Is there any tool (GUI or online) for developing and debugging apache’s mod_rewrite (Rewrite Engine) rules?
Something like Regex tools that get input (for example URLs per line) and some rewrite rules; Then displays rules’s output.

you can use rewrite log file for debugging :

<IfModule mod_rewrite.c>
    RewriteLog "/home/test/public/logs/rewrite.log"
    RewriteLogLevel 3
</IfModule>

OR you can follow this detailed debugging tutorial:

http://www.askapache.com/htaccess/crazy-advanced-mod_rewrite-tutorial.html

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I have some embedded boards running American Megatrends bios with embedded linux as the OS. The problem I have is that the industrial flash ide’s will be corrupted on power loss. I have them formatted as ext4. Whenever this happens, I can usually fix the flash with fsck, but this will not be possible in our deployments. I have heard that disabling the write-caching should help, but I can’t figure out how to do it. Also, is there any thing else I should do?

More Info

The drive is a 4gb ide flash module.
I have one partition which is ext4. The O.S. is installed on that partition and grub is my bootloader.

fdisk -l shows /dev/sda as my flash module with /dev/sda1 as my primary partition.

After a power loss I usually cannot make it entirely through the boot init scripts.

When I mount the drive on another P.C. I run fsck /dev/sda1. It always shows messages like

"zero datetime on node 1553 ... fix (y)?"

I fix them and it boots fine until the next power loss.

When I get to the office tomorrow, I will post the actual output of fdisk -l

This is all I know about how the system works. I am not a systems guy, I am a Software Engineer that has a habit of getting into predicaments that are outside of his job description. I know how to format drives, install a bootloader, write software, and hack on an operating system.

Here is the output from dumpe2fs

#sudo dumpe2fs /dev/sda1
dumpe2fs 1.41.12 (17-May-2010)
Filesystem volume name:   VideoServer
Last mounted on:          /
Filesystem UUID:          9cba62b0-8038-4913-be30-8eb211b23d78
Filesystem magic number:  0xEF53
Filesystem revision #:    1 (dynamic)
Filesystem features:      ext_attr resize_inode dir_index filetype extent flex_bg sparse_super large_file huge_file uninit_bg dir_nlink extra_isize
Filesystem flags:         signed_directory_hash 
Default mount options:    (none)
Filesystem state:         not clean
Errors behavior:          Continue
Filesystem OS type:       Linux
Inode count:              245760
Block count:              977949
Reserved block count:     48896
Free blocks:              158584
Free inodes:              102920
First block:              0
Block size:               4096
Fragment size:            4096
Reserved GDT blocks:      239
Blocks per group:         32768
Fragments per group:      32768
Inodes per group:         8192
Inode blocks per group:   512
Flex block group size:    16
Filesystem created:       Fri Feb  4 15:12:00 2011
Last mount time:          Sun Oct  2 23:48:37 2011
Last write time:          Mon Oct  3 16:34:01 2011
Mount count:              2
Maximum mount count:      26
Last checked:             Tue Oct  4 07:44:50 2011
Check interval:           15552000 (6 months)
Next check after:         Sun Apr  1 07:44:50 2012
Lifetime writes:          21 GB
Reserved blocks uid:      0 (user root)
Reserved blocks gid:      0 (group root)
First inode:              11
Inode size:           256
Required extra isize:     28
Desired extra isize:      28
Default directory hash:   half_md4
Directory Hash Seed:      249d2b79-1e20-49a3-b324-6cb631294a63
Journal backup:           inode blocks

The write cache has usually nothing to do with the BIOS, mostly there is no option for switching disk cache settings in there. With linux, using hdparm -W 0 should help.

The setting is persistent, so if you don’t have hdparm to play around with in your production systems, you should be able to disable the disk write cache on a different system and replug the disk.

BTW: I’d second the idea of a non-writable root filesystem (so your system could boot in a kind of “recovery mode” and allow for remote access even if the writable filesystem is not mountable for some reason). And if you can change the hardware design, consider using mtd devices instead of IDE/SATA disks with a flash-aware filesystem like jffs2. We’ve been using this combination with several embedded devices (mostly VPN router solutions in the field) for several years with good results.

Update: the root of your problem seems to be that you are running an ext4 filesystem with journaling disabled – has_journal is missing from the Filesystem features list. Just shut down all services, check if anything still has open files using lsof +f -- /, remount your root partition read-only with mount -o remount,ro /, enable the journal with tune2fs -O has_journal /dev/sda1 and set up the “ordered” journal mode as the default mount option using tune2fs -o journal_data_ordered /dev/sda1 – you will have to re-run fsck (preferably from a rescue system) and remount root / reboot after this operation.

With these settings in place, the metadata is guaranteed to be recoverable from the journal even in the event of a sudden power failure. The actual data is also consistently written to disk, although you may see data of several seconds before the power outage lost on bootup. If this is not acceptable, you might consider using the tune2fs -o journal_data /dev/sda1 mount option with your filesystem – this would include all data written to disk in the journal – this obviously would give you better data consistency but at the cost of a performance penalty and a higher wear level on your SSD.

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What do you use for temporarily externally mounting 3.5″ SATA and IDE hard drives? When I’m in the field and just have a laptop with me, I’d like to be able to mount a client’s drive to my laptop for data recovery, etc. Is a separate USB enclosure for SATA and IDE the best option? Any other ideas?

I use the Newer Technology USB 2.0 Universal Drive Adapter. It’s inexpensive, small, and works on IDE or SATA drives.

http://eshop.macsales.com/item/Newer%20Technology/U2NV2SPATA/

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I have an old 160 GB EIDE ATA-133 hard drive, which I would like to use in my Dell PowerEdge T105 server.

However, the cables inside the T105 are SATA, which won’t connect to the drive.

Is there some way I can connect this? Are there adapter cables available? Or do I need to buy some additional hardware for the server to use this drive?

You can find PCI PATA adapters for reasonable prices, usually cheaper than a SATA-to-PATA adapter.

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I have a Linux server (CentOS 5.5) that has two identical IDE hard drives. I’ve used software RAID (mdadm) to create mirrors for each filesystem, so that either hard drive could fail and no data would be lost.

Today one of my hard drives failed. The whole point of RAID should be to allow the system to keep running when this happens; but what happened instead was that the console began spewing the same 4 lines over and over:

hdb: task_out_intr: status=0x61 { DriveReady DeviceFault Error }
hdb: task_out_intr: error=0x04 { DriveStatusError }
ide: failed opcode was: unknown
ide0: reset: success

Due to the high rate of errors being produced, the console was unusable. I was able to SSH in, but the first command I tried just hung. I SSH’ed in again and tried to reboot, but that got hung up as well. Ultimately I had to physically reset the machine.

I know how to remove the failed drive from the MD and replace it, etc. But having the machine lock up and become unusable in this situation seems to defeat the whole point of having RAID mirrors in the first place.

Is this just the way the Linux kernel always behaves in this situation? Or is there some way to configure the kernel so that when a hard drive fails, it rate-limits the errors being produced, and doesn’t prevent the machine from being used and cleanly rebooted?

I haven’t run into this, but since you’re using software RAID, it’s possible that the hard disk failure is causing something to interfere with I/O on the disk controller, so you’re getting other failures like the locking up of commands.

The data should be intact (unless it’s corrupted, in which case you have duplicated corruption). If the drive itself failed you should be able to power down, remove the bad drive, power back up and hopefully things will come back online with a broken mirror set.

Sounds to me like the nature of the failure isn’t sitting well with the controller. Take out the bad drive. It doesn’t do you any good to keep it in there and can be causing more harm.

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