Quick and dirty fix for VMware Linux guests loosing clock accuracy

I covered on a previous post how to keep the clock synchronized for VMware Linux guest(s). Well this seems to not work at least for recent versions VMware Server 2 (i.e. the one with web based management console). For now the quick& dirty solution I am using is putting a cron job that executes ntpdate pretty often…

My cron job looks like this:

#
# Temporary fix for the time getting lost
#
0-59/10 * * * * /usr/sbin/ntpdate north-america.pool.ntp.org > /dev/null 2>1

Yes, this fix requires to have NTPDATE installed (apt-get install ntpdate under Debian).

How to install MySQL Server on Debian Linux

While installing MySQL Server it is always good to keep in mind that the logs and data folders will potentially have a big size. By default MySQL keeps them in the root mount point (i.e. ‘/’). That may cause your database server system disk to get full, which is never a good idea.

This article describes how to move these two folders to ‘/home’ which is ideally mounted into another disk and has enough space to keep your database data and logs.

First, I install the required apt-get packages as follows:

apt-get update
apt-get install mysql-server

To check the status:

/etc/init.d/mysql status

/usr/bin/mysqladmin  Ver 8.41 Distrib 5.0.51a, for debian-linux-gnu on i486
Copyright (C) 2000-2006 MySQL AB
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license

Server version          5.0.51a-24
Protocol version        10
Connection              Localhost via UNIX socket
UNIX socket             /var/run/mysqld/mysqld.sock
Uptime:                 3 sec

Threads: 1  Questions: 78  Slow queries: 0  Opens: 23  Flush tables: 1
Open tables: 17  Queries per second avg: 26.000.

Now, stop MySQL, move the folders to the right location, reconfigure MySQL and start again:

# Stop MySQL
/etc/init.d/mysql stop

# Move and reconfigure data
mkdir /home/mysql
mv /var/lib/mysql /home/mysql/mysql-data
ln -s /home/mysql/mysql-data/ /var/lib/mysql

# Move and reconfigure logs
mv /var/log/mysql/ /home/mysql/mysql-logs
ln -s /home/mysql/mysql-logs/ /var/log/mysql

# Start MySQL and check that everything is OK
/etc/init.d/mysql start
/etc/init.d/mysql status
/usr/bin/mysqladmin  Ver 8.41 Distrib 5.0.51a, for debian-linux-gnu on i486
Copyright (C) 2000-2006 MySQL AB
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license

Server version          5.0.51a-24
Protocol version        10
Connection              Localhost via UNIX socket
UNIX socket             /var/run/mysqld/mysqld.sock
Uptime:                 14 sec

Threads: 1  Questions: 78  Slow queries: 0  Opens: 23  Flush tables: 1
Open tables: 17  Queries per second avg: 5.571.

These are some settings that I usually put on the /etc/mysql/my.cnf configuration file:

# Here you can see queries with especially long duration
log_slow_queries        = /var/log/mysql/mysql-slow.log
long_query_time         = 1
log-queries-not-using-indexes

# A server-id unique
server-id                = 177
log-bin                  = /var/log/mysql/mysql-bin.log
log-bin-index            = /var/log/mysql/mysql-bin.log
innodb_file_per_table
# Unique log names (this prevents replication breaking upon hostname change :-) 
relay-log                = iamalsounique98127-relay-bin
relay-log-index          = iamalsounique98127-relay-bin

# Taking care of the auto-increment values (for multi-master replication)
auto_increment_increment      = 10
auto_increment_offset         = 1

For these changes to take effect, you would need to restart MySQL:

/etc/init.d/mysql restart

If you want to ignore databases or tables you may use the following options:

binlog_ignore_db        = information_schema
replicate_ignore_db     = information_schema
binlog_ignore_db        = mysql
replicate_ignore_db     = mysql

# Ignore all the cache* tables which have caused DUPLICATE
# ENTRY issues. Unai.
replicate_wild_ignore_table = exampledb.cache%

Having ‘binlog_ignore_db’ is enough to exclude databases from replication BUT having ‘replicate_ignore_db’ as well will make things clearer since the databases that are being ignored will appear in both the ‘SHOW SLAVE STATUSG’ and ‘SHOW MASTER STATUSG’.

KeepAlived Installation under Debian Etch

Briefly, KeepAlived is a daemon that is able to provide failover capabilities to servers/services by binding virtual IP addresses to machines. In the event of failure, KeepAlived would reassign this virtual IP to another machine. This action is executed fast (less than 2 seconds) and automatically.

This is a very interesting daemon to be used in combination with HAProxy, for example. It would be possible to have a failovered load balancer. In the event of this load balancer failing, keepalived would switch to another that is up and running in such a clean and fast way that the clients would not notice.

Installation steps under Debian Etch

apt-get update
apt-get install keepalived

The system will ask a couple of questions. I usually reply using the default values, then configure myself manually the daemon, by editing /etc/keepalived/keepalived.conf.

To make the virtual IP address bindable, you should add this line /etc/sysctl.conf:

net.ipv4.ip_nonlocal_bind=1

Check binding:

sysctl -p

net.ipv4.ip_nonlocal_bind = 1

It is convenient to alter the order when keepalived is being started upon restarts. We probably want to have it started at the end so all the services are already running by the time keepalive runs. To do that:

update-rc.d -f keepalived remove
Removing any system startup links for /etc/init.d/keepalived ...
/etc/rc0.d/K20keepalived
/etc/rc1.d/K20keepalived
/etc/rc2.d/S20keepalived
/etc/rc3.d/S20keepalived
/etc/rc4.d/S20keepalived
/etc/rc5.d/S20keepalived
/etc/rc6.d/K20keepalived

update-rc.d keepalived defaults 90
Adding system startup for /etc/init.d/keepalived ...
/etc/rc0.d/K90keepalived -> ../init.d/keepalived
/etc/rc1.d/K90keepalived -> ../init.d/keepalived
/etc/rc6.d/K90keepalived -> ../init.d/keepalived
/etc/rc2.d/S90keepalived -> ../init.d/keepalived
/etc/rc3.d/S90keepalived -> ../init.d/keepalived
/etc/rc4.d/S90keepalived -> ../init.d/keepalived
/etc/rc5.d/S90keepalived -> ../init.d/keepalived

See Also

How to install NAGIOS NRPE plugin under Debian Linux

NRPE allows you to remotely execute Nagios plugins on other Linux/Unix machines. This allows you to monitor remote machine metrics (disk usage, CPU load, etc.). NRPE can also communicate with some of the Windows agent addons, so you can execute scripts and check metrics on remote Windows machines as well. Citation.

You may follow the steps to install NRPE in any of the following ways:

1) Steps (compiling from sources)

First, you should download the latest NRPE version from HERE.

Then, install some required packages:

apt-get update
apt-get install build-essential libssl-dev

Unpack the NRPE addons, configure and install:

cd /opt
tar xvfz nrpe-2.12.tar.gz
cd nrpe-2.12
./configure --enable-command-args
make all
make install-plugin

2) Steps (using apt binaries)

apt-get update
apt-get install nagios-nrpe-plugin

Invocation
NRPE can now be invoked using the following:

/usr/lib/nagios/plugins/check_nrpe

Another option would be to create a symlink to make the invocation easier:

ln -s /usr/lib/nagios/plugins/check_nrpe /usr/bin/check_nrpe

Thus:

check_nrpe

Fixing VMWare vmxnet driver networking issues under Debian Linux

It seems that using particular combinations of VMWare Server and Linux Kernel version(s) while installing VMWare Tools under Linux guest machines, may render the virtual machine’s networking down.

This page provides a “hacky” workaround to solve this situation. There might be other deeper and more proper solutions out there but I came up with this one because it is very simple to put in place and not harmful at all.

So, let’s imagine this scenario:

  • VMWare Server 1.0.2 (other versions might apply as well, not tested thought)
  • Debian Linux 4.0 Etch guest, running 2.6.18-6-686 kernel (other versions might apply as well, not tested thought)
  • VMWare Tools 1.0.2-39867 (other versions might apply as well, not tested thought)

Then, after the VMWare Tools get installed, the screen shows something like this:

The configuration of VMware Tools 1.0.2 build-39867 for Linux for this running
kernel completed successfully.

You must restart your X session before any mouse or graphics changes take
effect.

You can now run VMware Tools by invoking the following command:
"/usr/bin/vmware-toolbox" during an X session.

To use the vmxnet driver, restart networking using the following commands:
/etc/init.d/networking stop
rmmod pcnet32
rmmod vmxnet
depmod -a
modprobe vmxnet
/etc/init.d/networking start

Enjoy,

--the VMware team

Right now the networking does not work. If you try to see what is going on, you should see something like this:

ifconfig

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:15 errors:0 dropped:0 overruns:0 frame:0
          TX packets:15 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1556 (1.5 KiB)  TX bytes:1556 (1.5 KiB)

That’s it. No network interfaces. If you go for VMWare Tools’ installer suggested steps, the networking should work again:

/etc/init.d/networking stop
rmmod pcnet32
rmmod vmxnet
depmod -a
modprobe vmxnet
/etc/init.d/networking start

E.g.:

ifconfig

eth0      Link encap:Ethernet  HWaddr 00:0C:29:23:95:ED
          inet addr:10.123.16.83  Bcast:10.123.16.255  Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fe23:95ed/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:4425 errors:0 dropped:0 overruns:0 frame:0
          TX packets:7426 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:316655 (309.2 KiB)  TX bytes:494628 (483.0 KiB)
          Interrupt:169 Base address:0x1424

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:15 errors:0 dropped:0 overruns:0 frame:0
          TX packets:15 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1556 (1.5 KiB)  TX bytes:1556 (1.5 KiB)

The issue here is that this settings will be lost upon restart. I guess it is a matter of having the proper modules loaded properly but I have not been able to find the proper configuration files combination to get this reliably enough.

Proposed solution/workaround

Basically, create a simple script that does what VMWare Tools’ intaller suggests and have it invoked upon system restart.

The script should contain the following:

#! /bin/bash
#
# vmxnet driver loader - loads the vmware network driver.
#
#

PATH=/sbin:/bin:/usr/sbin:/usr/bin

/etc/init.d/networking stop
rmmod pcnet32
rmmod vmxnet
depmod -a
modprobe vmxnet
/etc/init.d/networking start

This file should be created under /etc/init.d folder, with 755 permissions (i.e. chmod 755 filename). The, to have it invoken upon restart you could do this:

update-rc.d vmxnet-loader defaults 10
 Adding system startup for /etc/init.d/vmxnet-loader ...
   /etc/rc0.d/K10vmxnet-loader -> ../init.d/vmxnet-loader
   /etc/rc1.d/K10vmxnet-loader -> ../init.d/vmxnet-loader
   /etc/rc6.d/K10vmxnet-loader -> ../init.d/vmxnet-loader
   /etc/rc2.d/S10vmxnet-loader -> ../init.d/vmxnet-loader
   /etc/rc3.d/S10vmxnet-loader -> ../init.d/vmxnet-loader
   /etc/rc4.d/S10vmxnet-loader -> ../init.d/vmxnet-loader
   /etc/rc5.d/S10vmxnet-loader -> ../init.d/vmxnet-loader

I suggest having the initscript invoked with a lower sequence code (i.e. 10) so the networking gets activated before other services which may use and/or need it.

That’s it. Now your virtual machine’s networking should be fine upon restarts.

See Also

HAProxy 1.3.15.2 installation under Debian Etch (compiling from sources)

HAProxy is an excellent load balancer which performs extremely well. This page explains how to install HAProxy 1.3.15.2 since this is one of the recommended versions on the ”HAProxy Mailing List”:

Server response time discrepancy

Also, it has been recommended on that thread to use one of the following kernels:

  • 2.6.22
  • 2.6.25
  • 2.6.18

Installation Steps

First, install some required tools/packages:

apt-get update
apt-get install build-essential make libpcre3 libpcre3-dev

If you want to stick to one of the recommended kernels, at the time this how-to was written, Debian Etch standard apt-get repositories include the kernel 2.6.18, which could be installed (optional):

apt-get install linux-kernel-headers

Then you should reboot after, to start using this new kernel.

If you want to find out which kernel you are using, you may want to run this:

uname -rs

The output should be something like this:

Linux 2.6.18-6-686

Now, you should configure syslog daemon to listen following this document:

Configuring syslog to receive messages from the network (aka listen)

Check the HAProxy’s README file, and make sure:

To build haproxy, you will need :

  • GNU make. Neither Solaris nor OpenBSD’s make work with this makefile. However, specific Makefiles for BSD and OSX are provided.
  • GCC between 2.91 and 4.3. Others may work, but not tested.
  • GNU ld

Proceed with the compilation as follows (note that I have used TARGET, CPU and USE_PCRE. These options need to be double checked on the readme file, it is very clear):

cd /opt/
wget http://haproxy.1wt.eu/download/1.3/src/haproxy-1.3.15.2.tar.gz
tar zxvf haproxy-1.3.15.2.tar.gz

#
# Double check your options on the readme file first!!!!
# http://sysbible.org/att/HAProxy-1.3.15_README.txt
#
cd /opt/haproxy-1.3.15.2
make TARGET=linux26 CPU=i686 USE_PCRE=1
make install

ln -s /usr/local/sbin/haproxy /usr/sbin/haproxy

Now you should be ready to go:

haproxy

HA-Proxy version 1.3.15.2 2008/06/21
Copyright 2000-2008 Willy Tarreau

Usage : haproxy -f  [ -vdVD ] [ -n  ] [ -N  ]
        [ -p
 ] [ -m  ]
        -v displays version ; -vv shows known build options.
        -d enters debug mode ; -db only disables background mode.
        -V enters verbose mode (disables quiet mode)
        -D goes daemon ; implies -q
        -q quiet mode : don't display messages
        -c check mode : only check config file and exit
        -n sets the maximum total # of connections (2000)
        -m limits the usable amount of memory (in MB)
        -N sets the default, per-proxy maximum # of connections (2000)
        -p writes pids of all children to this file
        -de disables epoll() usage even when available
        -ds disables speculative epoll() usage even when available
        -dp disables poll() usage even when available
        -sf/-st [pid ]* finishes/terminates old pids. Must be last arguments.
haproxy -vv

HA-Proxy version 1.3.15.2 2008/06/21
Copyright 2000-2008 Willy Tarreau

Build options :
  TARGET  = linux26
  CPU     = i686
  CC      = gcc
  CFLAGS  = -O2 -march=i686 -g
  OPTIONS = USE_PCRE=1

Forcing Perl to install CPAN packages via HTTP (i.e. avoiding FTP)

If you are behind a firewall and your FTP connectivity with the external world is just restricted you might get frustrated with Perl’s automatic way of installing packages (via CPAN) because it uses FTP protocol by default.

Solution

Edit your CPAN settings file (probably /etc/perl/CPAN/Config.pm) and change the line:

'urllist' => [],

it should look like this:

'urllist' => [q[http://www.perl.com/CPAN]],

After that you should be able to install automatically CPAN modules using http protocol instead of ftp.

See Also

Installing unrar package under Debian Linux

What we need to do is install this package (at least for Debian 4.0 Etch. You may find for your appropriate version here). Since it belongs to Debian’s non-free section you need to make sure you have non-free enabled on your apt sources.

You may test that everything will be smooth by invoking the install command with the “simulate” switch (-s):

apt-get update
apt-get -s install unrar

Building Dependency Tree... Done
The following NEW packages will be installed:
  unrar
0 upgraded, 1 newly installed, 0 to remove and 82 not upgraded.
Inst unrar (1:3.5.2-0.1 Debian:3.1r7/oldstable)
Conf unrar (1:3.5.2-0.1 Debian:3.1r7/oldstable)

It actually looks OK; there are no dependency problems and the upgrade is minimal (this package does not require to install many others). I then proceed with the “real” thing:

apt-get install unrar

Reading Package Lists... Done
Building Dependency Tree... Done
The following NEW packages will be installed:
  unrar
0 upgraded, 1 newly installed, 0 to remove and 82 not upgraded.
Need to get 87.9kB of archives.
After unpacking 221kB of additional disk space will be used.
Get:1 http://mirror.aarnet.edu.au oldstable/non-free unrar 1:3.5.2-0.1 [87.9kB]
Fetched 87.9kB in 1s (53.2kB/s)
Selecting previously deselected package unrar.
(Reading database ... 47406 files and directories currently installed.)
Unpacking unrar (from .../unrar_1%3a3.5.2-0.1_i386.deb) ...
Setting up unrar (3.5.2-0.1) ...

Unrar command line usage under Debian Linux

The command usage is:

Usage:     unrar  - -  
                


  e             Extract files to current directory
  l[t,b]        List archive [technical, bare]
  p             Print file to stdout
  t             Test archive files
  v[t,b]        Verbosely list archive [technical,bare]
  x             Extract files with full path


  -             Stop switches scanning
  ad            Append archive name to destination path
  ap      Set path inside archive
  av-           Disable authenticity verification check
  c-            Disable comments show
  cfg-          Disable read configuration
  cl            Convert names to lower case
  cu            Convert names to upper case
  dh            Open shared files
  ep            Exclude paths from names
  ep3           Expand paths to full including the drive letter
  f             Freshen files
  id1   Disable messages
  ierr          Send all messages to stderr
  inul          Disable all messages
  kb            Keep broken extracted files
  n       Include only specified file
  n@            Read file names to include from stdin
  n@      Include files in specified list file
  o+            Overwrite existing files
  o-            Do not overwrite existing files
  ow            Save or restore file owner and group
  p[password]   Set password
  p-            Do not query password
  r             Recurse subdirectories
  ta      Process files modified after  in YYYYMMDDHHMMSS format
  tb      Process files modified before  in YYYYMMDDHHMMSS format
  tn      Process files newer than 
  to      Process files older than 
  ts[N]  Save or restore file time (modification, creation, access)
  u             Update files
  v             List all volumes
  ver[n]        File version control
  vp            Pause before each volume
  x       Exclude specified file
  x@            Read file names to exclude from stdin
  x@      Exclude files in specified list file
  y             Assume Yes on all queries

See Also