postgresql FATAL: database system identifier differs between the primary and standby

This is due to two possible reasons:

  1. you did not do the initial filesystem sync (usually rsync)
  2. the recovery.conf contains errors

this page actually helped me

Hope this helps

ISP: ERROR Shibboleth.SSO.SAML2 [xx]: failed to decrypt assertion: XMLSecurity exception while decrypting: OpenSSL:SymmetricKey::decryptFinish – Out of range padding value in final block

The Sp (service provider) replaced the SSL certificate and the metadata used from the Idp are not up-to-date with the public key of the ISP.

This instead is the error message on MS ADFS:

Apache 2.4 mod ldap authnz_ldap debian squeeze closed (connection lost)

It does not work out of the box.

You need to open and edit


and add:

# TLS certificates (needed for GnuTLS)
TLS_CACERT /etc/ssl/certs/ca-certificates.crt

Let me know if this helped.

Docker cheat-sheet

Docker is great for development, but also, it gives you the superpower of extremely small images to easily move around docker containers.

I need this for personal stuff, but I think it can be useful to others, so let’s share it.

It’s a living list so I’m gonna add here stuff as soon as I need it.

Foreplay (Composer) – a.k.a. Install fest
#Install composer:
sudo apt-get -y install python-pip
sudo pip install docker-compose
#Build an image from a dockerfile in pwd:
docker build --rm=true -t tagname .
#--rm=true -> Remove intermediate containers after a successful build
#-t, --tag=[] -> Name and optionally a tag in the 'name:tag' format
#-f, --file -> Name of the Dockerfile (Default is 'PATH/Dockerfile')
Docker Composer
#Start a container with:
docker-compose up -d
#up -> Create and start containers
#-d -> Detached mode: Run containers in the background,
       print new container names.
       Incompatible with --abort-on-container-exit.
#Check what's running:
docker ps

#Stop container:
docker stop {containerid}



Letsencrypt is broken on Debian Jessie

You need backports,

so first add the jessie-backports to your favourite apt source.list

# Backport
deb jessie-backports main

Then apt-get update, and then install back letsencrypt forcing the use of the backports:

apt-get install -t jessie-backports letsencrypt

That’s it,


Unable to configure permitted SSL ciphers SSL Library Error: 336486680 error:140E6118:SSL routines:SSL_CIPHER_PROCESS_RULESTR:invalid command

You copy/pasted the virtualhost configuration from an output that truncated the long line that starts by



Am I right?


Extend Xen guest partition on a live system


No restart of the guest VM is required

on Dom0:

lvextend /dev/lvm/domU.lan-var -L +5G
Extending logical volumedomU.lan-var  to 7.00 GiB
Logical volume successfully resized

On DomU

resize2fs /dev/xvdaX #(where X is a number)
resize2fs 1.42.5 (29-Jul-2012)
Filesystem at /dev/xvdaX is mounted on /var; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/xvdaX to 1835008 (4k) blocks.
The filesystem on /dev/xvdaX is now 1835008 blocks long.



Generate, check, debug and convert with OpenSSL

General OpenSSL Commands

These commands allow you to generate CSRs, Certificates, Private Keys and do other miscellaneous tasks.

  • Generate a new private key and Certificate Signing Request
    openssl req -out CSR.csr -new -newkey rsa:2048 -nodes -keyout privateKey.key
  • Generate a self-signed certificate
    openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout privateKey.key -out certificate.crt
  • Generate a certificate signing request (CSR) for an existing private key
    openssl req -out CSR.csr -key privateKey.key -new
  • Generate a CSR and key for a SAN sertificateCreate a config file called req.cnf to use it with openssl like the following:
  • [req] 
    distinguished_name = req_distinguished_name 
    req_extensions = v3_req 
    prompt = no 
    C = NL 
    ST = NL 
    L = Amsterdam 
    O = Red Light District B.V. 
    OU = IT 
    CN = 
    keyUsage = keyEncipherment, dataEncipherment 
    extendedKeyUsage = serverAuth 
    subjectAltName = @alt_names 
    DNS.1 = 
    DNS.2 = 
    DNS.3 =

With this file use the following command:

openssl req -new -out -newkey rsa:2048 -nodes -sha256 -keyout redlightsdistrict.nlkey.temp -config req.cnf
  • Generate a certificate signing request based on an existing certificate
    openssl x509 -x509toreq -in certificate.crt -out CSR.csr -signkey privateKey.key
  • Remove a passphrase from a private key
    openssl rsa -in privateKey.pem -out newPrivateKey.pem

Checking Using OpenSSL

If you need to check the information within a Certificate, CSR or Private Key, use these commands.

  • Check a Certificate Signing Request (CSR)
    openssl req -text -noout -verify -in CSR.csr
  • Check a private key
    openssl rsa -in privateKey.key -check
  • Check a certificate
    openssl x509 -in certificate.crt -text -noout
  • Check a PKCS#12 file (.pfx or .p12)
    openssl pkcs12 -info -in keyStore.p12
  • Check a CA bundle against a certificate
    openssl verify -verbose -purpose sslserver -CAfile <chain file> <cert>
    • Check certificate issuer
openssl x509 -noout -in cert.pem -issuer
    • Check the subject for whom the cert has been issued
openssl x509 -noout -in cert.pem -subject
    • Check validity (dates)
openssl x509 -noout -in cert.pem -dates
    • Check the above 3, all at once
openssl x509 -noout -in cert.pem -issuer -subject -dates
    • Check hash value
 openssl x509 -noout -in cert.pem -hash
    • Check certificate MD5 fingerprint
openssl x509 -noout -in cert.pem -fingerprint

Check an MD5 hash of the public key to ensure that it matches with what is in a CSR or private key

openssl x509 -noout -modulus -in certificate.crt | openssl md5
openssl rsa -noout -modulus -in privateKey.key | openssl md5
openssl req -noout -modulus -in CSR.csr | openssl md5


Debugging Using OpenSSL

If you are receiving an error that the private doesn’t match the certificate or that a certificate that you installed to a site is not trusted, try one of these commands.

  • Check an MD5 hash of the public key to ensure that it matches with what is in a CSR or private key
    openssl x509 -noout -modulus -in certificate.crt | openssl md5
    openssl rsa -noout -modulus -in privateKey.key | openssl md5
    openssl req -noout -modulus -in CSR.csr | openssl md5
  • Check an SSL connection. All the certificates (including Intermediates) should be displayed
    openssl s_client -connect
  • If the dns hasn’t propagated yet you can use an ip address and a hostname like the following example
$ openssl s_client -connect -servername

Converting Using OpenSSL

These commands allow you to convert certificates and keys to different formats to make them compatible with specific types of servers or software. For example, you can convert a normal PEM file that would work with Apache to a PFX (PKCS#12) file and use it with Tomcat or IIS.

  • Convert a DER file (.crt .cer .der) to PEM
    openssl x509 -inform der -in certificate.cer -out certificate.pem
  • Convert a PEM file to DER
    openssl x509 -outform der -in certificate.pem -out certificate.der
  • Convert a PKCS#12 file (.pfx .p12) containing a private key and certificates to PEM
    openssl pkcs12 -in keyStore.pfx -out keyStore.pem -nodes

    You can add -nocerts to only output the private key or add -nokeys to only output the certificates.

  • Convert a PEM certificate file and a private key to PKCS#12 (.pfx .p12)
    openssl pkcs12 -export -out certificate.pfx -inkey privateKey.key -in certificate.crt -certfile CACert.crt
  • Convert a p7b (non binary) certificate to Pem
    openssl pkcs7 -in certificate_file.p7b -print_certs -out cert.pem

    If this throws an error, just open the p7b fiel and replace:

    -----BEGIN PKCS #7 SIGNED DATA-----
    -----END PKCS #7 SIGNED DATA-----


    -----END CERTIFICATE-----
    • Convert a p7b (binary) certificate to Pem

      You can easily guess whether a certificate is in a binary form by looking at it with for instance the cat command, If it looks garbled it’s binary
      In these cases you should first convert it from binary tand then you can convert it to pem with the previous example. This is how you convert it if binary:

      openssl pkcs7 -inform der -in a.p7b -out a.cer
    • SSL bundle concatenation order for haproxy:


Originally posted on Sun Jan 13, 2008 at expanded, enriched and improved with personal experiences since then.