Monitoring a bottleneck with strace

Posted on by David Saliba

If let’s say Mysql is slow at performing a task you can check what is the bottleneck using strace to attach to the process.

<span style="color: #00ff00;">$ ps -ef|grep -i mysql</span>

Identify the process id then

<span style="color: #00ff00;">$ strace -cp &lt;pid&gt;</span>

Leave it 10 seconds or a minute then ^C. That will tell you where the process is spending its time, e.g. it could just be waiting for the disk if you seen read and write dominate.

Njoy 🙂

Start Teamviewer from an ssh session remotely

Posted on by David Saliba

So you remote deskptop rebooted and teamviewer did not run on startup as it does not do in Linux for some strange reason:

Connect with ssh ( putty)

Then run

DISPLAY=`localhost`:0 teamviewer&

Njoy 🙂 !

Enable VMWare time sync from command line

Posted on by David Saliba

Virtual machines and NTP do not go easily well together. Machines paused for extended periods tend to loose the ntp sync since the difference grows too much.

 

Also from VMware Docs the following info might be clarificatory:

  • Do not configure the virtual machine to synchronize to its own (virtual) hardware clock, not even as a fallback with a high stratum number. Some sample ntpd.conf files contain a section specifying the local clock as a potential time server, often marked with the comment “undisciplined local clock.” Delete any such server specification from your ntpd.conf file.
  • Include the option tinker panic 0 at the top of your ntp.conf file. By default, the NTP daemon sometimes panics and exits if the underlying clock appears to be behaving erratically. This option causes the daemon to keep running instead of panicking.
  • Follow standard best practices for NTP: Choose a set of servers to synchronize to that have accurate time and adequate redundancy. If you have many virtual or physical client machines to synchronize, set up some internal servers for them to use, so hat all your clients are not directly accessing an external low-stratum NTP server and overloading it with requests

And :

In ESX, the ESX NTP daemon runs in the service console. Because the service console is partially virtualized, with the VMkernel in direct control of the hardware, NTP running on the service console provides less precise time than in configurations where it runs directly on a host operating system. Therefore, if you are using native synchronization software in your virtual machines, it is somewhat preferable to synchronize them over the network from an NTP server that is running directly on its host kernel, not to the NTP server in the service console. In ESXi, there is no service console and the NTP daemon runs directly on the VMkernel, so it works well as a NTP server for virtual machines.

Quoted from : http://www.vmware.com/files/pdf/techpaper/Timekeeping-In-VirtualMachines.pdf

Easy way (And I think best solution is)

  1. Setup NTP client to ESX
  2. Install VMWARE tools on the Guests ( recommended anyways).
  3. In Linux ( cause that’s what we care about ) run vmware-toolbox-cmd timesync enable

To force a sync run hwclock command.

nJoy 🙂 !

 

 

How to add a disk to LVM

Posted on by David Saliba

Suppose the Disk is /dev/sdb, the second scsi disk,

   fdisk /dev/sdb
   create as many partitions as you need using command n
   Label them with command t as 8e for making it Linux LVM
   Write and Exit with the command w.

Format the partitions you require using mkfs command

   mkfs -t ext3 -c /dev/sdb1

LVM commands

   pvcreate /dev/sdb1
   vgextend VolGroup00 /dev/sdb1
   lvextend -L 15G /dev/VolGroup00/LogVol01 ;for extending LogVol to 15GB
   lvextend -L+1G /dev/VolGroup00/LogVol01 ;for adding one more GB to Logical Volume LogVol01
   lvextend -l +100%FREE /dev/VolGroup00/LogVol01


Next you shall need to resize the filesystem.


   resize2fs -l /dev/VolGroup00/LogVol01


Thats it finished Njoy  🙂 !

        

        


	






    


        
		
Test if memcache is installed in php from bash line

        

            Posted on  by David Saliba        

    


    
    

                

                        
php -i | grep -i memcache


Short and sweet

sample output :


memcache

memcache support => enabled

memcache.allow_failover => 1 => 1

memcache.chunk_size => 8192 => 8192

memcache.default_port => 11211 => 11211

memcache.default_timeout_ms => 1000 => 1000

memcache.hash_function => crc32 => crc32

memcache.hash_strategy => standard => standard

memcache.max_failover_attempts => 20 => 20

memcached

memcached support => enabled

libmemcached version => 0.50

Registered save handlers => files user memcache memcached


Njoy 🙂

        

        


	






    


        
		
Using Expect to automate an scp filetransfer

        

            Posted on  by David Saliba        

    


    
    

                

                        
Sometimes you know passwords but are not ion a position to use shared keys. Solution is using expect to pass the password from a script read or a comman line parameter.


** NOTE Passwords in command lines are a really bad idea since you can see them in the history / ps -ef so best is to read from stdio and pass as a parameter.


 


 


#!/usr/bin/expect
spawn scp [lindex $argv 0] root@192.168.8.117:/vmfs/volumes/datastore1/
######################
expect {
-re "Password:" {
exp_send "[lindex $argv 1]\r"
}
}
interact





        

        


	






    


        
		
ESXi 5.1 : Fixing ‘Failed to deploy OVF package: The task was canceled by a user.

        

            Posted on  by David Saliba        

    


    
    

                

                        
Where I work, we love using OVA templates to speed up our deployment of virtual machines. I recently upgraded one of my servers to ESXi 5.1 (which also required an update to vSphere). ESXi 5.1 provides support for Windows 8 and Server 2012, which is incredibly useful. However, whilst building OVA templates for these operating systems, I stumbled across an issue.


I ran through the ‘New Virtual Machine’ wizard, selecting Windows 8 (or Server 2012), leaving all settings default. Installed my operating system, and made the required customisations, shutdown the machine and exported an OVA template through vSphere – excellent, how easy!


However, whilst trying to re-deploy the OVA to the ESXi 5.1 host, through the ‘Deploy OVA template’ wizard, it failed immediately after completing the wizard (right before it shows the deployment progress bar). Now, I have a particular hate for misleading error messages, and this one seems to fall right in-to that category –


Failed to deploy OVF package: The task was canceled by a user.


How misleading. I, or any other user, certainly didn’t cancel the task. So what happened? I took a look through the (horrendous) hostd.log on the ESXi box and found absolutely nothing of any value.


Frustrated by the inability to redeploy a template I spent so long preparing, I broke open the OVA template and took a look inside. There were three files with different extensions,


    

  • .ova – OVF descriptor, written in XML, which describes the hardware requirements
    • 

  • .mf – contains SHA1 checksums of the .OVA and .VMDK
    • 

  • .vmdk – the virtual hard disk for the virtual machine.
    • 



I immediately discarded (renaming to .mfx will do the trick) the .mf. If you modify the .ova and don’t update the .mf, it’ll complain that the checksum is invalid. Removing this file seems to prevent vSphere from checking the checksums, which is useful, seeing as we want to poke around the .ova. After fiddling around inside the .ova, I stumbled across the following line…




<rasd:ResourceSubType>vmware.cdrom.iso</rasd:ResourceSubType>


Changing the above line, to read…


<rasd:ResourceSubType>vmware.cdrom.atapi</rasd:ResourceSubType>


…appears to have fixed my deployment issues. Perhaps changing the ‘CD Drive Device type’ in the virtual machine’s settings would’ve fixed it. But by that point, I had already exported the OVA and deleted the source virtual machine.


Hopefully someone will stumble across this one day, and it’ll save them a few hours!