Running CrashPlan on a headless CentOS/cpanel server

I was helping someone figure out how to back up their CentOS/Cpanel-based web server using CrashPlan.  He was already backing it up via rsync, but he wanted to back it up with a cloud backup product.  Code42 advertises that CrashPlan and CrashPlanPro support Linux, so how hard could it be?  Not hard at all if you know what to do.  But if you're on a headless web server you will be at the mercy of what you can find on the Internet, as Code42 won't help you at all as you're running an "unsupported configuration."

We got it to work, but only after trying multiple different methods that didn't work.  So I thought I'd describe what we did that eventually worked, and hopefully someone else will find this when they're in the same situation.

What didn't work

Code42 has an "unsupported" (but totally reliable) method to connect the CrashPlan app on your desktop to the CrashPlan service running on the web server by using ssh tunneling.  It's described here.  We were able to make that method work to configure the backup, but then the backup wouldn't run.  It just stayed stuck at "waiting for backup."  We contacted Code42, but they said they couldn't help us at all because we were running an unsupported configuration.  More on that at the end of this blog.

I thought the path to take would be to see if we could use the GUI that is supposed to display on the console of the server, but display it back to our desktop — a MacBook in this case.  (Something totally normally in Unix/Linux configurations.)  Then since I would be running the GUI directly from the server being backed up, I could then call support.  It turned out I ended up fixing it myself, though.  Let's see what I did.

Use ssh to forward X11

Since MacOS no longer uses the X11 Window System (BTW, it's not "X Windows"), I needed to install Xquartz, which I got from here. We followed the instructions and they seemed to work without a hitch.

X11 forwarding is not turned on by default in CentOS, so you have to edit the sshd config and restart sshd.  (Thanks to this blog post for helping me with this.)

sudo vi /etc/ssh/sshd_config

Uncomment and change these two lines to these values

X11Forwarding yes
X11UseLocalhost no

Now restart sshd.

$ sudo /etc/init.d/ssd reload

If you do not have xauth installed already, you need to install it, too.

$ sudo yum install xauth

Then back on the client where you want to see the GUI displayed, run this command:

$ ssh -l root -Y <linuxserver>

We saw a message that mentioned that xauth had created a new authority file.

To test if it was working correctly, we wanted to run xterm.  But that wasn't installed yet, so we installed it.

$ sudo yum install xterm
$ xterm

We waited a few second, and voila!  An xterm popped up on the Mac.  Awesome.  

Run CrashPlanDesktop

$ /usr/local/crashplan/bin/CrashPlanDesktop

It just returned the prompt to us and never did anything.  When we looked at the log directory, we saw error messages like the ones mentioned in this blog post.  We followed the suggestions in that blog post about creating temporary directories that CrashPlan can write to, and then specifying those directories in the run.conf file.

$ mkdir /root/.crashplan-tmp
$ mkdir /var/crashplan
$ vi /usr/local/crashplan/bin/run.conf

Add this to the end of the GUI_JAVA_OPTS line: ""
Add this to the end of the SRV_JAVA_OPTS line: ""

So run.conf now looks like this:

SRV_JAVA_OPTS="-Dfile.encoding=UTF-8 -Dapp=CrashPlanService -DappBaseName=CrashPlan -Xms20m -Xmx1024m -Dnetworkaddress.cache.ttl=300 -Dnetworkaddress.cache.negative.ttl=0 -Dc42.native.md5.enabled=false"

GUI_JAVA_OPTS="-Dfile.encoding=UTF-8 -Dapp=CrashPlanDesktop -DappBaseName=CrashPlan -Xms20m -Xmx512m -Dnetworkaddress.cache.ttl=300 -Dnetworkaddress.cache.negative.ttl=0 -Dc42.native.md5.enabled=false"

After that, everything worked perfectly!

Epilogue: Vindication

We fixed the GUI_JAVA_OPTS line first and were then able to run the GUI and configure the backups, but the backup was still stuck at "waiting for backup."  That was exactly what happened when we used the method of running the GUI local on the Mac and connecting to the CrashPlan service on the web server.  We then changed the SRV_JAVA_OPTS line and backups kicked off immediately.

In other words, the reason the backup wasn't working had nothing to do with us running an unsupported GUI configuration and had everything to do with the CrashPlan app trying to use directories that it couldn't write to.  Now back to Code42.

You can support something that isn't "supported"

Just because a customer is running an unsupported configuration, that doesn't mean you can't help him troubleshoot something.  The Code42 support person could have told us where the logs are, for example.  (Yes, they were in the obvious place of /usr/local/crashplan/logs, but we didn't know that.)  Luckily we googled the right thing and found that web page.  Luckily we knew what X11 was and could figure out how to install it on our Mac.  They could have at least helped a little.  Instead, they simply said I was running a system that didn't meet the minimum requirements, so he literally could not help me in any way to troubleshoot the problem.

This is very reminiscent of when I was trying to install a Drobo on my iMac in my house. The blog post I wrote back then was to tell Data Robotics to either support Linux or drop it.  I still feel the same way right now, but in this case the problem is not that they aren't supporting Linux; it's that they don't support headless Linux, which is what most web servers are running.

It isn't that hard to provide some "best effort" support to someone.  They could also enhance that "how to run CrashPlan on a headless Linux system" post by adding this X11 Forwarding idea to it.  Then if a customer has a few questions, help them.  Tell them it's unsupported and that the support will be best effort.  But make the effort.  Seriously.

----- Signature and Disclaimer -----

Written by W. Curtis Preston (@wcpreston). For those of you unfamiliar with my work, I've specialized in backup & recovery since 1993. I've written the O'Reilly books on backup and have worked with a number of native and commercial tools. I am now Chief Technical Evangelist at Druva, the leading provider of cloud-based data protection and data management tools for endpoints, infrastructure, and cloud applications. These posts reflect my own opinion and are not necessarily the opinion of my employer.

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