Posts Tagged ‘dump’

How to create PCS / Corosync High Availability Cluster config backup and migrate to new Virtual Machines

Thursday, October 26th, 2023

pcs-pcmk-internals-explained-picture

The aim of this article is to illustrate how to literally migrate a an Haproxy PCS Pacemaker / Corosync Cluster configurations from old Virtual Machines that due to time passed become unsupported (The Operating System end of life (EOF)) has reached to a new ones. 
This is quite a complex task especially as you usually need to setup the Hypervisor hosts with VMWare / Xen / KVM / OpenVZ or whatever kind of virtualization is to be used. Then setup the correct network interfaces IPs failover the heartbeat lines over which the cluster will work to prevent Split Brain scenartions, the Network Bonding interfaces to guarantee a higher amount of higher availability as well as physically install and update all the cluster software on the new built Linux hosts that will be members of the new cluster in setup. 

All this configuration from scratch of a PCS Corosync cluster is a very lenght topic which I'll try to cover in some of my next articles. In short to migrate the cluster from old machines to new once all this predescribed steps are in line. 
You will need to.


1. Create backup of old cluster configuration
2. Migrate the backup to a new built VM Machine hosts
3. Import the cluster configuration into the PCS Cluster.


Bear in mind that this article discusses a migration of CentOS Linux release 7.9.2009 with its shipped versions of corosync / pacemaker and pcs 

How to create cluster config backup and migrate to new VM

1. Dump cluster assuming that is a Quality Assuare or Pre – Production host  to create full cluster config backup

[root@old-cluster-machine ~]# pcs config backup old-cluster-machine.pcs.config.bak

2. Dump cluster Production full configuration

[root@old-cluster-machine1 ~]# pcs config backup old-cluster-machine1.pcs.config.bak

This command will output a backup of 

old-cluster-machine1.pcs.config.bak.tar.bz2

3. Migrate a cluster identical config to the new Virtual machines

Usually this moval of produced backup files with pcs config backup  commands can be copied with something like FTP / SFTP  or SSL-ed / TLS-ed protocol. However if you have to move the configuration files from a paranoid Citrix environment that doesn't allow you to have any SFTP / SSH or FTP kind of transfer protocol from the location where the old config lays to the new ones. 
A simple encoding of the binary format dumped configuration to plain text files can be done and files, can be moved via a simple copy / paste operation (a bit of a hack) 🙂

Encode the cluster config to be able to migrate configuration in plain text via a simple Copy / Paste operation.

 

[root@old-cluster-machine ~]# base64 config backup old-cluster-machine.pcs.config.bak > old-cluster-machine.pcs.config.bak.tgz.b64

[root@old-cluster-machine1 ~]# base64 old-cluster-machine1.pcs.config.bak.tar.bz2 > old-cluster-machine1.pcs.config.bak.tgz.b64
[root@old-cluster-machine ~]# cat  old-cluster-machine.pcs.config.bak.tgz.b64

(Copy output and Paste to new host VM) /root/haproxy-cluster-backup)

[root@old-cluster-machine1 ~]# cat old-cluster-machine1.pcs.config.bak.tgz.b64 


(Copy output and Paste to new host VM) /root/haproxy-cluster-backup)

Login to the new hosts, where configs has to be migrated and restore the files with base64

For QA / Preprod to restore backup config

[root@dkv-newqa-vm ~]# mkdir /root/haproxy-cluster-backup
[root@dkv-newqa-vm ~]# cd /root/haproxy-cluster-backup
[root@dkv-newqa-vm ~]# base64 -d old-cluster-machine.config.bak.tgz.b64 > old-cluster-machine.pcs.config.bak.tar.bz2
[root@dkv-newqa-vm ~]#  tar -jxvf old-cluster-machine.pcs.config.bak.tar.bz2
ak.tar.bz2
version.txt
pcs_settings.conf
corosync.conf
cib.xml
pacemaker_authkey
uidgid.d/

 

For Prod to restore backup config

[root@dkv-newprod-vm  ~]# mkdir /root/haproxy-cluster-backup
[root@dkv-newprod-vm ~]# cd /root/haproxy-cluster-backup
[root@dkv-newprod-vm ~]# base64 -d old-cluster-machine.config.bak.tgz.b64 > old-cluster-machine1.pcs.config.bak.tar.bz2
ak.tar.bz2
version.txt
pcs_settings.conf
corosync.conf
cib.xml
pacemaker_authkey
uidgid.d/


N!B! An Useful hin is on RHEL 8 Linux's shipped pcs command version has also a very useful command with which you can simply dump completly the config of the cluster in straight commands which you can run directly on the new VM machines where you have migrated.

The command to print out commands that would add existing cluster resources on Redhat 8:

# pcs resource config –output-format=cmd

Another useful command for cluster migration is cibadmin

i.e. to dump cluster xml config

#cibadmin –q > cluster.xml

Later you can import the prior xml dump with it.

# cibadmin –replace –xml-file cib.xml

 

How to test RAM Memory for errors in Linux / UNIX OS servers. Find broken memory RAM banks

Friday, December 3rd, 2021

test-ram-memory-for-errors-linux-unix-find-broken-memory-logo

 

1. Testing the memory with motherboard integrated tools
 

Memory testing has been integral part of Computers for the last 50 years. In the dawn of computers those older perhaps remember memory testing was part of the computer initialization boot. And this memory testing was delaying the boot with some seconds and the user could see the memory numbers being counted up to the amount of memory. With the increased memory modern computers started to have and the annoyance to wait for a memory check program to check the computer hardware memory on modern computers this check has been mitigated or completely removed on some hardware.
Thus under some circumstances sysadmins or advanced computer users might need to check the memory, especially if there is some suspicion for memory damages or if for example a home PC starts crashing with Blue screens of Death on Windows without reason or simply the PC or some old arcane Linux / UNIX servers gets restarted every now and then for now apparent reason. When such circumstances occur it is an idea to start debugging the hardware issue with a simple memory check.

There are multiple ways to test installed memory banks on a server laptop or local home PC both integrated and using external programs.
On servers that is usually easily done from ILO or IPMI or IDRAC access (usually web) interface of the vendor, on laptops and home usage from BIOS or UEFI (Unified Extensible Firmware Interface) acces interface on system boot that is possible as well.

memtest-hp
HP BIOS Setup

An old but gold TIP, more younger people might not know is the

 

Prolonged SHIFT key press which once held with the user instructs the machine to initiate a memory test before the computer starts reading what is written in the boot loader.

So before anything else from below article it might be a good idea to just try HOLD SHIFT for 15-20 seconds after a complete Shut and ON from the POWER button.

If this test does not triggered or it is triggered and you end up with some corrupted memory but you're not sure which exact Memory bank is really crashing and want to know more on what memory Bank and segments are breaking up you might want to do a more thorough testing. In below article I'll try to explain shortly how this can be done.


2. Test the memory using a boot USB Flash Drive / DVD / CD 
 

Say hello to memtest86+. It is a Linux GRUB boot loader bootable utility that tests physical memory by writing various patterns to it and reading them back. Since memtest86+ runs directly off the hardware it does not require any operating system support for execution. Perhaps it is important to mention that memtest86 (is PassMark memtest86)and memtest86+ (An Advanced Memory diagnostic tool) are different tools, the first is freeware and second one is FOSS software.

To use it all you'll need is some version of Linux. If you don't already have some burned in somewhere at your closet, you might want to burn one.
For Linux / Mac users this is as downloading a Linux distribution ISO file and burning it with

# dd if=/path/to/iso of=/dev/sdbX bs=80M status=progress


Windows users can burn a Live USB with whatever Linux distro or download and burn the latest versionof memtest86+ from https://www.memtest.org/  on Windows Desktop with some proggie like lets say UnetBootIn.
 

2.1. Run memtest86+ on Ubuntu

Many Linux distributions such as Ubuntu 20.0 comes together with memtest86+, which can be easily invoked from GRUB / GRUB2 Kernel boot loader.
Ubuntu has a separate menu pointer for a Memtest.

ubuntu-grub-2-04-boot-loader-memtest86-menu-screenshot

Other distributions RPM based distributions such as CentOS, Fedora Linux, Redhat things differ.

2.2. memtest86+ on Fedora


Fedora used to have the memtest86+ menu at the GRUB boot selection prompt, but for some reason removed it and in newest Fedora releases as of time such as Fedora 35 memtest86+ is preinstalled and available but not visible, to start on  already and to start a memtest memory test tool:

  •   Boot a Fedora installation or Rescue CD / USB. At the prompt, type "memtest86".

boot: memtest86

2.3 memtest86+ on RHEL Linux

The memtest86+tool is available as an RPM package from Red Hat Network (RHN) as well as a boot option from the Red Hat Enterprise Linux rescue disk.
And nowadays Red Hat Enterprise Linux ships by default with the tool.

Prior redhat (now legacy) releases such as on RHEL 5.0 it has to be installed and configure it with below 3 commands.

[root@rhel ~]# yum install memtest86+
[root@rhel ~]# memtest-setup
[root@rhel ~]# grub2-mkconfig -o /boot/grub2/grub.cfg


    Again as with CentOS to boot memtest86+ from the rescue disk, you will need to boot your system from CD 1 of the Red Hat Enterprise Linux installation media, and type the following at the boot prompt (before the Linux kernel is started):

boot: memtest86

memtestx86-8gigabytes-of-memory-boot-screenshot
memtest86+ testing 5 memory slots

As you see all on above screenshot the Memory banks are listed as Slots. There are a number of Tests to be completed until
it can be said for sure memory does not have any faulty cells. 
The

Pass: 0
Errors: 0 

Indicates no errors, so in the end if memtest86 does not find anything this values should stay at zero.
memtest86+ is also usable to detecting issues with temperature of CPU. Just recently I've tested a PC thinking that some memory has defects but it turned out the issue on the Computer was at the CPU's temperature which was topping up at 80 – 82 Celsius.

If you're unfortunate and happen to get some corrupted memory segments you will get some red fields with the memory addresses found to have corrupted on Read / Write test operations:

memtest86-returning-memory-address-errors-screenshot


2.4. Install and use memtest and memtest86+ on Debian / Mint Linux

You can install either memtest86+ or just for the fun put both of them and play around with both of them as they have a .deb package provided out of debian non-free /etc/apt/sources.list repositories.


root@jeremiah:/home/hipo# apt-cache show memtest86 memtest86+
Package: memtest86
Version: 4.3.7-3
Installed-Size: 302
Maintainer: Yann Dirson <dirson@debian.org>
Architecture: amd64
Depends: debconf (>= 0.5) | debconf-2.0
Recommends: memtest86+
Suggests: hwtools, memtester, kernel-patch-badram, grub2 (>= 1.96+20090523-1) | grub (>= 0.95+cvs20040624), mtools
Description-en: thorough real-mode memory tester
 Memtest86 scans your RAM for errors.
 .
 This tester runs independently of any OS – it is run at computer
 boot-up, so that it can test *all* of your memory.  You may want to
 look at `memtester', which allows testing your memory within Linux,
 but this one won't be able to test your whole RAM.
 .
 It can output a list of bad RAM regions usable by the BadRAM kernel
 patch, so that you can still use you old RAM with one or two bad bits.
 .
 This is the last DFSG-compliant version of this software, upstream
 has opted for a proprietary development model starting with 5.0.  You
 may want to consider using memtest86+, which has been forked from an
 earlier version of memtest86, and provides a different set of
 features.  It is available in the memtest86+ package.
 .
 A convenience script is also provided to make a grub-legacy-based
 floppy or image.

Description-md5: 0ad381a54d59a7d7f012972f613d7759
Homepage: http://www.memtest86.com/
Section: misc
Priority: optional
Filename: pool/main/m/memtest86/memtest86_4.3.7-3_amd64.deb
Size: 45470
MD5sum: 8dd2a4c52910498d711fbf6b5753bca9
SHA256: 09178eca21f8fd562806ccaa759d0261a2d3bb23190aaebc8cd99071d431aeb6

Package: memtest86+
Version: 5.01-3
Installed-Size: 2391
Maintainer: Yann Dirson <dirson@debian.org>
Architecture: amd64
Depends: debconf (>= 0.5) | debconf-2.0
Suggests: hwtools, memtester, kernel-patch-badram, memtest86, grub-pc | grub-legacy, mtools
Description-en: thorough real-mode memory tester
 Memtest86+ scans your RAM for errors.
 .
 This tester runs independently of any OS – it is run at computer
 boot-up, so that it can test *all* of your memory.  You may want to
 look at `memtester', which allows to test your memory within Linux,
 but this one won't be able to test your whole RAM.
 .
 It can output a list of bad RAM regions usable by the BadRAM kernel
 patch, so that you can still use your old RAM with one or two bad bits.
 .
 Memtest86+ is based on memtest86 3.0, and adds support for recent
 hardware, as well as a number of general-purpose improvements,
 including many patches to memtest86 available from various sources.
 .
 Both memtest86 and memtest86+ are being worked on in parallel.
Description-md5: aa685f84801773ef97fdaba8eb26436a
Homepage: http://www.memtest.org/

Tag: admin::benchmarking, admin::boot, hardware::storage:floppy,
 interface::text-mode, role::program, scope::utility, use::checking
Section: misc
Priority: optional
Filename: pool/main/m/memtest86+/memtest86+_5.01-3_amd64.deb
Size: 75142
MD5sum: 4f06523532ddfca0222ba6c55a80c433
SHA256: ad42816e0b17e882713cc6f699b988e73e580e38876cebe975891f5904828005
 

 

root@jeremiah:/home/hipo# apt-get install –yes memtest86+

root@jeremiah:/home/hipo# apt-get install –yes memtest86

Reading package lists… Done
Building dependency tree       
Reading state information… Done
Suggested packages:
  hwtools kernel-patch-badram grub2 | grub
The following NEW packages will be installed:
  memtest86
0 upgraded, 1 newly installed, 0 to remove and 21 not upgraded.
Need to get 45.5 kB of archives.
After this operation, 309 kB of additional disk space will be used.
Get:1 http://ftp.de.debian.org/debian buster/main amd64 memtest86 amd64 4.3.7-3 [45.5 kB]
Fetched 45.5 kB in 0s (181 kB/s)     
Preconfiguring packages …
Selecting previously unselected package memtest86.
(Reading database … 519985 files and directories currently installed.)
Preparing to unpack …/memtest86_4.3.7-3_amd64.deb …
Unpacking memtest86 (4.3.7-3) …
Setting up memtest86 (4.3.7-3) …
Generating grub configuration file …
Found background image: saint-John-of-Rila-grub.jpg
Found linux image: /boot/vmlinuz-4.19.0-18-amd64
Found initrd image: /boot/initrd.img-4.19.0-18-amd64
Found linux image: /boot/vmlinuz-4.19.0-17-amd64
Found initrd image: /boot/initrd.img-4.19.0-17-amd64
Found linux image: /boot/vmlinuz-4.19.0-8-amd64
Found initrd image: /boot/initrd.img-4.19.0-8-amd64
Found linux image: /boot/vmlinuz-4.19.0-6-amd64
Found initrd image: /boot/initrd.img-4.19.0-6-amd64
Found linux image: /boot/vmlinuz-4.19.0-5-amd64
Found initrd image: /boot/initrd.img-4.19.0-5-amd64
Found linux image: /boot/vmlinuz-4.9.0-8-amd64
Found initrd image: /boot/initrd.img-4.9.0-8-amd64
Found memtest86 image: /boot/memtest86.bin
Found memtest86+ image: /boot/memtest86+.bin
Found memtest86+ multiboot image: /boot/memtest86+_multiboot.bin
File descriptor 3 (pipe:[66049]) leaked on lvs invocation. Parent PID 22581: /bin/sh
done
Processing triggers for man-db (2.8.5-2) …

 

After this both memory testers memtest86+ and memtest86 will appear next to the option of booting a different version kernels and the Advanced recovery kernels, that you usually get in the GRUB boot prompt.

2.5. Use memtest embedded tool on any Linux by adding a kernel variable

Edit-Grub-Parameters-add-memtest-4-to-kernel-boot

2.4.1. Reboot your computer

# reboot

2.4.2. At the GRUB boot screen (with UEFI, press Esc).

2.4.3 For 4 passes add temporarily the memtest=4 kernel parameter.
 

memtest=        [KNL,X86,ARM,PPC,RISCV] Enable memtest
                Format: <integer>
                default : 0 <disable>
                Specifies the number of memtest passes to be
                performed. Each pass selects another test
                pattern from a given set of patterns. Memtest
                fills the memory with this pattern, validates
                memory contents and reserves bad memory
                regions that are detected.


3. Install and use memtester Linux tool
 

At some condition, memory is the one of the suspcious part, or you just want have a quick test. memtester  is an effective userspace tester for stress-testing the memory subsystem.  It is very effective at finding intermittent and non-deterministic faults.

The advantage of memtester "live system check tool is", you can check your system for errors while it's still running. No need for a restart, just run that application, the downside is that some segments of memory cannot be thoroughfully tested as you already have much preloaded data in it to have the Operating Sytstem running, thus always when possible try to stick to rule to test the memory using memtest86+  from OS Boot Loader, after a clean Machine restart in order to clean up whole memory heap.

Anyhow for a general memory test on a Critical Legacy Server  (if you lets say don't have access to Remote Console Board, or don't trust the ILO / IPMI Hardware reported integrity statistics), running memtester from already booted is still a good idea.


3.1. Install memtester on any Linux distribution from source

wget http://pyropus.ca/software/memtester/old-versions/memtester-4.2.2.tar.gz
# tar zxvf memtester-4.2.2.tar.gz
# cd memtester-4.2.2
# make && make install

3.2 Install on RPM based distros

 

On Fedora memtester is available from repositories however on many other RPM based distros it is not so you have to install it from source.

[root@fedora ]# yum install -y memtester

 

3.3. Install memtester on Deb based Linux distributions from source
 

To install it on Debian / Ubuntu / Mint etc. , open a terminal and type:
 

root@linux:/ #  apt install –yes memtester

The general run syntax is:

memtester [-p PHYSADDR] [ITERATIONS]


You can hence use it like so:

hipo@linux:/ $ sudo memtester 1024 5

This should allocate 1024MB of memory, and repeat the test 5 times. The more repeats you run the better, but as a memtester run places a great overall load on the system you either don't increment the runs too much or at least run it with  lowered process importance e.g. by nicing the PID:

hipo@linux:/ $ nice -n 15 sudo memtester 1024 5

 

  • If you have more RAM like 4GB or 8GB, it is upto you how much memory you want to allocate for testing.
  • As your operating system, current running process might take some amount of RAM, Please check available Free RAM and assign that too memtester.
  • If you are using a 32 Bit System, you cant test more than 4 GB even though you have more RAM( 32 bit systems doesnt support more than 3.5 GB RAM as you all know).
  • If your system is very busy and you still assigned higher than available amount of RAM, then the test might get your system into a deadlock, leads to system to halt, be aware of this.
  • Run the memtester as root user, so that memtester process can malloc the memory, once its gets hold on that memory it will try to apply lock. if specified memory is not available, it will try to reduce required RAM automatically and try to lock it with mlock.
  • if you run it as a regular user, it cant auto reduce the required amount of RAM, so it cant lock it, so it tries to get hold on that specified memory and starts exhausting all system resources.


If you have 8 Gigas of RAM plugged into the PC motherboard you have to multiple 1024*8 this is easily done with bc (An arbitrary precision calculator language) tool:

root@linux:/ # bc -l
bc 1.07.1
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006, 2008, 2012-2017 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'. 
8*1024
8192


 for example you should run:

root@linux:/ # memtester 8192 5

memtester version 4.3.0 (64-bit)
Copyright (C) 2001-2012 Charles Cazabon.
Licensed under the GNU General Public License version 2 (only).

pagesize is 4096
pagesizemask is 0xfffffffffffff000
want 8192MB (2083520512 bytes)
got  8192MB (2083520512 bytes), trying mlock …Loop 1/1:
  Stuck Address       : ok        
  Random Value        : ok
  Compare XOR         : ok
  Compare SUB         : ok
  Compare MUL         : ok
  Compare DIV         : ok
  Compare OR          : ok
  Compare AND         : ok
  Sequential Increment: ok
  Solid Bits          : ok        
  Block Sequential    : ok        
  Checkerboard        : ok        
  Bit Spread          : ok        
  Bit Flip            : ok        
  Walking Ones        : ok        
  Walking Zeroes      : ok        
  8-bit Writes        : ok
  16-bit Writes       : ok

Done.

 

4. Shell Script to test server memory for corruptions
 

If for some reason the machine you want to run a memory test doesn't have connection to the external network such as the internet and therefore you cannot configure a package repository server and install memtester, the other approach is to use a simple memory test script such as memtestlinux.sh
 

#!/bin/bash
# Downloaded from https://www.srv24x7.com/memtest-linux/
echo "ByteOnSite Memory Test"
cpus=`cat /proc/cpuinfo | grep processor | wc -l`
if [ $cpus -lt 6 ]; then
threads=2
else
threads=$(($cpus / 2))
fi
echo "Detected $cpus CPUs, using $threads threads.."
memory=`free | grep 'Mem:' | awk {'print $2'}`
memoryper=$(($memory / $threads))
echo "Detected ${memory}K of RAM ($memoryper per thread).."
freespace=`df -B1024 . | tail -n1 | awk {'print $4'}`
if [ $freespace -le $memory ]; then
echo You do not have enough free space on the current partition. Minimum: $memory bytes
exit 1
fi
echo "Clearing RAM Cache.."
sync; echo 3 > /proc/sys/vm/drop_cachesfile
echo > dump.memtest.img
echo "Writing to dump file (dump.memtest.img).."
for i in `seq 1 $threads`;
do
# 1044 is used in place of 1024 to ensure full RAM usage (2% over allocation)
dd if=/dev/urandom bs=$memoryper count=1044 >> dump.memtest.img 2>/dev/null &
pids[$i]=$!
echo $i
done
for pid in "${pids[@]}"
do
wait $pid
done

echo "Reading and analyzing dump file…"
echo "Pass 1.."
md51=`md5sum dump.memtest.img | awk {'print $1'}`
echo "Pass 2.."
md52=`md5sum dump.memtest.img | awk {'print $1'}`
echo "Pass 3.."
md53=`md5sum dump.memtest.img | awk {'print $1'}`
if [ “$md51” != “$md52” ]; then
fail=1
elif [ “$md51” != “$md53” ]; then
fail=1
elif [ “$md52” != “$md53” ]; then
fail=1
else
fail=0
fi
if [ $fail -eq 0 ]; then
echo "Memory test PASSED."
else
echo "Memory test FAILED. Bad memory detected."
fi
rm -f dump.memtest.img
exit $fail

Nota Bene !: Again consider the restults might not always be 100% trustable if possible restart the server and test with memtest86+

Consider also its important to make sure prior to script run,  you''ll have enough disk space to produce the dump.memtest.img file – file is created as a test bed for the memory tests and if not scaled properly you might end up with a full ( / ) root directory!

 

4.1 Other memory test script with dd and md5sum checksum

I found this solution on the well known sysadmin site nixCraft cyberciti.biz, I think it makes sense and quicker.

First find out memory site using free command.
 

# free
             total       used       free     shared    buffers     cached
Mem:      32867436   32574160     293276          0      16652   31194340
-/+ buffers/cache:    1363168   31504268
Swap:            0          0          0


It shows that this server has 32GB memory,
 

# dd if=/dev/urandom bs=32867436 count=1050 of=/home/memtest


free reports by k and use 1050 is to make sure file memtest is bigger than physical memory.  To get better performance, use proper bs size, for example 2048 or 4096, depends on your local disk i/o,  the rule is to make bs * count > 32 GB.
run

# md5sum /home/memtest; md5sum /home/memtest; md5sum /home/memtest


If you see md5sum mismatch in different run, you have faulty memory guaranteed.
The theory is simple, the file /home/memtest will cache data in memory by filling up all available memory during read operation. Using md5sum command you are reading same data from memory.


5. Other ways to test memory / do a machine stress test

Other good tools you might want to check for memory testing is mprime – ftp://mersenne.org/gimps/ 
(https://www.mersenne.org/ftp_root/gimps/)

  •  (mprime can also be used to stress test your CPU)

Alternatively, use the package stress-ng to run all kind of stress tests (including memory test) on your machine.
Perhaps there are other interesting tools for a diagnosis of memory if you know other ones I miss, let me know in the comment section.

Linux: List last 10 (newest) and 10 oldest modified files in a directory with ls

Tuesday, April 8th, 2014

An useful thing on GNU / Linux sometimes is to list last or oldest modified files in directory.

Lets say you want to list last 10 modified files with ls from today / yesterday. Here is how:
 

ls -1t | head -10
my.cnf
wordperss_enabled_plugins.txt
newcerts/
mysql-hipo_pcfreakbiz.dump
NewArchive-Jan-10-15.zip
hipo_pcfreakbiz-mysqldb-any-out-1389361234.tgz
Tisho_Snimki/
wordpress/
wp-cron.php?doing_wp_cron=1.1
wp-cron.php

 

To list 10 oldest modified files on Linux:

 

ls -1t | tail -10
    my.cnf
    pcfreak_sql-15_10_05_2012
    mysql-tuning-primer*
    tuning-primer.sh*
    system-administration-services.html
    blog_backup_15_07_2012.tar.gz
    www-files/
    dump.sql
    courier-imap*
    djbdns-1.05.tar.gz


Cheers 😉

How to copy / clone installed packages from one Debian server to another

Friday, April 13th, 2012

1. Dump all installed server packages from Debian Linux server1

First it is necessery to dump a list of all installed packages on the server from which the intalled deb packages 'selection' will be replicated.

debian-server1:~# dpkg --get-selections \* > packages.txt

The format of the produced packages.txt file will have only two columns, in column1 there will be the package (name) installed and in column 2, the status of the package e.g.: install or deinstall

Note that you can only use the –get-selections as root superuser, trying to run it with non-privileged user I got:

hipo@server1:~$ dpkg --set-selections > packages.txt
dpkg: operation requires read/write access to dpkg status area

2. Copy packages.txt file containing the installed deb packages from server1 to server2

There is many way to copy the packages.txt package description file, one can use ftp, sftp, scp, rsync … lftp or even copy it via wget if placed in some Apache directory on server1.

A quick and convenient way to copy the file from Debian server1 to server2 is with scp as it can also be used easily for an automated script to do the packages.txt file copying (if for instance you have to implement package cloning on multiple Debian Linux servers).

root@debian-server1:~# scp ./packages.txt hipo@server-hostname2:~/packages.txt
The authenticity of host '83.170.97.153 (83.170.97.153)' can't be established. RSA key fingerprint is 38:da:2a:79:ad:38:5b:64:9e:8b:b4:81:09:cd:94:d4. Are you sure you want to continue connecting (yes/no)? yes Warning: Permanently added '83.170.97.153' (RSA) to the list of known hosts. hipo@83.170.97.153's password:
packages.txt

As this is the first time I make connection to server2 from server1, I'm prompted to accept the host RSA unique fingerprint.

3. Install the copied selection from server1 on server2 with apt-get or dselect

debian-server2:/home/hipo# apt-get update
...
debian-server2:/home/hipo# apt-get upgrade
Reading package lists... Done
Building dependency tree
Reading state information... Done
debian-server2:/home/hipo# dpkg --set-selections < packages.txt
debian-server2:/home/hipo# apt-get -u dselect-upgrade --yes

The first apt-get update command assures the server will have the latest version of the packages currently installed, this will save you from running an outdated versions of the installed packages on debian-server2

Bear in mind that using apt-get sometimes, might create dependency issues. This is depending on the exact package names, being replicated in between the servers

Therefore it is better to use another approach with bash for loop to "replicate" installed packages between two servers, like so:

debian-server2:/home/hipo# for i in $(cat packages.txt |awk '{ print $1 }'); do aptitude install $i; done

If you want to automate the questioning about aptitude operations pass on the -y

debian-server2:/home/hipo# for i in $(cat packages.txt |awk '{ print $1 }'); do aptitude -y install $i; done

Be cautious if the -y is passed as sometimes some packages might be removed from the server to resolve dependency issues, if you need this packages you will have to again install them manually.

4. Mirroring package selection from server1 to server2 using one liner

A quick one liner, that does replicate a set of preselected packages from server1 to server2 is also possible with either a combination of apt, ssh, awk and dpkg or with ssh + dpkg + dselect :

a) One-liner code with apt-get unifying the installed packages between 2 or more servers

debian-server2:~# apt-get --yes install `ssh root@debian-server1 "dpkg -l | grep -E ^ii" | awk '{print $2}'`
...

If it is necessery to install on more than just debian-server2, copy paste the above code to all servers you want to have identical installed packages as with debian-server1 or use a shor for loop to run the commands for each and every host of multiple servers group.

In some cases it might be better to use dselect instead as in some situations using apt-get might not correctly solve the package dependencies, if encountering problems with dependencies better run:

debian-server2:/home/hipo# ssh root@debian-server1 'dpkg --get-selections' | dpkg --set-selections && dselect install

As you can see using this second dselect installed "package" mirroring is also way easier to read and understand than the prior "cryptic" method with apt-get, hence I personally think using dselect method is a better.

Well that's basically it. If you need to synchronize also configurations, either an rsync/scp shell script, should be used with all defined server1 config files or in case if a cloning of packages between identical server machines is necessery dd or some other tool like Norton Ghost could be used.
Hope this helps, someone.

Tiny PHP script to dump your browser set HTTP headers (useful in debugging)

Friday, March 30th, 2012

While browsing I stumbled upon a nice blog article

Dumping HTTP headers

The arcitle, points at few ways to DUMP the HTTP headers obtained from user browser.
As I'm not proficient with Ruby, Java and AOL Server what catched my attention is a tiny php for loop, which loops through all the HTTP_* browser set variables and prints them out. Here is the PHP script code:

<?php<br />
foreach($_SERVER as $h=>$v)<br />
if(ereg('HTTP_(.+)',$h,$hp))<br />
echo "<li>$h = $v</li>\n";<br />
header('Content-type: text/html');<br />
?>

The script is pretty easy to use, just place it in a directory on a WebServer capable of executing php and save it under a name like:
show_HTTP_headers.php

If you don't want to bother copy pasting above code, you can also download the dump_HTTP_headers.php script here , rename the dump_HTTP_headers.php.txt to dump_HTTP_headers.php and you're ready to go.

Follow to the respective url to exec the script. I've installed the script on my webserver, so if you are curious of the output the script will be returning check your own browser HTTP set values by clicking here.
PHP will produce output like the one in the screenshot you see below, the shot is taken from my Opera browser:

Screenshot show HTTP headers.php script Opera Debian Linux

Another sample of the text output the script produce whilst invoked in my Epiphany GNOME browser is:

HTTP_HOST = www.pc-freak.net
HTTP_USER_AGENT = Mozilla/5.0 (X11; U; Linux x86_64; en-us) AppleWebKit/531.2+ (KHTML, like Gecko) Version/5.0 Safari/531.2+ Debian/squeeze (2.30.6-1) Epiphany/2.30.6
HTTP_ACCEPT = application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
HTTP_ACCEPT_ENCODING = gzip
HTTP_ACCEPT_LANGUAGE = en-us, en;q=0.90
HTTP_COOKIE = __qca=P0-2141911651-1294433424320;
__utma_a2a=8614995036.1305562814.1274005888.1319809825.1320152237.2021;wooMeta=MzMxJjMyOCY1NTcmODU1MDMmMTMwODQyNDA1MDUyNCYxMzI4MjcwNjk0ODc0JiYxMDAmJjImJiYm; 3ec0a0ded7adebfeauth=22770a75911b9fb92360ec8b9cf586c9;
__unam=56cea60-12ed86f16c4-3ee02a99-3019;
__utma=238407297.1677217909.1260789806.1333014220.1333023753.1606;
__utmb=238407297.1.10.1333023754; __utmc=238407297;
__utmz=238407297.1332444980.1586.413.utmcsr=www.pc-freak.net|utmccn=(referral)|utmcmd=referral|utmcct=/blog/

You see the script returns, plenty of useful information for debugging purposes:
HTTP_HOST – Virtual Host Webserver name
HTTP_USER_AGENT – The browser exact type useragent returnedHTTP_ACCEPT – the type of MIME applications accepted by the WebServerHTTP_ACCEPT_LANGUAGE – The language types the browser has support for
HTTP_ACCEPT_ENCODING – This PHP variable is usually set to gzip or deflate by the browser if the browser has support for webserver returned content gzipping.
If HTTP_ACCEPT_ENCODING is there, then this means remote webserver is configured to return its HTML and static files in gzipped form.
HTTP_COOKIE – Information about browser cookies, this info can be used for XSS attacks etc. 🙂
HTTP_COOKIE also contains the referrar which in the above case is:
__utmz=238407297.1332444980.1586.413.utmcsr=www.pc-freak.net|utmccn=(referral)
The Cookie information HTTP var also contains information of the exact link referrar:
|utmcmd=referral|utmcct=/blog/

For the sake of comparison show_HTTP_headers.php script output from elinks text browser is like so:

* HTTP_HOST = www.pc-freak.net
* HTTP_USER_AGENT = Links (2.3pre1; Linux 2.6.32-5-amd64 x86_64; 143x42)
* HTTP_ACCEPT = */*
* HTTP_ACCEPT_ENCODING = gzip,deflate * HTTP_ACCEPT_CHARSET = us-ascii, ISO-8859-1, ISO-8859-2, ISO-8859-3, ISO-8859-4, ISO-8859-5, ISO-8859-6, ISO-8859-7, ISO-8859-8, ISO-8859-9, ISO-8859-10, ISO-8859-13, ISO-8859-14, ISO-8859-15, ISO-8859-16, windows-1250, windows-1251, windows-1252, windows-1256,
windows-1257, cp437, cp737, cp850, cp852, cp866, x-cp866-u, x-mac, x-mac-ce, x-kam-cs, koi8-r, koi8-u, koi8-ru, TCVN-5712, VISCII,utf-8 * HTTP_ACCEPT_LANGUAGE = en,*;q=0.1
* HTTP_CONNECTION = keep-alive
One good reason, why it is good to give this script a run is cause it can help you reveal problems with HTTP headers impoperly set cookies, language encoding problems, security holes etc. Also the script is a good example, for starters in learning PHP programming.

 

List and get rid of obsolete program core dump files and completely disable core files on FreeBSD

Tuesday, November 1st, 2011

My FreeBSD router has started running out of space, I looked for ways to clean up some space. So I remembered some programs are generating core files while they crash. Some of these files are really huge and ban be from 1Mb to > 1G.

I used find to first list all my produced core files starting from root directory (/) , like so:

find / -name core -exec du -hsc {} ;
....

Having a list of my core files with the respective core file size and after reviewing, I deleted one by one the cores which were there just taking up space.
It’s a wise idea that core dumps file generation on program crash is completely disabled, however I forgot to disable cores, so I had plenty of the cores – (crash files which are handy for debug purposes and fixing the bug that caused the crash).

Further on I used an /etc/rc.confdumpdev=NO , variable which instructs the kernel to not generate core files on program crash:

freebsd# echo 'dumpdev=NO' >> /etc/rc.conf

Next, to make dumpdev=NO , take affect I rebooted the server:

freebsd# shutdown -r now
...

There is a way to instruct every server running daemon to know about the newly set dumpdev=NO by restarting each of the services with their init scripts individually, but I was too lazy to do that.