11 Jun

How to Repair a Server Stuck at the Grub Prompt

bin-bash

I recently had an issue with a server hosted at OVH.com.   One Saturday, it completely failed to boot and there was no SSH access.  After a little pleading with OVH to fix the server(since I had no access) , I was flatly told “No” several times. This was a dedicated server and as such, I was responsible for all aspects of its software.  “But your physical disks are failing to mount!” No help.  Grrr, ok I can solve this.

Here’s the only problem, I don’t even know what the error is on boot! I can’t see any of the boot screen, so I don’t know where its failing.

OVH has a convenient feature know as Rescue Mode which allows you to boot to an alternative  OS, so you can mount and correct any issues on the primary drive.  Utilizing this feature I got access to the disks and RAID array.  Everything seemed fine, but I ran through all the checks to be sure.

  • Hard Disks – No errors
  • Raid Array – Needed to be resynced, but does not fix boot
  • FileSystem – OK
  • Boot Logs – No help
  • Partitions – Disks are out of order, but does not fix boot

At this point, I’m out of ideas, so I call OVH one more time and ask them to look at the boot screen and tell me where its stuck.  They agree and tell me it boots to GRUB> prompt and stops.  Ok, this is good information.

I log back into rescue and scour the internet for a way to fix this.  The answer is found in an obscure ubuntu forum, which perfectly describes a way to reset the grub loader on each disk in the array, when utilizing a rescue mode.

$ sudo fdisk -l (From this you need to find the device name of your physical drive that won't boot, something like “/dev/sdxy″ - where x is the drive and y is the root partition. Since I was using a software RAID, root (/) was on md1)
$ sudo mount /dev/sdxy /mnt (Mount the root partition)
$ sudo mount --bind /dev /mnt/dev
$ sudo mount --bind /proc /mnt/proc
$ sudo mount --bind /sys /mnt/sys
$ sudo chroot /mnt  (This will change the root of executables to your your drive that won't boot)
$ grub-mkconfig -o /boot/grub/grub.cfg (insure that there are NO error messages)
$ grub-install /dev/sdx (NOTE that this is the drive and not the partition. try grub-install --recheck /dev/sdxy if it fails)
Ctrl+D (to exit out of chroot)
$ sudo umount /mnt/dev
$ sudo umount /mnt/proc
$ sudo umount /mnt/sys
$ sudo umount /mnt

Reboot!

Hopefully this will save someone some agony in the future and give you a few hours of your life back.

29 Mar

Move Forward or Be Left Standing Still

He who embraces his fears and moves in any direction, will learn from his mistakes and move forward. He who simply acknowledges his fears, will never succeed or fail. Rather he will be left standing still, straining in vain for peace.

– Tony C

08 Nov

A Check-in On Priorities

The Dalai Lama, when asked what surprised him most about humanity, answered:

“Man…. Because he sacrifices his health in order to make money.

Then he sacrifices money to recuperate his health.

And then he is so anxious about the future that he does not enjoy the present.

The result being that he does not live in the present or the future;  he lives as if he is never going to die, and then dies having never really lived.”

15 Oct

Apple Quietly Updates Website in Response to Watch Scratch Issues

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I had been wearing a demo Apple Watch Sport for a few days, when I noticed a few scratches on the screen. Damn, I thought. It had only been a few days and I hadn’t bumped or scraped it on anything significant. In addition, I had been cleaning it with a microfiber cloth, so I was sure it hadn’t been from that. But it was still odd considering how long I’ve had an iPhone 6 with no cover and 0 scratches. So I did a little digging.

Sure enough there are a few threads on Apple’s own website detailing how common, everyday usage is resulting in scratches. Disappointing, but maybe people are simply being careless. However, for some non-transparent reason Apple has also quietly updated their product text removing all mention of being scratch resistant. 

Rolling back 2 weeks on Apple’s own product page for the watch, we see the following text. Notice the phrase, “especially resistant to scratches and impact.

Screen Shot 2015-09-27 at 6.41.28 AM

But if you look at the current version of the product page, you’ll see this text.

Screen Shot 2015-09-27 at 6.39.12 AM

Apple removed front page, product messaging referencing its watch being scratch proof.

07 May

Caching Proxy Requests and Stripping Params with Nginx

nginx

I recently need to set up caching for a very slow API service I was working with.  However the app I was working with forced a query param of “timestamp” on all requests.  This effectively killed the cache because all api requests were flowing through a single endpoint, and only the query params differentiated the requests.  So here’s how to set up caching and strip out query params with nginx.

http {
    # Create a storage location for 
    # caching and call this location "my-app"
    proxy_cache_path /data/nginx/cache levels=1:2 
         keys_zone=global:10m 
         max_size=100m inactive=60m;
    
    server {
    
        location /api/  {
            # Strip out query param "timestamp"
            if ($args ~ (.*)&timestamp=[^&]*(.*)) {
                set $args $1$2;
            }

            # Use the "my-app" cache defined above
            proxy_cache my-app;

            # Only cache 200 responses and cache for 20mins
            proxy_cache_valid 200 20m;

            # Create a unique cache key
            proxy_cache_key 
                "$scheme$request_method$host$uri$is_args$args";
            
            # Proxy the request
            proxy_pass http://myapi.com;
        }
}
18 Apr

Fiber Optic Star Ceiling Panel with Day Time Stars

Originally posed to Instructables

Picture of Fiber Optic Star Ceiling Panel with Day Time Stars

I wanted to create a star ceiling, but since we are currently renting, I didn’t want to drill into the actual ceiling. So here’s how to create a portable star ceiling you can take with you. The total cost of this project is around USD $100

Step 1: Purchase fiber optic driver and cable

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I purchased this 150 light set off of ebay for around $60. This one came with a remote control and 16 colors to choose from. In addition, it’s low profile driver will be perfect to fit in the frame.

Step 2: Purchase a poster board

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I wanted something that was going to be sturdy enough to drill holes through, hold all the cables behind it, and look stylish. I came across this at Target for around $25.

Step 3: Remove the cardboard poster backing

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I removed the plastic cover from the poster to leave just the cardboard frame.

Step 4: Paint it black

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Next I grabbed some MATTE black spray paint and gave a good solid coating over the back of the poster board

Step 5: (Optional) Day time stars

Picture of (Optional) Day time stars

I didn’t want my star ceiling to look like a solid black tile during the daytime, so using some white GLOSS spray paint I added some daytime stars. To do this, simply press down very gently on the top nozzle of the spray paint, till it sputters. It should look like it spitting. Then quickly aim it at your black background. It should only take a few spits to create the desired look

Step 6: Place the backboard in the frame

Picture of Place the backboard in the frame

Step 7: Drill holes for starfeild

Picture of Drill holes for starfeild

I highly recommend you drill holes where the daytime stars appear. This is because they will already have a very nice distribution across the entire surface of the board. I tried to make my own pattern instead and in looks very contrived instead of natural looking.

Step 8: Light shining through

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Make sure all of your holes are clean and you patch up any unsightly looking spots on the front.

Step 9: Set your fiber optic driver foundation

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Place your fiber optic driver in a place off to the side of the frame. Then secure with zip ties.

Step 10: Place fiber optic lights through pre-drilled holes

Picture of Place fiber optic lights through pre-drilled holes
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Grabbing groups of lights at a time, start running the cables through your holes. You’ll want to keep these group somewhat organized, so I used more zip-ties. The group simply helps you lay the cables flat as you prepare to mount to ceiling. Don’t worry about the cables peaking through the front, we’ll trim those back later.

Step 11: Glue it good

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Once you’ve got all of your cables placed in the holes, you can start gluing to keep them in place. I used Elmers Clear Glue liberally on every singly hole.

Step 12: Allow 12 hours for glue to dry

Picture of Allow 12 hours for glue to dry

Step 13: Trim back the ends

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After the glue has dried, you’ll have a lot of cables sticking through the front. I used fingernail clippers to trim these flush with the board.

Step 14: Mount it

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That’s pretty much it for building the star panel. Now you can mount the panel in way you light and enjoy your new star field!