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Linux Screen Shortcuts

August 18, 2011 mohancheema 0

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
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Apache connections dropped by Haproxy

October 6, 2010 mohancheema 0

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

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ip_conntrack_max table full dropping packets

September 28, 2010 mohancheema 0

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:

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How to get MySQL table Column Names without MetaData

September 1, 2010 mohancheema 0

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.

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Clearing the cache from memory

August 18, 2010 mohancheema 0

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.