Apple and BlackBerry email clients has a configurable setting to use the IMAP IDLE functionality to stay logged in, periodically checking email. This causes imapd to run out of daemons and stop responding. One solution is to raise MAXDAEMONS in /etc/courier-imap/imapd, but will eventually cause high loads on the server.

The better solution is to disable IDLE entirely in /etc/courier-imap/imapd by removing "IDLE" option from "IMAP_CAPABILITY".

Change:

To:

Upon courier-imap restart, this should prevent connections from persisting.

Telnet to imap port 143 to verify that the IDLE option is not present anymore in CAPABILITY response from the server.

Use qmail-qstat or qmail-qread to check the messages in queue.

Run qmail-tcpok to clear out the TCP timeout table.

After that, send the "ALRM " signal to the "qmail-send" process, and Qmail will process all messages in the queue immediately:

Below script checks and kills any sql SELECT statements that has been running for more than 60 seconds. The script can be added to a cron task to be run periodically. Make sure to check the log file it creates to keep an eye on the long running sql statements and tune it.

Prior to running it, setup the root login in "~/.my.cnf" file with the login credentials:

When developers shift from PHP, Ruby or any other platform to Python, the very first road block they face (most often) is a lack of an overall understanding of the Python ecosystem. Developers often yearn for a tutorial or resource that explains how to accomplish most tasks in a more or less standard way.

What follows is an extract from the internal wiki at my workplace, which documents the basics of the Python ecosystem for web application development for our interns, trainees and experienced developers who shift to Python from other platforms.

You can easily install ImageMagick and PHP imagick extension from remi repository. There are some dependencies from epel repository too.

• dnsmasq-base has to be installed:
  sudo apt-get install dnsmasq-base

• Remove dnsmasq because it conflicts with NetworkManager:
  sudo apt-get remove dnsmasq

• Restart NetworkManager:
  sudo /etc/init.d/network-manager restart

• Add a new wireless network with NetworkManager (left-click on NetworkManager icon, then select "Create New Wireless Network").
  
• Set encryption to WEP 40/128-bit Key with a 13 characters key. (Note: You may have to experiment here according to what type of encryption with ad-hoc the device supports. WPA is not supported).
  
• NetworkManager now should connect to itself (which means it creates the ad-hoc wireless network and routes any Internet traffic to your wired network interface). Now, connect with the client(s), and you should have a working Internet connection.
  
• You have to make sure that this connection is shared to other computers and devices (clients). Make sure that the Connect automatically check-box is selected and on the IPv4 Settings tab make sure that the Method option is set to "Shared to other computers".

While updating vzctl to latest on CentOS-5.8, I was getting the below error:

Turns out that ploop is no longer required for vzctl on CentOS-5.8 and can be removed:

yum update problem on CentOS 5.8 server

"Since you have RHEL5-based kernel that do not require ploop, you can remove ploop when installing vzctl-4.0. I have made vzctl not requiring ploop by dynamically loading it when it's available. Note that vzctl is not requiring ploop anymore, it just conflicts with the old version of it."

The solution was to remove ploop in single transaction as mentioned:

So, you have a binlog. You want to find out something specific that happened inside of it. What to do? mysqlbinlog has some neat features, which I thought we would look at here.

I should first explain what mysqlbinlog really is. It is a tool that lets you analyze and view the binlogs/relaylogs from mysql, which are stored in binary format. This tool converts them to plaintext, so that they’re human-readable.

iscsi target

• Install iscsi utils:
  
  yum install scsi-target-utils
• Bring up tgtd:
  
  chkconfig tgtd on
service tgtd start
• Define an iscsi target name:
  
  # tgtadm --lld iscsi --op new --mode target --tid 1 -T iqn.2012-10.com.linuxweblog.srv01:lv1_iscsi0
• Delete specific iscsi target:
  
  # tgtadm --lld iscsi --op delete --mode target --tid 1
• Add a logical unit to the target:
  
  # tgtadm --lld iscsi --op new --mode logicalunit --tid 1 --lun 1 -b /dev/vg1/lv1_iscsi0
• Delete logical unit:
  
  # tgtadm --lld iscsi --op delete --mode logicalunit --tid 1 --lun 1
• Enable the target to accept any initiators:
  
  # tgtadm --lld iscsi --op bind --mode target --tid 1 -I ALL
• View configuration:
  
  # tgtadm --lld iscsi --op show --mode target
• Save the tgt conf:
  
  # tgt-admin --dump >/etc/tgt/targets.conf

iscsi initiator

• install the initiator client:
  
  # yum install iscsi-initiator-utils
• startup the iscsi daemon so all kernel modules get loaded:
  
  # chkconfig iscsid on
# chkconfig iscsi on
# service iscsid start
• Discover targets:
  
  # iscsiadm --mode discovery --type sendtargets --portal 192.168.1.11
• Login to target:
  
  # service iscsi restart
• To manually login:
  
  # iscsiadm --mode node --targetname iqn.2012-10.com.linuxweblog.srv01:lv1_iscsi0 --portal 192.168.1.11 --login
• To manually logout:
  
  # iscsiadm --mode node --targetname iqn.2012-10.com.linuxweblog.srv01:lv1_iscsi0 --portal 192.168.1.11 --logout
• To delete targets:
  
  # iscsiadm --mode node --targetname iqn.2012-10.com.linuxweblog.srv01:lv1_iscsi0 --portal 192.168.1.11 -o delete
• List sessions:
  
  # iscsiadm -m session
• List nodes:
  
  # iscsiadm -m node

Create a "config" file in your "~/.ssh" directory with the below contents:

The key is to set CheckHostIP to "no" and use "HostKeyAlias" to specify an alias that should be used instead of the real host name when looking up or saving the host key in the host key database files.

The Port line avoids having to specify the port when connectig.

Connect to corresponding host via: