Building base images for Vagrant with a Makefile

I needed a base image “box” for my Puppet-Gluster+Vagrant work. It would have been great if good boxes already existed, and even better if it were easy to build my own. As it turns out, I wasn’t able to satisfy either of these conditions, so I’ve had to build one myself! I’ve published all of my code, so that you can use these techniques and tools too!

Status quo:

Having an NIH problem is bad for your vision, and it’s best to benefit from existing tools before creating your own. I first tried using vagrant-cachier, and then veewee, and packer. Vagrant-cachier is a great tool, but it turned out not being very useful because there weren’t any base images available for download that met my needs. Veewee and packer can build those images, but they both failed in doing so for different reasons. Hopefully this situation will improve in the future.

Writing a script:

I started by hacking together a short shell script of commands for building base images. There wasn’t much programming involved as the process was fairly linear, but it was useful to figure out what needed getting done.

I decided to use the excellent virt-builder command to put together the base image. This is exactly what it’s good at doing! To install it on Fedora 20, you can run:

$ sudo yum install libguestfs-tools

It wasn’t available in Fedora 19, but after a lot of pain, I managed to build (mostly correct?) packages. I have posted them online if you are brave (or crazy?) enough to want them.

Using the right tool:

After building a few images, I realized that a shell script was the wrong tool, and that it was time for an upgrade. What was the right tool? GNU Make! After working on this for more hours than I’m ready to admit, I present to you, a lovingly crafted virtual machine base image (“box”) builder:

Makefile

The Makefile itself is quite compact. It uses a few shell scripts to do some of the customization, and builds a clean image in about ten minutes. To use it, just run make.

Customization:

At the moment, it builds x86_64, CentOS 6.5+ machines for vagrant-libvirt, but you can edit the Makefile to build a custom image of your choosing. I’ve gone out of my way to add an $(OUTPUT) variable to the Makefile so that your generated files get saved in /tmp/ or somewhere outside of your source tree.

Download the image:

If you’d like to download the image that I generated, it is being generously hosted by the Gluster community here. If you’re using the Vagrantfile from my Puppet-Gluster+Vagrant setup, then you don’t have to download it manually, this will happen automatically.

Open issues:

The biggest issue with the images is that SELinux gets disabled! You might be okay with this, but it’s actually quite unfortunate. It is disabled to avoid the SELinux relabelling that happens on first boot, as this overhead defeats the usefulness of a fast vagrant deployment. If you know of a way to fix this problem, please let me know!

Example output:

If you’d like to see this in action, but don’t want to run it yourself, here’s an example run:

$ date && time make && date
Mon Jan 20 10:57:35 EST 2014
Running templater...
Running virt-builder...
[   1.0] Downloading: http://libguestfs.org/download/builder/centos-6.xz
[   4.0] Planning how to build this image
[   4.0] Uncompressing
[  19.0] Resizing (using virt-resize) to expand the disk to 40.0G
[ 173.0] Opening the new disk
[ 181.0] Setting a random seed
[ 181.0] Setting root password
[ 181.0] Installing packages: screen vim-enhanced git wget file man tree nmap tcpdump htop lsof telnet mlocate bind-utils koan iftop yum-utils nc rsync nfs-utils sudo openssh-server openssh-clients
[ 212.0] Uploading: files/epel-release-6-8.noarch.rpm to /root/epel-release-6-8.noarch.rpm
[ 212.0] Uploading: files/puppetlabs-release-el-6.noarch.rpm to /root/puppetlabs-release-el-6.noarch.rpm
[ 212.0] Uploading: files/selinux to /etc/selinux/config
[ 212.0] Deleting: /.autorelabel
[ 212.0] Running: yum install -y /root/epel-release-6-8.noarch.rpm && rm -f /root/epel-release-6-8.noarch.rpm
[ 214.0] Running: yum install -y bash-completion moreutils
[ 235.0] Running: yum install -y /root/puppetlabs-release-el-6.noarch.rpm && rm -f /root/puppetlabs-release-el-6.noarch.rpm
[ 239.0] Running: yum install -y puppet
[ 254.0] Running: yum update -y
[ 375.0] Running: files/user.sh
[ 376.0] Running: files/ssh.sh
[ 376.0] Running: files/network.sh
[ 376.0] Running: files/cleanup.sh
[ 377.0] Finishing off
Output: /home/james/tmp/builder/gluster/builder.img
Output size: 40.0G
Output format: qcow2
Total usable space: 38.2G
Free space: 37.3G (97%)
Running convert...
Running tar...
./Vagrantfile
./metadata.json
./box.img

real	9m10.523s
user	2m23.282s
sys	0m37.109s
Mon Jan 20 11:06:46 EST 2014
$

If you have any other questions, please let me know!

Happy hacking,

James

PS: Be careful when writing Makefile‘s. They can be dangerous if used improperly, and in fact I once took out part of my lib/ directory by running one. Woops!

UPDATE: This technique now exists in it’s own repo here: https://github.com/purpleidea/vagrant-builder

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Forcing firefox to remember passwords

There are a handful of websites out there that decide that they know better than your browser and tell it to not offer to save passwords. They do this by setting a form autocomplete attribute to off.

Since we already agree that HTML and the web are a terrible idea, hopefully we can find a way to hack around this. It turns out that I didn’t have to, because many others have solved this hack before me. The cleanest version I found is here: http://www.howtogeek.com/62980/how-to-force-your-browser-to-remember-passwords/

It’s not that complicated actually, a little bookmarklet (javascript code, stored in a bookmark, and activated when you open it) is saved in your browser, and on activation, it loops through all the page’s forms and turns on the autocomplete off‘s.

I’ve copied the code here, in the interests of archiving this very useful hack. Here you go:

Shortened form:

javascript:(function(){var%20ac,c,f,fa,fe,fea,x,y,z;ac="autocomplete";c=0;f=document.forms;for(x=0;x<f.length;x++){fa=f[x].attributes;for(y=0;y<fa.length;y++){if(fa[y].name.toLowerCase()==ac){fa[y].value="on";c++;}}fe=f[x].elements;for(y=0;y<fe.length;y++){fea=fe[y].attributes;for(z=0;z<fea.length;z++){if(fea[z].name.toLowerCase()==ac){fea[z].value="on";c++;}}}}alert("Enabled%20'"+ac+"'%20on%20"+c+"%20objects.");})();

Long form:

function() {
   var ac, c, f, fa, fe, fea, x, y, z;
   //ac = autocomplete constant (attribute to search for)
   //c = count of the number of times the autocomplete constant was found
   //f = all forms on the current page
   //fa = attibutes in the current form
   //fe = elements in the current form
   //fea = attibutes in the current form element
   //x,y,z = loop variables

   ac = "autocomplete";
   c = 0;
   f = document.forms;

   //cycle through each form
   for(x = 0; x < f.length; x++) {
      fa = f[x].attributes;
      //cycle through each attribute in the form
      for(y = 0; y < fa.length; y++) {
         //check for autocomplete in the form attribute
         if(fa[y].name.toLowerCase() == ac) {
            fa[y].value = "on";
            c++;
         }
      }

      fe = f[x].elements;
      //cycle through each element in the form
      for(y = 0; y < fe.length; y++) {
         fea = fe[y].attributes;
         //cycle through each attribute in the element
         for(z = 0; z < fea.length; z++) {
            //check for autocomplete in the element attribute
            if(fea[z].name.toLowerCase() == ac) {
               fea[z].value = "on";
               c++;
            }
         }
      }
   }

   alert("Enabled '" + ac + "' on " + c + " objects.");
}

Happy hacking,

James

PS: Best friends forever if you can get firefox to natively integrate with the gnome-keyring. No I don’t want to force it to myself, get this code merged upstream please!

scary cool bash scripting inside a Makefile

Makefiles are both scary and wonderful. When both these adjectives are involved, it often makes for interesting hacking. This is likely the reason I use bash.

In any case, I digress, back to real work. I use Makefiles as a general purpose tool to launch any of a number of shell scripts which I use to maintain my code, and instead of actually having external shell scripts, I just build any necessary bash right into the Makefile.

One benefit of all this is that when you type “Make <target>”, the <target> can actually autocomplete which makes your shell experience that much more friendly.

In any case, let me show you the code in question. Please note the double $$ for shell execution and for variable referencing. The calls to rsync and sort make me pleased.

rsync -avz --include=*$(EXT) --exclude='*' --delete dist/ $(WWW)
# empty the file
echo -n '' > $(METADATA)
cd $(WWW);
for i in *$(EXT); do
b=$$(basename $$i $(EXT));
V=$$(echo -n $$(basename "`echo -n "$$b" | rev`"
"`echo -n "$(NAME)-" | rev`") | rev);
echo $(NAME) $$V $$i >> $(METADATA);
done;
sort -V -k 2 -o $(METADATA) $(METADATA) # sort by version key

The full Makefile can be found inside of the bash-tutor tarball.

scary man pages

while doing a little reading and research,  i ended up reading a bit of the hdparm man page. never in my life have i read such a scary man page. i guess it is appropriate for halloween, but it came 2 days late in my case. as a result of my being so impressed with the sheer amount of warnings in the manual, i have decided to compile them here.

–dco-restore
Reset all drive settings, features, and accessible capacities back to factory defaults and full capabilities. This command will fail if DCO is frozen/locked, or if a -Np maximum size restriction has also been set. This is EXTREMELY DANGEROUS and will very likely cause massive loss of data. DO NOT USE THIS COMMAND.

–drq-hsm-error
VERY DANGEROUS, DON’T EVEN THINK ABOUT USING IT. This flag causes hdparm to issue an IDENTIFY command to the kernel, but incorrectly marked as a “non-data” command. This results in the drive being left with its DataReQust(DRQ) line “stuck” high. This confuses the kernel drivers, and may crash the system immediately with massive data loss. The option exists to help in testing and fortifying the kernel against similar real-world drive malfunctions. VERY DANGEROUS, DO NOT USE!!

–fwdownload
When used, this should be the only flag given. It requires a file path immediately after the flag, indicating where the new drive firmware should be read from. The contents of this file will be sent to the drive using the (S)ATA DOWNLOAD MICROCODE command, using either transfer protocol 7 (entire file at once), or, if the drive supports it, transfer protocol 3 (segmented download). This command is EXTREMELY DANGEROUS and HAS NEVER BEEN PROVEN TO WORK and will probably destroy both the drive and all data on it. DO NOT USE THIS COMMAND.

-m
Get/set sector count for multiple sector I/O on the drive. A setting of 0 disables this feature. Multiple sector mode (aka IDE Block Mode), is a feature of most modern IDE hard drives, permitting the transfer of multiple sectors per I/O interrupt, rather than the usual one sector per interrupt. When this feature is enabled, it typically reduces operating system overhead for disk I/O by 30-50%. On many systems, it also provides increased data throughput of anywhere from 5% to 50%. Some drives, however (most notably the WD Caviar series), seem to run slower with multiple mode enabled. Your mileage may vary. Most drives support the minimum settings of 2, 4, 8, or 16 (sectors). Larger settings may also be possible, depending on the drive. A setting of 16 or 32 seems optimal on many systems. Western Digital recommends lower settings of 4 to 8 on many of their drives, due tiny (32kB) drive buffers and non-optimized buffering algorithms. The -i flag can be used to find the maximum setting supported by an installed drive (look for MaxMultSect in the output). Some drives claim to support multiple mode, but lose data at some settings. Under rare circumstances, such failures can result in massive filesystem corruption.

-R
Register an IDE interface (DANGEROUS). See the -U option for more information.

-u
Get/set interrupt-unmask flag for the drive. A setting of 1 permits the driver to unmask other interrupts during processing of a disk interrupt, which greatly improves Linux´s responsiveness and eliminates “serial port overrun” errors. Use this feature with caution: some drive/controller combinations do not tolerate the increased I/O latencies possible when this feature is enabled, resulting in massive filesystem corruption. In particular, CMD-640B and RZ1000 (E)IDE interfaces can be unreliable (due to a hardware flaw) when this option is used with kernel versions earlier than 2.0.13. Disabling the IDE prefetch feature of these interfaces (usually a BIOS/CMOS setting) provides a safe fix for the problem for use with earlier kernels.

-U
Un-register an IDE interface (DANGEROUS). The companion for the -R option. Intended for use with hardware made specifically for hot-swapping (very rare!). Use with knowledge and extreme caution as this can easily hang or damage your system. The hdparm source distribution includes a ´contrib´ directory with some user-donated scripts for hot-swapping on the UltraBay of a ThinkPad 600E. Use at your own risk.

-w
Perform a device reset (DANGEROUS). Do NOT use this option. It exists for unlikely situations where a reboot might otherwise be required to get a confused drive back into a useable state.

-x
Tristate device for hotswap (DANGEROUS).

–security-unlock PWD
–security-set-pass PWD
–security-disable PWD
–security-erase PWD
–security-erase-enhanced PWD
–user-master USER
–security-mode MODE
[…]
THIS FEATURE IS EXPERIMENTAL AND NOT WELL TESTED. USE AT YOUR OWN RISK.

i think it is now safe to say that:

# rm -rf /

has now officially been replaced with the much more dangerous:

# hdparm -mRuUwx --dco-restore --drq-hsm-error --fwdownload --security-unlock PWD --security-set-pass PWD --security-disable PWD --security-erase PWD --security-erase-enhanced PWD --user-master USER --security-mode MODE [device]

have fun kiddies!