Category: Linux
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Brief Introduction to Zimbra Internal Architecture
In some cases, you might want to recover your data from Zimbra, or you may be curious about how Zimbra manages users and emails behind the scenes. I dug into Zimbra’s nuts and bolts because we lost Zimbra’s local LDAP, which took more than 3 days to fix, so I wanted to share what I…
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SSH Access Without OS Shell in Gitlab
Exposing SSH of your gitlab on the internet could be dangerous as attackers can get shell access into your server. So here we show you a way to enable SSH for Git without opening access to shell of the hosting OS. Step 1: Run another SSH instance just for gitlab Copy sshd config file and…
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Provisioning DNS Server Using PowerDNS
When you want to setup a DNS server on *nix platform, the first option that may cross your mind is bind9. But there are other options such as PowerDNS. In this post I’m going to show you how to setup a DNS server in single node mode. This DNS server is going to be authoritative…
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Using Putty to Automate Cisco Devices
Sometimes you want to automate some cumbersome tasks in your Cisco devices, namely I am dealing with an old 3750 core router with OS version 12.x and I don’t want to login to it manually every time I want to change a config or shutdown an interface. Hence I thought I can make use of…
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How to Create JWT Token Using LDAP and Spring Boot Part 1
If you are working in an enterprise infrastructures, chances are that you are using a centralized authentication system, most likely Active Directory or openLDAP. In this blog I’ll explore how to create a REST API using spring boot to authenticate against openLDAP and create a JWT token in return. Before getting our hand dirty, we…
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How to Authenticate Against openLDAP Without Knowing DN Using java
In fact you can’t do it without knowing DN! There is an anonymous access in openLDAP which is enabled by default. The anonymous access let one to query(search filter) openLDAP without knowing bind username/password. Run following command on your openLDAP server : ldapwhoami -H ldap:// -x If you get “anonymous” as result you are all…
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Installing openLDAP and Making it Replicable
OpenLDAP installation is fairly straight-forward and doesn’t have any caveats, but making it replicable has ambiguity. We will start with installing openLDAP. I will use following configs : ubuntu 16.04 server openLDAP 2.4.x phpLDAPadmin Installing openLDAP : First thing first, update your ubuntu box : sudo apt-get update Install openLDAP : sudo apt-get install slapd…
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How to Configure Iptables in Stateful Mode Properly
Iptables is a software firewall based on Netfilter, in fact it’s a framework for working with Netfilter. Generally firewalls have two modes, stateless and stateful. In this post we will study a brief of how to configure Netfilter in stateful mode. I’m going to assume your linux box is fresh installation and doesn’t have any…
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Enabling LDAP on Linux and local user’s session will interchange with LDAP’s user intermittently
Let’s say you have a central authentication server in a LDAP and you successfully connect your Linux box as a client to LDAP server. Whenever you are using a particular LDAP user to login to your box, your shell get confused and change the LDAP user with a local user of your box intermittently. What is…
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After configuring Ubuntu to use LDAP ssh login become too slow
This is a common symptom of mis behaviour of systemd-logind. I couldn’t still find-out what is really happening underneath of this service but if you experience such issues you can try to restart the service using following command sudo service systemd-logind restart and make sure to run this code on the console not just by…