir=lib/nvidia --utility-libdir=lib64/nvidia --no-x-check --disable-nouveau --no-recursion
Even though we ask it to disable nouveau, it still wouldn’t.
This method will not ruin all the good stuff in /usr/lib and /usr/lib64.
Disabling nouveau
Disabling nouveau is rather simple, we need to blacklist it and remove it from initrd:
echo "blacklist nouveau" > /etc/modprobe.d/nvidia.conf
dracut /boot/initramfs-$(uname -r).img $(uname -r) --omit-drivers nouveau
Good on us. You may either reboot now to verify that nouveau is out of the house, or manually rmmod it:
rmmod nouveau
Bumblebee and all the rest
Install VirtualGL:
yum --enablerepo=updates-testing install VirtualGL
Remove some rubbish xorg files:
rm -f /etc/X11/xorg.conf
Download bbswtich and install with dkms:
cd /tmp && wget https://github.com/downloads/Bumblebee-Project/bbswitch/bbswitch-0.5.tar.gz
tar -xf bbswitch-0.5.tar.gz
cp -av bbswitch-0.5 /usr/src
ln -s /usr/src/bbswitch-0.5/dkms/dkms.conf /usr/src/bbswitch-0.5/dkms.conf
dkms add -m bbswitch -v 0.5
dkms build -m bbswitch -v 0.5
dkms install -m bbswitch -v 0.5
Download bumblebee and install:
cd /tmp && wget https://github.com/downloads/Bumblebee-Project/Bumblebee/bumblebee-3.0.1.tar.gz
tar -xf bumblebee-3.0.1.tar.gz
cd bumblebee-3.0.1
./configure --prefix=/usr --sysconfdir=/etc
make && make install
cp scripts/systemd/bumblebeed.service /lib/systemd/system/
sed -i -e 's#ExecStart=.*#ExecStart=/usr/sbin/bumblebeed --config /etc/bumblebee/bumblebee.conf#g' /lib/systemd/system/bumblebeed.service
chkconfig bumblebeed on
Bumblebee configuration is at /etc/bumblebee/bumblebee.conf, edit it to have this:
[bumblebeed]
VirtualDisplay=:8
KeepUnusedXServer=false
ServerGroup=bumblebee
TurnCardOffAtExit=false
NoEcoModeOverride=false
Driver=nvidia
[optirun]
VGLTransport=proxy
AllowFallbackToIGC=false
[driver-nvidia]
KernelDriver=nvidia
Module=nvidia
PMMethod=bbswitch
LibraryPath=/usr/lib64/nvidia:/usr/lib/nvidia:/usr/lib64/xorg/nvidia
XorgModulePath=/usr/lib64/xorg/nvidia/extensions,/usr/lib64/xorg/nvidia/drivers,/usr/lib64/xorg/modules
XorgConfFile=/etc/bumblebee/xorg.conf.nvidia
The default /etc/bumblebee/xorg.conf.nvidia which comes with bumblebee is ok, but in case you want to make sure, here is mine:
Section "ServerLayout"
Identifier "Layout0"
Option "AutoAddDevices" "false"
EndSection
Section "Device"
Identifier "Device1"
Driver "nvidia"
VendorName "NVIDIA Corporation"
Option "NoLogo" "true"
Option "UseEDID" "false"
Option "ConnectedMonitor" "DFP"
EndSection
Add yourself to bumblebee group:
groupadd bumblebee
usermod -a -G bumblebee YOUR_USERNAME
Restart bumblebeed:
systemctl restart bumblebeed.service
Testing
To run with your onboard graphics card:
glxspheres
Running with nvidia discrete graphics:
optirun glxspheres
Useful links
Inspiration from:
http://duxyng.wordpress.com/2012/01/26/finally-working-nvidia-optimus-on-fedora/
Download links:
https://github.com/Bumblebee-Project/Bumblebee/downloads
https://github.com/Bumblebee-Project/bbswitch/downloads
http://www.nvidia.com/Download/index.aspx
If it works for you, please let me know!!
And if it doesn’t, perhaps I could help.
Have decided to publish the infamous Bash scripting conventions.
Here they are:
https://github.com/danfruehauf/Scripts/tree/master/bash_scripting_conventions
Please, comment, challenge and help me modify it. I’m very open for feedback.
Bashing Linux 