1. Telnet to postfix mail server using TCP port 25.
Command is telnet <servername/serverip> 25
response should be as follows
220 ********************************************
How to test Postfix SMTP using Telnet
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Category Archives: Tips
Linux Screen Shortcuts
Screen is a much under utilised program, which provides the following functionality:
- Remote terminal session management (detaching or sharing terminal sessions)
- unlimited windows (unlike the hard-coded number of Linux virtual consoles)
- Scroll back buffer (not limited to video memory like Linux virtual consoles)
- copy/paste between windows
Forgot the root password of your linux box
So you forgot your root password of your linux box?, well its not the end of the world if you do have physical / KVM over IP access to your box, you can start it on single user mode and reset it. Don’t know how?… then read on.
Explaining Server Load
Introduction:
To explain what server loads really are and how to control them, how to watch loads and signs of server trouble.
Apache connections dropped by Haproxy
Many times on RHEL, haproxy is not reliable it gives an errors while connecting to apache backend, at that time it logs the following errors into /var/log/messages
kernel: ip_conntrack: table full, dropping packet
this is related to ip_conntrack kernel module.
If found this error message into /var/log/messages need to apply following steps
ip_conntrack_max table full dropping packets
If you notice the above message in syslog, it looks like the conntrack database doesn’t have enough entries for your environment. Connection tracking by default handles up to a certain number of simultaneous connections. This number is dependent on you system’s maximum memory size.
Some symptoms can be:
How to get MySQL table Column Names without MetaData
Often we need to list just the column name of the table without displaying the metadata. However, Until before MySQL 5.0 there was no way to get just the column names for any given table. Since MySQL 5.0 new table has been added information_schema. INFORMATION_SCHEMA provides access to database metadata.
Clearing the cache from memory
Linux has a supposedly good memory management feature that will use up any “extra” RAM you have to cache stuff. This section of the memory being used is supposed to be freely available to be taken over by any other process that actually needs it, but unfortunately some Linux distros think that cache memory is too important to move over for anything else that actually needs it.
vsftpd: Error 553 – Could not create file OR login error 530
It often happens when we install vsftpd on newly installed system and configure it properly still sometimes we get one of the following error.
- vsftpd: Error 553 – Could not create file
- vsftpd: Error 530 – Login Incorrect (Even if username and password are correct)
Solaris Recursive GREP
Linux shells provide a recursive Grep function in the form of the -r switch.
However, in Solaris this function have to be replicated using the piped command as follows:
find . | xargs grep ‘pattern’
Or if your shell doesn’t has all the right paths set, then: