FirstServed Tech Blog - FirstServed and the Art of Server Tuning

Extracting language strings from PHP is best done woth xgettext… in order you are using the _(”) function to specify your text fragments.

Afterwards on the server you must run the following command to create a translatable *.po file which then can be eidtied using programs like poEdit:

Hi,

A quick guide on how to create selfsigned certificates using openssl:

Setup Ca environment:

vi /etc/pki/tls/openssl.cnf

dir             = /usr/local/lib/CA     # Where everything is kept

cd /usr/local/lib
mkdir CA
mkdir newcerts private
echo '01' > serial
touch index.txt

cd /usr/local/lib/CA

Generate key:

openssl genrsa -des3 -out server.key 1024

Generating RSA private key, 1024 bit long modulus

......................................++++++

................................................++++++

e is 65537 (0x10001)

Enter pass phrase for server.key:

Verifying - Enter pass phrase for server.key:

Generate self signed root certificate:

openssl req -new -x509 -days 3560 -key server.key -out server.crt

Enter pass phrase for server.key:

You are about to be asked to enter information that will be incorporated

into your certificate request.

What you are about to enter is what is called a Distinguished Name or a DN.

There are quite a few fields but you can leave some blank

For some fields there will be a default value,

If you enter '.', the field will be left blank.

-----

Country Name (2 letter code) [GB]:BE

State or Province Name (full name) [Berkshire]:Antwerpen

Locality Name (eg, city) [Newbury]:Berchem

Organization Name (eg, company) [My Company Ltd]:FirstServed NV/SA

Organizational Unit Name (eg, section) []:

Common Name (eg, your name or your server's hostname) []:ca.firstserved.net

Email Address []:nospam@firstserved.net

Create client key:

openssl genrsa -out quorumd.key 1024

Generating RSA private key, 1024 bit long modulus

............++++++

.........................................................++++++

e is 65537 (0x10001)

Create the certificate request for the client:

openssl req -new -days 3560 -key quorumd.key -out quorumd.csr

You are about to be asked to enter information that will be incorporated

into your certificate request.

What you are about to enter is what is called a Distinguished Name or a DN.

There are quite a few fields but you can leave some blank

For some fields there will be a default value,

If you enter '.', the field will be left blank.

-----

Country Name (2 letter code) [GB]:BE

State or Province Name (full name) [Berkshire]:Antwerpen

Locality Name (eg, city) [Newbury]:Berchem

Organization Name (eg, company) [My Company Ltd]:FirstServed NV/SA

Organizational Unit Name (eg, section) []:

Common Name (eg, your name or your server's hostname) []:bemobile

Email Address []:nospam@firstserved.net

Please enter the following 'extra' attributes

to be sent with your certificate request

A challenge password []:

An optional company name []:

Sign the request using your self-signed certificate:

openssl ca -days 3560 -in quorumd.csr -cert server.crt -keyfile server.key -out quorumd.crt

Using configuration from /etc/pki/tls/openssl.cnf

Enter pass phrase for server.key:

Check that the request matches the signature

Signature ok

Certificate Details:

        Serial Number: 1 (0x1)

        Validity

            Not Before: May 22 10:44:49 2008 GMT

            Not After : Feb 19 10:44:49 2018 GMT

        Subject:

            countryName               = BE

            stateOrProvinceName       = Antwerpen

            organizationName          = FirstServed NV/SA

            commonName                = bemobile

            emailAddress              = nospam@firstserved.net

        X509v3 extensions:

            X509v3 Basic Constraints:

                CA:FALSE

            Netscape Comment:

                OpenSSL Generated Certificate

            X509v3 Subject Key Identifier:

                29:A5:E4:6A:F4:4E:89:35:5D:7D:C6:9A:CE:B9:D0:1B:75:0A:7F:8C

            X509v3 Authority Key Identifier:

                keyid:4B:B2:BA:F6:65:66:60:EB:CC:45:F5:57:34:FB:E9:AB:40:CF:B4:E8

Certificate is to be certified until Feb 19 10:44:49 2018 GMT (3560 days)

Sign the certificate? [y/n]:y

1 out of 1 certificate requests certified, commit? [y/n]y

Write out database with 1 new entries

Data Base Updated

That should do it.

Koen

Hi,

After tweaking your storage repositories you might want to change the value for the default SR.
This can be done using the following command:
xe pool-param-set uuid=1ad826b1-9c9f-fd8a-3a50-b8ce3a0841af default-SR=8312500f-9962-59ff-9b0e-797987963750

Don’t forget to change the uuids to the ones that match your configuration!

Koen

Hi,

After being able to mirror the data of my guests using a DRBD setup between 2 servers, I obviously wanted to copy the config of these guest machines to.
(Otherwise the data mirror would be rather useless.)
But since I did already have all the data perfectly in sync, I did not want to do a complete export of the virtual machine.
I found an option which allows you to backup only the configuration (metadata) of a guest machine. This way you are free to setup your own data mirrorring solution.
The command:
[root@snake ~]# xe vm-export vm=12c2ee4d-16fd-5564-0589-9f302e4aa329 filename=/root/ddk –metadata

To import the data, just copy the file (here /root/ddk) over to your other server and use the following command to import your guest:
[root@jeremy ~]# xe vm-import filename=/root/ddk –metadata
You might need to manually specify the SR, in which case the command becomes:
xe vm-import filename=/root/ddk sr-uuid=8312500f-9962-59ff-9b0e-797987963750 –metadata

(Please note that wordpress doesn’t like the 2 hyphens before the word metadata and displays only one, the option is "- -metadata" without the space between those 2 hyphens.)

Don’t you just love these undocumented switches?

Koen

Hi,

Using DRBD on Xenserver is fairly simple.
Just download the Driver Development kit from Citrix for XenServer 4.1.
Import the DDK to your server.
Download your DRBD release (source code) of choice (we used version 8.2.5).
Put it inside the DDK, extract, run the magical command "make rpm" and off you go!

The packages will be ready soon. Just SCP them out of your DDK to any Xenserver you want to install them on.
No additional dependencies are needed to be resolved.

BEWARE: Citrix doesn’t support custom modules (and most likely they won’t ever support DRBD).

Kind Regards,

Koen

Hi,

In this entry I will try to explain how to create one storage repository on a device used by two Xenservers.
Such a setup may be archieved by using DRBD in a primary-primary state between the Xenservers.
The Xenserver version used for this entry is: 4.1.0

First of all, create some room, this can be done by removing your old repository.
www.firstserved.net/blog/2008/05/08/how-to-remove-a-storage-repository/

On your primary server, this command should cover about everything (PBD + SR creation):
xe sr-create name-label=SR-DRBD0 type=lvm shared=false device-config:device=/dev/drbd0

The secondary server however needs some more care:
As you can see with the command "vgdisplay", the command on the primary server has already created a volume group for the data:
[root@jeremy ~]# vgdisplay
  — Volume group —
  VG Name               VG_XenStorage-8312500f-9962-59ff-9b0e-797987963750
  System ID
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  1
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                0
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               258.15 GB
  PE Size               4.00 MB
  Total PE              66087
  Alloc PE / Size       0 / 0
  Free  PE / Size       66087 / 258.15 GB
  VG UUID               0bdET3-DGv5-KSX2-4rag-vgDA-ClmD-Flq9pX

We can’t just delete this because that would break our primary server.

So we introduce the new storage repository on our secondary server instead of creating a new one using the same parameters and uuid as our primary server:
xe sr-introduce name-label=SR-DRBD0 uuid=8312500f-9962-59ff-9b0e-797987963750 shared=false type=lvm

When we now ask a listing of the Storage Repositories, we get this new entry:
uuid ( RO)                : 8312500f-9962-59ff-9b0e-797987963750
          name-label ( RW): SR-DRBD0
    name-description ( RW):
                host ( RO): <not in database>
                type ( RO): lvm
        content-type ( RO): disks
As you can see, some data is still missing.
This data will be filled up after creating the PBD.
(The command xe sr-introduce doesn’t create a PBD for the introduced SR.)
For the creation of a PBD, you will need the hosts uuid, which can be found using:
[root@jeremy ~]# xe host-list
uuid ( RO)                : 38e2b381-697d-4a11-971d-53ed1dcecd72
          name-label ( RW): jeremy.firstserved.net
    name-description ( RO): Default install of XenServer

Now we are ready to create the PBD:
xe pbd-create host-uuid=38e2b381-697d-4a11-971d-53ed1dcecd72 sr-uuid=8312500f-9962-59ff-9b0e-797987963750 device-config:device=/dev/drbd0

Now we can see the new PBD in the listing:
[root@jeremy ~]# xe pbd-list
uuid ( RO)                  : 19f7f1df-7679-bd59-604e-37110e72ad3f
             host-uuid ( RO): 38e2b381-697d-4a11-971d-53ed1dcecd72
               sr-uuid ( RO): 8312500f-9962-59ff-9b0e-797987963750
         device-config (MRO): device: /dev/drbd0
    currently-attached ( RO): false

The last action to do is to attach the PBD to the system:
xe pbd-plug uuid=19f7f1df-7679-bd59-604e-37110e72ad3f

And you should be ready to go!

Koen

Hi,

This entry describes how to remove a Xen storage repository from a XenServer 4.1 Server.
Removal of a Storage repository may be needed after damage to the disk has occured or when organising one or more xen servers in a custom setup.

When trying to remove a SR, you might encounter nasty error messages like:
[root@jeremy ~]# xe pbd-destroy uuid=4c057786-4fd3-eefa-c098-39a2e9eabbf2
You attempted an operation that was not allowed.
reason: PBD is currently attached
[root@jeremy ~]# xe sr-forget uuid=d22f5ac3-4f8d-cb7c-85ed-eb32288d8371
The SR is still connected to a host via a PBD. It cannot be destroyed.
sr: d22f5ac3-4f8d-cb7c-85ed-eb32288d8371 (Local storage)

So here is a small explanation on how to really remove your repository.
First of all, find the uuid of your Storage repositiry using  "xe sr-list"
uuid ( RO)                : e98c3da7-14f7-c2ae-3a15-c50965244cc9
          name-label ( RW): storage
    name-description ( RW):
                host ( RO): jeremy.firstserved.net
                type ( RO): lvm
        content-type ( RO): disk

Now search the corresponding PBD entry using "xe pbd-list":
uuid ( RO)                  : 4c057786-4fd3-eefa-c098-39a2e9eabbf2
             host-uuid ( RO): 38e2b381-697d-4a11-971d-53ed1dcecd72
               sr-uuid ( RO): e98c3da7-14f7-c2ae-3a15-c50965244cc9
         device-config (MRO): device: /dev/drbd0
    currently-attached ( RO): true

As you can see, the SR (Storage Repository) can easily be tracked using the uuid.

Now unplug the PBD from the SR:
xe pbd-unplug uuid=4c057786-4fd3-eefa-c098-39a2e9eabbf2

This allows you to either forget or destroy the SR:
xe sr-destroy uuid=e98c3da7-14f7-c2ae-3a15-c50965244cc9

As you can see, the storage repository has been removed from the system:
[root@jeremy ~]# xe sr-list
uuid ( RO)                : b7060810-f98f-ddfc-2c1a-e829570ed373
          name-label ( RW): Removable storage
    name-description ( RW):
                host ( RO): jeremy.firstserved.net
                type ( RO): udev
        content-type ( RO): disk

uuid ( RO)                : b89f976a-46e3-3e88-febd-685d624cffa3
          name-label ( RW): XenServer Tools
    name-description ( RW): XenServer Tools ISOs
                host ( RO): jeremy.firstserved.net
                type ( RO): iso
        content-type ( RO): iso

uuid ( RO)                : 861138a5-f359-74a7-93f1-c20fbdb1c8a0
          name-label ( RW): DVD drives
    name-description ( RW): Physical DVD drives
                host ( RO): jeremy.firstserved.net
                type ( RO): udev
        content-type ( RO): iso

Greets,

Koen