Category: Uncategorized

There are many tools that precompile PHP to make it run faster, up to now, my favorite is APC which also serves as a very fast value cache (for persistence between requests), a value cache much faster than memcached (but not as distributed).

For some time, i have been optimizing further by asking APC to never check if the file is modified on the disk, and whenever my software is modified i would manually clear the APC cache so that the whole script can be compiled all over again (I say compiled loosely speaking, in reality, it is simply turned into bytecode).

In any case, when you have a server with plenty of ram, it would be convenient if the PHP engine can read the file itself in byte and skip that step for compiled files, and from the way the linux kernel works, those files would be cached from disk into ram (because when a file is read or written, linux keeps a cache of it in ram).

So, bcompiler should be a good extension to PHP that fits such a criteria, and is probably my new way of running my scripts.

Also, bcompiler hides my source code, but i am not interested in that to protect my intellectual property, usually i am not very concerned about my intellectual property because it takes a very good programmer to understand a program and take things from it, and if the person is such a programmer, well, he can also write his own, and with the help of google, he can arrive at something like what i am doing, so to make a long story short, i am interested in hiding my source code for application security reasons, or Security through obscurity as MircoSfot would put it

I am writing this because the stuff you need is not in one place elsewhere, this is what you really need to know, and i want to keep this very short, if you like you can read more elsewhere, this one will only share what you really should know.

1- Do i need trim ?
For reading NO, so if you write once and read 102112913 times, you are good without trimming anything, without trimming, disk writes are slow, reading is absolutely not affected by trim.

2- What is the difference between the ext4 discard option and running fstrim myself manually every once in a while, or even put it in a cron job ?
on ext4 with trim enabled, blocks are trimmed (erased) whenever they are no longer in use by the file system, meaning, when data is deleted from a block, the physical flash memory is erased right after the data deletion, so your disk will remain trimmed all the time, the overhead is not much because the OS knows the block it just freed, so it simply does no more math other than issue a second command to trim, when you run fstrim, fstrim will read the whole file system, and whenever it finds an empty spot, it will trim (hardware erase).

3- i forgot to enable discard, do i just enable it and all is good, is that safe.
Yes it is safe, but enable it, then manually run fstrim only once, or you can wait, and eventually all spots will be trimmed after the get written to and erased again.

Ext4 (the new linux file system) supports TRIM when you mount the disk with the discard option, you can use tools to trim with ext2 or ext3, but it won’t be automatic and not as efficient.

1- But i want ext2 because i don’t want Journaling
ext2 is in fact ext3 without the journal, in ext4 you can remove the journal as well with no problems at all, there are no consequences, ext4 was designed to run with or without journaling

How do i format the disk in ext 4 and enable trim ?
For instructions on creating ext4 partitions, see here , as for the mounting, the line should have an extra option called discard and it should look something like this in your /etc/fstab

UUID=b7a491b1-a690-468f-882f-fbb4ac0a3b53       /hds/3tb            ext4     defaults,noatime,discard                0       1

You should be done, there is nothing more to do

3- I am stuck with ext2 and i don’t want to move, reformet and then move back again
before that, do you know that you can convert the drive to ext4 ?

4- I don’t want to convert anything to anything, i just want to manually trim
Thats easy, use the command
fstrim /hds/myssddisk

and you are done, but mind you, on anything but ext4, this will trim the whole unused space trimed or not trimmed

athurx is the atheros wireless driver, i have 2 atheros adapters on the same computer, one is 300Mb/s and the other is 150Mb/s

The reason for the blue screen is that the wireless interface driver(S) on my 64bit windows 7 (could be on any other platform too) is outdated, and it seems the old version of the driver has a problem in using 2 different atheros adapters on the same computer, the solution seems to lie in updating the drivers.

1- The Wireless N 150Mb/s (TP-LINK TL-WN722N, atheros AR9271 chip, should also apply to TL-WN721N that uses the same chip)
So, my atheros based TP-LINK TL-WN722N uses the Qualcomm atheros AR9271 chip, Windows installs driver version 2.0.0.32 dated 1/4/2010, and since Qualcomm atheros does not provide their drivers directly on there website, i downloaded the driver from TP-LINK, the new driver had version 2.0.0.62 and was dated more than a year later 4/20/2011, the problem with this driver is that it is NOT SIGNED, and therefore you have to manually install the driver then agree to install a non signed driver, simply asking windows to update from a directory will not update your driver, also check the driver versions before you update to see if your drivers have been updated.

2- The Wireless N 300Mb/s (tp-link TL-WN821N, Atheros AR7015)
This one also has an outdated driver that can be updated from the TP-LINK website, just like the one above.

Make sure you unplug the other driver as you update the software for the first, and once both have drivers installed, reboot and plug in both adapters, works like a dream up to now.

My web server got hacked today, i know because my datacenter contacted me today telling me that there is a bruit force attack originating from my server to another server on a different network, so what is happening is that my server got hacked, then the hacker is using the server she hacked to hack other servers by sending FTP requests.

So, how come i got hacked when i am so obsessed with security, well, in reality, this is just an intermediate machine that i used to run a certain script that would move my mail server, and i did not (and did not see the need) to secure it.

What i usually do to secure my server is simply install fail2ban, in this case i did not out of lazyness but here is how i got hacked and how fail2ban would have protected me.

Before i show you the log files, this whole problem would not happen if i had a strong password combined with fail2ban

In the complaining partie’s log files

Tue Jul 24 22:28:27 2012: user: hauvouuc service: ftp target: yyy.yyy.yyy.yyy source: xxx.xxx.xxx.xxx
Tue Jul 24 22:28:27 2012: user: pkmcndgq service: ftp target: yyy.yyy.yyy.yyy source: xxx.xxx.xxx.xxx
Tue Jul 24 22:28:27 2012: user: malumdvc1 service: ftp target: yyy.yyy.yyy.yyy source: xxx.xxx.xxx.xxx

In my log files (auth.log):

Many lines like the following right below each other

Jul 24 18:03:08 run sshd[14229]: pam_unix(sshd:auth): check pass; user unknown
Jul 24 18:03:08 run sshd[14229]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=9.12-14-84.ripe.coltfrance.com 
Jul 24 18:03:10 run sshd[14229]: Failed password for invalid user ts3 from 84.14.12.9 port 41014 ssh2
Jul 24 18:03:11 run sshd[14231]: Invalid user ts3 from 84.14.12.9

Anod some lines like this

Jul 25 15:30:46 run sshd[10728]: pam_unix(sshd:auth): check pass; user unknown
Jul 25 15:30:46 run sshd[10728]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=217.119.29.135 
Jul 25 15:30:48 run sshd[10728]: Failed password for invalid user public from 217.119.29.135 port 34292 ssh2
Jul 25 15:30:48 run sshd[10730]: Address 217.119.29.135 maps to gamma2-7.cust.smartspb.net, but this does not map back to the address - POSSIBLE BREAK-IN ATTEMPT!
Jul 25 15:30:48 run sshd[10730]: Invalid user public from 217.119.29.135

Thousands of lines like this one

Jul 24 14:12:38 run sshd[2025]: error: connect_to 213.186.33.207 port 80: failed.
Jul 24 14:12:39 run sshd[2025]: error: connect_to 192.168.10.24 port 2110: failed.
Jul 24 14:12:39 run sshd[2025]: error: connect_to 195.130.65.50 port 80: failed.

OR

Jul 24 06:41:19 run sshd[9824]: error: connect_to 213.186.33.207 port 80: failed.
Jul 24 06:41:19 run sshd[13434]: Failed password for invalid user test from 202.28.123.191 port 37830 ssh2
Jul 24 06:41:20 run sshd[9824]: error: connect_to 213.186.33.207 port 80: failed.

And more like this

Jul 24 08:19:18 run sshd[20882]: pam_unix(sshd:auth): check pass; user unknown
Jul 24 08:19:18 run sshd[20882]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=puck748.server4you.de 
Jul 24 08:19:21 run sshd[20882]: Failed password for invalid user kk from 85.25.235.73 port 49213 ssh2
Jul 24 08:19:21 run sshd[20884]: Invalid user css from 85.25.235.73

It is simple, here is what you need to know

You can format it EXT4, but ext2 and ext3 are also OK ! ext2 and ext3 allow up to 16TB disks, and file sizes of up to 2TB, ext4 allows much more.

Any linux kernel newer than 2.6.31 should work just fine with “Advanced format” drives using the exact same steps in this article.

MBR only supports 2TB drives, you need GPT, so let us get started

1- apt-get update
2- apt get install parted
3- parted /dev/sdc
4- mklabel gpt
5- Answer yes to: Warning: The existing disk label on /dev/sdb will be destroyed and all data on this disk will be lost. Do you want to continue?
Yes/No? yes
6- mkpart primary ext4 0% 100% (to make a partition as big as the disk (will occupy starting from first megabyte (for alignment) to the end of disk))
7- quit

FYI, if you want multiple partitions, here are the 2 lines that should replace step 6
6- mkpart primary ext4 0% 40%
6- mkpart primary ext4 40% 100%

and remember to format both (sdc1 and sdc2) when you are done with parted

Now to formatting the drive

mkfs.ext4 /dev/sdc1

Before mounting it, i like ext4, but i don’t want a journaling OS on this drive that is not the system drive, so i will need do a few things to the drive first

Lazy writeback

tune2fs -o journal_data_writeback /dev/sdc1

No Journaling

tune2fs -O ^has_journal /dev/sdc1

Now to check what we have

dumpe2fs /dev/sdc1 |grep 'Filesystem features'

Or maybe if you want the whole thing on the screen

dumpe2fs /dev/sdc1 |more

if has_journal option exist when executing the first – you have journal on the file system

And there we are, Now we need to mount it at boot time by adding it to fstab, to do that, we will need the disk’s unique ID !

8- Now executing the following command will give you the unique ID of this new partition for use with fstab (The disk list we will edit below in step 10)
blkid /dev/sdc1
9- create the directory where you want to mount your hard disk, for example
mkdir /hds
mkdir /hds/3tb
10- Now, we add the following line to fstab, notice that noatime increases performance, but some applications might need or rely on it. postfix does not and i have verified that.

UUID=b7a491b1-a690-468f-882f-fbb4ac0a3b53       /hds/3tb            ext4     defaults,noatime                0       1

defaults and noatime are but only a couple of options, here are more options that you can add
nofail = If the disk is not present, continue booting
nobootwait = Limit the amount of time you plan to wait
noauto = Don’t mount it until I issue a “mount /dev/sdb1”, or mount “/hds/thisdisk” command

11- Now execute
mount -a

You are done,. if you execute
df -h
You should see your 2+TB hard drive in there !

To make sure the drive is aligned correctly, i like to write a file on it and see how fast that goes… so let us use a 2GB file

dd if=/dev/zero of=/hds/WD2000_3/deleteme.img bs=1M count=2000

Outcome came out (for a western digital black 2TB)
First run: 2097152000 bytes (2.1 GB) copied, 5.94739 s, 353 MB/s
Consecutive runs: 2097152000 bytes (2.1 GB) copied, 11.1405 s, 188 MB/s
Outcome came out for a western digital green 3TB
First run: 2097152000 bytes (2.1 GB) copied, 8.32337 s, 252 MB/s
Consecutive runs: 2097152000 bytes (2.1 GB) copied, 14.376 s, 146 MB/s

the consecutive runs give close results, what i printed here is the average

Section 1: My hard drive has bad sectors / Blocks / area

Do i need to change it ?
Not necessarily, but If it is in warranty, and they allow you to replace it, a new one is not a bad idea, otherwise read on

it all depends on whether the bad sectors are expanding or not, if they are not, they are probably caused by shock to the hard drive, usually, it is enough to mark them as bad using “chkdsk /r” on windows and leave the drive working.

To find out if your bad sectors are Spreading or not spreading, do a “chkdsk /r” four times, make sure the same number appears in the second and third and fourth time (Forget the first time), then, if the second is different but the third and fourth are the same, then do the test 2 more times, and make sure you get the same number of bad sectors for trials 3, 4, 5, 6, if so, your bad sectors are not spreading.

You did not mention backup in the answer before, do we need to backup ?
People would typically ask you to backup just in case, i say you should always have backup of your most important files, non spreading sectors of the hard drive, in my humble experience do not contribute negatively to reliability, so my answer is, backup should be done regardless

How do i know how many bad sectors are marked on an NTFS hard drive ?
There is a tool called nfi.exe that comes with a bundle Microsoft makes available here http://support.microsoft.com/kb/253066/en-us this tool is part of (OEM Support Tools), it can tell you everything about a disk formatted in NTFS

On a linux box, there is a simple way to search for some text inside a file using regular expressions in the command line

So, the short answer, in Linux, you can simply execute this line

grep -R -B3 -A4 "MYTEXT" /var/ > /root/findingres.txt

this will show you 3 lines before the text and 4 lines after the string and the file name, it will search in the /var/ folder, and will store the searching results to /root/findingres.txt

The above is a simple example, you can use regular expressions to find more complicated stuff

Also, if you want to search the entier hard drive for a string, and you want to search only in one type of file that you want to specify using a file extension you can use the following

grep -R --include=*.txt "MYTEXT" /etc/

Now, if you want to search for a file by file name,

find / -type f -name "myfile.txt"

would look for an exact file name, if you are looking to find a file using wildcards, for example, any file that ends in a certain extension you would

find / -type f -iname "*.psd"

If you want to include directories in your search, remove the -type flag

For some reason, when you look for a way to move a folder and all it’s sub folders into another folder, overwriting the files if they exist on destination, you will find very little information, the reason behind that is that the mv command that both renames files and folders and moves them does not support the -R switch (Recursive), the answer is that you copy them, then delete the source

So, if i downloaded wordpress and i want to update my installation with the new files i would

cp -R /var/vhosts/wordpress/* /var/vhosts/example.com/

this will update my copy of wordpress by moving the contents of the wordpress folder into the virtual hosting directory of my website

KEEP IN MIND THAT THE mv AND cp COMMANDS OVERWRITES WITHOUT PROMPTING….

to make it prompt before overwriting you must provide a -i parameter

If you don’t want a prompt, and you still want to NOT overwrite destination files… you will need to also set the “–reply=no” (depreciated) parameter so that the mv command will answer NO to all overwrite situations

NOTE: –reply has been depreciated (no longer works)

the linux move (mv) command : Moving folders

to move a folder into another folder, assuming there is a file names text.txt inside the folder /hds/ssd/mysql/moveme/text.txt, after this command we will have the file in /hds/ssd/mysql/into/moveme/text.txt

mv /hds/ssd/mysql/moveme/ /hds/ssd/mysql/into/

To move the contents of moveme including sub-folders directly into the folder into without moving the folder moveme itself

mv /hds/ssd/mysql/moveme/* /hds/ssd/mysql/into/

This post is rather old, and everything is secure on the internet these days, so rather than FTP, it is recommended that you setup the new user with SFTP instead (Secure file transfer protocol), SCP is another option, but i have an sftp article ready for you here

So here is a quick guide to setting up a user to have access to a certain directory via FTP

You probably already use a Linux server, you access your files via SFTP or SCP, but you want to give someone access to a certain directory within.

Here is how it is done on a Debian squeeze machine

apt-get install pure-ftpd-common pure-ftpd

Then we need to add a group and default user for our program

groupadd ftpgroup
useradd -g ftpgroup -d /dev/null -s /etc ftpuser

pure-pw useradd test1 -u ftpuser -d /home/ftpusers/test1

pure-pw mkdb

This creates the file mentioned earlier called /etc/pureftpd.pdb, this file houses all information related to your virtual users

pure-pw passwd test1

Once password is set, update the database

pure-pw mkdb

To delete a user

pure-pw userdel test1

pure-pw show test1

pure-ftpwho

Create symlink to add PureDB to authentication methods

cd /etc/pure-ftpd/auth
ln -s ../conf/PureDB 50pure

Disable PAM authentication unless you need it

echo no > /etc/pure-ftpd/conf/PAMAuthentication

Disable UNIX authentication unless you need it

echo no > /etc/pure-ftpd/conf/UnixAuthentication

Today, as i was managing my PLESK Version 9 for Windows server, i noticed that every website i put a tick beside and tried to remove (deleting all files and all related), i ended up disabling and it just won’t get removed

So here is the solution

Open the command prompt
in the command prompt (CMD) change the directory to the plesk bin directory like so

cd c:ParallelsPleskadminbin

Then, execute the command

domain.exe --remove domain.com

You should now find that the domain is no longer in the list of domains.

Sometimes i get an error deleting stating that a file (dll) in system32 directory is in use by…. the answer is reboot the server, then try deleting a few times with the command above until you see the success message

Just like the previous post, the reason why running from the command line works and from the control panel does not work is unknown to me.