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• munin-node installed via epel repository.
  
• Install perl-Cache-Cache:
  
  # yum install munin-node perl-Cache-Cache
• Create file "/etc/munin/plugin-conf.d/mysql" with below contents:
  
  [mysql*]
env.mysqluser munin
env.mysqlpassword {PASS}
• Create mysql user and assign corresponding privileges:
  
  mysql> create user munin@localhost identified by '{PASS}';
mysql> GRANT PROCESS, SUPER ON *.* TO 'munin'@'localhost';
mysql> GRANT SELECT ON `mysql`.* TO 'munin'@'localhost';
mysql> flush privileges
• Check the suggestions and install the plugins:
  
  munin-node-configure  --suggest 2>/dev/null |grep mysql
munin-node-configure  --shell | grep mysql | sh
• Test via:
  
  # cd /etc/munin/plugins
# munin-run mysql_connections

Java is a programming language and computing platform first released by Sun Microsystems in 1995. It is the underlying technology that powers state-of-the-art programs including utilities, games, and business applications. Java runs on more than 850 million personal computers worldwide, and on billions of devices worldwide, including mobile and TV devices.

After Plesk upgrade to 9.5.4, imapd on port 143 did not come up.

On checking the maillog, it was complaining about:

I noticed /etc/courier-imap/imapd had both the below lines commented:

Once I uncommented those values, I was able to get the imap listener up upon a `service courier-imap restart`.

Recently, I've had to move a postgresql database onto a separate server and split it out from the django application server.

On doing so, we saw intermittent "OperationalError: could not connect to server: Connection timed out".

This was quite obvious that the "connect_timeout" had to be increased to resolve the issue due to the latency introduced by the network. However, psycopg2 database adapter was being used which did not support the "connect_timeout" option to be passed via django.

We were able to work around the issue setting the environmental variable "PGCONNECT_TIMEOUT" so libpq would pick up the connection parameter.

Put the below in "django.wsgi":

While setting up munin to monitor postgresql, I was getting "[DBD::Pg not found, and cannot do psql yet]" when running `munin-node-configure --suggest | grep postgres`.

I confirmed that the rpm package "perl-DBI-1.52-2.el5" was indeed installed.

However, when I ran a test against the module, it failed with:

On checking the library, it returned with "libpq.so.4 => not found":

Indeed libpq.so.4 was missing since postgresql90-libs was installed which only includes "libpq.so.5".

To get libpq.so.4, "compat-postgresql-libs" package needed to be installed.

Once installed the perl module test passed and I was able to get the munin plugins linked using:

RNDC is a useful mechanism for administering DNS servers. If it is not configured, BIND complains about it.

Determine the locations where RNDC expects to find the config files.

Create the rndc config file:

Thy rndc conf file should also have the contents that need to go to "/etc/named.conf". See sample below:

Once the key and control section has been added to named.conf, restart named and test again with:

The stub_status module provides the ability to get some stats from nginx...

active connections -- number of all open connections including connections to backends

server accepts handled requests -- nginx accepted connections, handled connections (no one was closed just it was accepted), and handles requests (requests per connection = handles requests / handled connections)

reading -- nginx reads request header

writing -- nginx reads request body, processes request, or writes response to a client

waiting -- keep-alive connections, actually it is (active - reading + writing)

When using tmpfs inside OpenVZ containers, make sure to monitor and increase dcachesize (directory and inode entries) appropriately.

tmpfs mounts can be used to speed up applications doing lots of read/writes to temporary diskspace such a php sessions and mysql tmp directory.

Mount using "/etc/fstab":

Note: default folder permission of "/var/lib/php/session" is 770 and set to the apache Group ID.

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Whenever sendmail has to deliver mails to other hosts which cannot be reached at that time, the messages are kept in the queue. Although the other hosts could be reached again and you want to tell sendmail to flush the mail queue, the command

sendmail -q -v

does not really try to reconnect to these hosts and still assumes that the connection timed out. The reason is that the hoststatus is cached, per default for a period of 30 minutes. Using

sendmail -OTimeout.hoststatus=0m -q -v

you can re-run the mail queue and force sendmail to reconnect to the hosts.