Posts Tagged ‘mysql servers’

Create SSH Tunnel to MySQL server to access remote filtered MySQL port 3306 host through localhost port 3308

Friday, February 27th, 2015

create_ssh_tunnel_to-mysql_server-to-access-remote-filtered-mysql-on-port-3306-secure_ssh_traffic
On our Debian / CentOS / Ubuntu Linux and Windows servers we're running multiple MySQL servers and our customers sometimes need to access this servers.
This is usually problem because MySQL Db  servers are running in a DMZ Zone with a strong firewall and besides that for security reasons SQLs are configured to only listen for connections coming from localhost, I mean in config files across our Debian Linux servers and CentOS / RHEL Linux machines the /etc/mysql/my.cnf and /etc/my.cnf the setting for bind-address is 127.0.0.1:
 

[root@centos ~]# grep -i bind-address /etc/my.cnf 
bind-address            = 127.0.0.1
##bind-address  = 0.0.0.0


For source code developers which are accessing development SQL servers only through a VPN secured DMZ Network there are few MySQL servers witha allowed access remotely from all hosts, e.g. on those I have configured:
 

[root@ubuntu-dev ~]# grep -i bind-address /etc/my.cnf 

bind-address  = 0.0.0.0


However though clients insisted to have remote access to their MySQL Databases but since this is pretty unsecure, we decided not to configure MySQLs to listen to all available IP addresses / network interfaces. 
MySQl acess is allowed only through PhpMyAdmin accessible via Cleint's Web interface which on some servers is CPanel  and on other Kloxo (This is open source CPanel like very nice webhosting platform).

For some stubborn clients which wanted to have a mysql CLI and MySQL Desktop clients access to be able to easily analyze their databases with Desktop clients such as MySQL WorkBench there is a "hackers" like work around to create and use a MySQL Tunnel to SQL server from their local Windows PCs using standard OpenSSH Linux Client from Cygwin,  MobaXterm which already comes with the SSH client pre-installed and has easy GUI interface to create SSH tunnels or eventually use Putty's Plink (Command Line Interface) to create the tunnel

Anyways the preferred and recommended (easiest) way to achieve a tunnel between MySQL and local PC (nomatter whether Windows or Linux client system) is to use standard ssh client and below command:
 

ssh -o ServerAliveInterval=10 -M -T -M -N -L 3308:localhost:3306 your-server.your-domain.com


By default SSH tunnel will keep opened for 3 minutes and if not used it will automatically close to get around this issue, you might want to raise it to (lets say 15 minutes). To do so in home directory user has to add in:
 

~/.ssh/config

ServerAliveInterval 15
ServerAliveCountMax 4


Note that sometimes it is possible ven though ssh tunnel timeout value is raised to not take affect if there is some NAT (Network Adress Translation) with low timeout setting on a firewall level. If you face constant SSH Tunnel timeouts you can use below bash few lines code to auto-respawn SSH tunnel connection (for Windows users use MobaXterm or install in advance bash shell cygwin package):
 

while true
do
 
ssh -o ServerAliveInterval=10 -M -T -M -N -L 3308:localhost:3306 your-server.your-domain.com
  sleep 15
done


Below is MySQLBench screenshot connected through server where this blog is located after establishing ssh tunnel to remote mysql server on port 3308 on localhost

mysql-workbench-database-analysis-and-management-gui-tool-convenient-for-data-migratin-and-queries-screenshot-

There is also another alternative way to access remote firewall filtered mysql servers without running complex commands to Run a tunnel which we recommend for clients (sql developers / sql designers) by using HeidiSQL (which is a useful tool for webdevelopers who has to deal with MySQL and MSSQL hosted Dbs).

heidisql-show-host_processlist-screenshot

To connect to remote MySQL server through a Tunnel using Heidi:

mysql_connection_configuration-heidi-mysql-gui-connect-tool

 

In the ‘Settings’ tab

1. In the dropdown list of ‘Network type’, please select SSH tunnel

2. Hostname/IP: localhost (even you are connecting remotely)

3. Username & Password: your mysql user and password

Next, in the tab SSH Tunnel:

1. specify plink.exe or you need to download it and specify where it’s located

2. Host + port: the remote IP of your SSH server(should be MySQL server as well), port 22 if you don’t change anything

3. Username & password: SSH username (not MySQL user)

 

heidi-connection_ssh_tunnel_configuration-heidi-sql-tool-screenshot
 

Alternative way to enter as administrator in MySQL if you forgot MySQL root password on Debian Linux

Wednesday, July 10th, 2013

Forgot MySQL password root alternative way to enter as administrator in MyQL MySQL logo with 2 dolphins

Whether you have to administrate a bunch of chaotic organized MySQL servers and amount of work is more than you can bear it is very common you make stupid mistakes, like loosing MySQL root adminsitrator password. There is way to recover password by stopping SQL server and starting it with –skip-grant-tables options via SSH , however if you do it that way there is at least few seconds of down time and as its not a good idea on productive servers Debian and Ubuntu Linux admins have better way to do it by using MySQL default user used to check whether all is fine with database on MySQL server initialization via /etc/init.d/mysql. User with GRANT PRIVILEGES, (all MySQL administrator users have grant privileges) on Debian based distributions is debian-sys-maint and whether you have root access to server you can easily obtain password with:

# grep -i -E 'user|pass' /etc/mysql/debian.cnf |uniq

user = debian-sys-maint

password = k6x6tBUBfHN3ZxHv

Using this password then you can login via mysql cli or via PhpMyAdmin, whether installed and do any normal SQL operation you do as root. Of course having this password in plain text file can be very dangerous, by default it is configured to be only red by root be careful not to change this permissions by default as anyone who has access to system can then access your SQL as administrator.
To reset MySQL root password once logged in run:

UPDATE USER set password=PASSWORD('NEW_PASS_WORD') where USER='root';
FLUSH PRIVILEGES;

Enjoy 😉
 

Script to Automatically change current MySQL server in wp-config.php to another MySQL host to minimize WordPress and Joomla downtimes

Friday, July 20th, 2012

I'm running a two servers for a couple of home hosted websites. One of the servers is serving as Apache host1 and has configured MySQL running on it and the second is used just for database host2 – (has another MySQL configured on it).
The MySQL servers are not configured to run as a MySQL MASTER and MySQL SLAVE (no mysql replication), however periodically (daily), I have a tiny shell script that is actualizing the data from the active SQL host2 server to host1.

Sometimes due to electricity problems or CPU overheats the active MySQL host at host2 gets stoned and stops working causing the 2 WordPress based websites and One joomla site inaccessible.
Until I manually get to the machine and restart host2 the 3 sites are down from the net and as you can imagine this has a very negative impact on the existing website indexing (PageRank) in Google.

When I'm at home, this is not a problem as I have physical access to the servers and if somethings gets messy I fix it quickly. The problem comes, whether I'm travelling or in another city far from home and there is no-one at home to give the hanged host hard reboot ….

Lately the problems with hang-ups of host2 happaned 3 times or so for 2 weeks, as a result the websites were inaccessible for hours and since there is nobody to reboot the server for hours; the websites keep hanging until the DB host is restarted ;;;;

To work-around this I came with the idea to write a tiny shell script to check if host2 is ping-able in order to assure the Database host is not down and then if script determines host2 (mysql) host is down it changes wp-config.php (set to use host2) to a wp-config.php (which I have beforehand configured to use) host1.

Using the script is a temporary solution, since I have to actually find the real hang-up causing troubles, but at least it saves me long downtimes. Here is a download link to the script I called change_blog_db.sh .
I've configured the script to be run on the Apache node (host1) via a crontab calling the script every 10 minutes, here is the crontab:
 

*/10 * * * * /usr/sbin/change_blog_db.sh > /dev/null 2>&1

The script is written in a way so if it determins host2 is reachable a copy of wp-config.php and Joomla's configuration.php tuned to use host2 is copied over the file config originals. In order to use the script one has to configured the head variables script section, e.g.:

host_to_ping='192.168.0.2';
blog_dir='/var/www/blog';
blog_dir2='/var/www/blog1';blog_dir3='/var/www/joomla';
notify_mail='hipo@pc-freak.net';
wp_config_orig='wp-config.php';
wp_config_localhost='wp-config-localhost.php';
wp_config_other_host='wp-config-192.168.0.2.php';
joomla_config_orig='configuration.php';
joomla_config_other_host='configuration-192.168.0.2.php';

You will have to manually prepare;;;

wp-config-localhost.php, wp-config-192.168.0.2.php ,configuration-192.168.0.2.php, wp-config-localhost.php to be existing files configured to with proper host1 and host2 IP addresses.
Hope the script will be useful to others, experiencing database downtimes with WordPress or Joomla installs.
 

How to tune MySQL Server to increase MySQL performance using mysqltuner.pl and Tuning-primer.sh

Tuesday, August 9th, 2011

MySQL Easy performance tuning with mysqltuner.pl and Tuning-primer.sh scripts

Improving MySQL performance is crucial for improving a website responce times, reduce server load and improve overall work efficiency of a mysql database server.

I’ve seen however many Linux System administrators who does belittle or completely miss the significance of tuning a newly installed MySQL server installation.
The reason behind that is probably caused by fact that many people think MySQL config variables, would not significantly improve performance and does not pay back for optimization efforts. Moreover there are a bunch of system admins who has to take care for numerous services so they don’t have time to get good knowledge to optimize MySQL servers.
Thus many admins and webmasters nowdays, think optimizations depend mostly on the side of the website programmers.
It’s also sometimes falsely believed that optimizing a MySQL server could reduce the overall server stability.

With the boom of Internet website building and internet marketing, many webmasters emerged and almost anybody with almost no knowledge on GNU/Linux or minimal or no knowledge on PHP can start his Online store, open a blog or create a website powered by some CMS like joomla.
Thus nowdays many servers even doesn’t have a hired system administrators but are managed by people whose knowledge on *Nix is almost next to zero, this is another reason why dozens of MySQL installations online are a default ones and are not taking a good advantage of the server hardware.

The incrase of website visitors leads people servers expectations for hardware also to grow, thus many companies simply buy a new hardware instead of taking the few time to investigate on how current server hardware can be utilized better.
In that manner of thought I though it will be a good idea to write this small article on Tuning mysql servers with two scripts Tuning-primer.sh and mysqltuner.pl.
The scripts are ultra easy to use and does not require only a minimal knowledge on MySQL, Linux or (*BSD *nix if sql is running on BSD).
Tuning-primer.sh and mysqltuner.pl are therefore suitable for a quick MySQL server optimizations to even people who are no computer experts.

I use this two scripts for MySQL server optimizations on almost every new configured GNU/Linux with a MySQL backend.
Use of the script comes to simply download with wget, lynx, curl or some other web client and execute it on the server host which is already running the MySQL server.

Here is an example of how simple it is to run the scripts to Optimize MySQL:

debian:~# perl mysqltuner.pl
>> MySQLTuner 1.2.0 - Major Hayden >major@mhtx.net<
>> Bug reports, feature requests, and downloads at http://mysqltuner.com/
>> Run with '--help' for additional options and output filtering

——– General Statistics ————————————————–
[–] Skipped version check for MySQLTuner script
[OK] Currently running supported MySQL version 5.1.49-3
[OK] Operating on 64-bit architecture

——– Storage Engine Statistics ——————————————-
[–] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster
[–] Data in MyISAM tables: 6G (Tables: 952)
[!!] InnoDB is enabled but isn’t being used
[!!] Total fragmented tables: 12

——– Security Recommendations ——————————————-
[OK] All database users have passwords assigned

——– Performance Metrics ————————————————-
[–] Up for: 1d 2h 3m 35s (68M q [732.193 qps], 610K conn, TX: 49B, RX: 11B)
[–] Reads / Writes: 76% / 24%
[–] Total buffers: 512.0M global + 2.8M per thread (2000 max threads)
[OK] Maximum possible memory usage: 6.0G (25% of installed RAM)
[OK] Slow queries: 0% (3K/68M)
[OK] Highest usage of available connections: 7% (159/2000)
[OK] Key buffer size / total MyISAM indexes: 230.0M/1.7G
[OK] Key buffer hit rate: 97.8% (11B cached / 257M reads)
[OK] Query cache efficiency: 76.6% (46M cached / 61M selects)
[!!] Query cache prunes per day: 1822075
[OK] Sorts requiring temporary tables: 0% (1K temp sorts / 2M sorts)
[!!] Joins performed without indexes: 63635
[OK] Temporary tables created on disk: 1% (26K on disk / 2M total)
[OK] Thread cache hit rate: 99% (159 created / 610K connections)
[!!] Table cache hit rate: 4% (1K open / 43K opened)
[OK] Open file limit used: 17% (2K/16K)
[OK] Table locks acquired immediately: 99% (36M immediate / 36M locks)

——– Recommendations —————————————————–
General recommendations:
Add skip-innodb to MySQL configuration to disable InnoDB
Run OPTIMIZE TABLE to defragment tables for better performance
Enable the slow query log to troubleshoot bad queries
Increasing the query_cache size over 128M may reduce performance
Adjust your join queries to always utilize indexes
Increase table_cache gradually to avoid file descriptor limits
Variables to adjust:
query_cache_size (> 256M) [see warning above] join_buffer_size (> 256.0K, or always use indexes with joins) table_cache (> 7200)

You see there are plenty of things, the script reports, for the unexperienced most of the information can be happily skipped without need to know the cryptic output, the section of importance here is Recommendations for some clarity, I’ve made this section to show up bold.

The most imporant things from the Recommendations script output is actually the lines who give suggestions for incrase of certain variables for MySQL.In this example case this are the last three variables:
query_cache_size,
join_buffer_size and
table_cache

All of these variables are tuned from /etc/mysql/my.cnf (on Debian) and derivatives distros and from /etc/my.cnf on RHEL, CentOS, Fedora and the other RPM based Linux distributions.

On some custom server installs my.cnf is also located in /usr/local/mysql/etc/ or some other a bit more unstandard location 😉

Anyways now having the Recommendation from the script, it’s necessery to edit my.cnf and try to double the values for the suggested variables.

First, I check if all the suggested variables are existent in my config with grep , if they’re not then I’ll simply add the variable with doubled size of the suggested values.
P.S: One note here is sometimes some values which are configured, are the default value for the MySQL server and does not have a record in my.cnf

debian:~# grep -E 'query_cache_size|join_buffer_size|table_cache' /etc/mysql/my.cnf table_cache = 7200
query_cache_size = 256M
join_buffer_size = 262144

All of my variables are in the config so, now edit my.cnf and set values to:
table_cache = 14400
query_cache_size = 512M
join_buffer_size = 524288

I always, however preserve the old variable’s value, because sometimes raising the value might create problem and the MySql server might be unable to restart properly.
Thus before going with adding the new values make sure the old ones are commented with # , e.g.:
#table_cache = 7200
#query_cache_size = 256M
#join_buffer_size = 262144

I would recommend vim as editor of choice while editing my.cnf as vim completely rox 😉 If you’re not acquainted to vim use nano or mcedit or your editor of choice 😉 :

debian:~# vim /etc/mysql/my.cnf
...

Assuming that the changes are made, it’s time to restart MySQL to make sure the new values are read by the SQL server.

debian:~# /etc/init.d/mysql restart
* Stopping MySQL database server mysqld [ OK ]
* Starting MySQL database server mysqld [ OK ]
Checking for tables which need an upgrade, are corrupt or were not closed cleanly.

If mysql server fails, however to restart, make sure immediately you reverse back the changed variables to the commented values and restart once again via mysql init script to make server load.

Afterwards start adding the values one by one until find out which one is causing the mysqld to fail.

Now the second script (Tuning-primer.sh) is also really nice for MySQL performance optimizations are necessery. However it’s less portable (as it’s written in bash scripting language).
Consider running this script among different GNU/Linux distributious (especially the newer ones) might produce errors.
Tuning-primer.sh requires some minor code changes to be able to run on FreeBSD, NetBSD and OpenBSD *nices.

The way Tuning-primer.sh works is precisely like mysqltuner.pl , one runs it it gives some info about current running MySQL server and based on certain factors gives suggestions on how increasing or decresing certain my.cnf variables could reduce sql query bottlenecks, solve table locking issues as well as generally improve INSERT, UPDATE query times.

Here is an example output from tuning-primer.sh run on another server:

server:~# wget http://www.pc-freak.net/files/Tuning-primer.sh
...
server:~# sh Tuning-primer.sh
-- MYSQL PERFORMANCE TUNING PRIMER --
- By: Matthew Montgomery -

MySQL Version 5.0.51a-24+lenny5 x86_64

Uptime = 8 days 10 hrs 19 min 8 sec
Avg. qps = 179
Total Questions = 130851322
Threads Connected = 1

Server has been running for over 48hrs.
It should be safe to follow these recommendations

To find out more information on how each of these
runtime variables effects performance visit:
http://dev.mysql.com/doc/refman/5.0/en/server-system-variables.html

SLOW QUERIES
Current long_query_time = 1 sec.
You have 16498 out of 130851322 that take longer than 1 sec. to complete
The slow query log is NOT enabled.
Your long_query_time seems to be fine

MAX CONNECTIONS
Current max_connections = 2000
Current threads_connected = 1
Historic max_used_connections = 85
The number of used connections is 4% of the configured maximum.
Your max_connections variable seems to be fine.

WORKER THREADS
Current thread_cache_size = 128
Current threads_cached = 84
Current threads_per_sec = 0
Historic threads_per_sec = 0
Your thread_cache_size is fine

MEMORY USAGE
Tuning-primer.sh: line 994: let: expression expected
Max Memory Ever Allocated : 741 M
Configured Max Memory Limit : 5049 M
Total System Memory : 23640 M

KEY BUFFER
Current MyISAM index space = 1646 M
Current key_buffer_size = 476 M
Key cache miss rate is 1 / 56
Key buffer fill ratio = 90.00 %
You could increase key_buffer_size
It is safe to raise this up to 1/4 of total system memory;
assuming this is a dedicated database server.

QUERY CACHE
Query cache is enabled
Current query_cache_size = 64 M
Current query_cache_used = 38 M
Current Query cache fill ratio = 59.90 %

SORT OPERATIONS
Current sort_buffer_size = 2 M
Current record/read_rnd_buffer_size = 256.00 K
Sort buffer seems to be fine

JOINS
Current join_buffer_size = 128.00 K
You have had 111560 queries where a join could not use an index properly
You have had 91 joins without keys that check for key usage after each row
You should enable “log-queries-not-using-indexes”
Then look for non indexed joins in the slow query log.
If you are unable to optimize your queries you may want to increase your
join_buffer_size to accommodate larger joins in one pass.

TABLE CACHE
Current table_cache value = 3600 tables
You have a total of 798 tables
You have 1904 open tables.
The table_cache value seems to be fine

TEMP TABLES
Current tmp_table_size = 128 M
1% of tmp tables created were disk based
Created disk tmp tables ratio seems fine

TABLE SCANS
Current read_buffer_size = 128.00 K
Current table scan ratio = 797 : 1
read_buffer_size seems to be fine

TABLE LOCKING
Current Lock Wait ratio = 1 : 1782
You may benefit from selective use of InnoDB.

As seen from script output, there are certain variables which might be increased a bit for better SQL performance, one such variable as suggested is key_buffer_size(You could increase key_buffer_size)

Now the steps to make the tunings to my.cnf are precisely the same as with mysqltuner.pl, e.g.:
1. Preserve old config variables which will be changed by commenting them
2. Double value of current variables in my.cnf suggested by script
3. Restart Mysql server via /etc/init.d/mysql restart cmd.
4. If mysql runs fine monitor mysql performance with mtop or mytop for at least 15 mins / half an hour.

if all is fine run once again the tuning scripts to see if there are no further improvement suggestions, if there are more follow the 4 steps described procedure once again.

It’s also a good idea that these scripts are periodically re-run on the server like once per few months as changes in SQL queries amounts and types will require changes in MySQL operational variables.
The authors of these nice scripts has done great job and have saved us a tons of nerves time, downtimes and money spend on meaningless hardware. So big thanks for the awesome scripts guys 😉
Finally after hopefully succesful deployment of changes, enjoy the incresed SQL server performance 😉

How to make a mysql root user to login interactive with mysql cli passwordless

Wednesday, June 29th, 2011

MySQL Logo Passwordless root login .my.cnf

I’m using access to the mysql servers via localhost with mysql cli on daily basis.
With time I’ve figured out that it’s pretty unahandy to always login with my root mysql password, I mean each time to enter it, e.g.:

root@mysql-server:~# mysql -u root
Enter password:
...

Thus to make my life a way easier I decided to store my mysql root password in order to allow my root admin user to be able to login to my mysql server without asking for password. This saves time and nerves, as I’m not supposed to look up for the password file I store my server mysql root pass.

To allow my mysql cli interface, to login passwordless to the SQL server I had to create the file /root/.my.cnf readable only for my root user and store my MySQL username and password there.

Here is a sample /root/.my.cnf file:

root@mysql-server:~# cat /root/.my.cnf
[client]
user="root"
pass="mysecretMySQLPasswordgoeshere"

Now next time I use the mysql console interface to access my mysql server I don’t have to supply the password, here is how easier is the mysql login afterwards:

root@mysql-server:~# mysql -u root
Welcome to the MySQL monitor. Commands end with ; or g.
Your MySQL connection id is 3520
Server version: 5.0.77 Source distribution

Type ‘help;’ or ‘h’ for help. Type ‘c’ to clear the buffer.

mysql>

The only downside of using .my.cnf to store permanently the mysql server root and password is from security standpoint.
If for instance somebody roots my servers, where I have stored my root user/pwds in .my.cnf , he will be able immediately to get access to the MySQL server.

Another possible security flaw with using the mysql passwordless login “trick” is if somebody forgets to set proper file permissions to, .my.cnf

Once again the file should possess the permissons of:

root@mysql-server:~# ls -al /root/.my.cnf
-rw------- 1 root root 90 Apr 2 00:05 /root/.my.cnf

Any other permissons might allow non-privileged users to read the file and gain unathorized admin access to the SQL server.
 

How to set password on a mysql server with no password via mysql command line interface

Monday, March 28th, 2011

Many Linux distributions’s offered MySQL server comes without a set default password, in practice you can freely login to the mysql server on a plain mysql server installation on Debian, Ubuntu or Fedora by simply issuing:

linux:~# mysql -u root
Enter password:

Pressing enter will straight let you in the mysql server. The same kind of behaviour is also probably true on BSD based and many other Unixes which have pre-installed or the option to install a new mysql server.

I remember in my past that I’ve even seen a productive mysql servers on a servers running CMS based websites which doesn’t have a root password set.

Some administrators doesn’t take the time to think about the implications of the no password mysql installation and therefore being in a hurry simply let the server without an administrator password.
This is very common for the most lame and uneducated ones. Many novice system administrators think that by installing a phpmyadmin and configuring a password on it’s web interface is equal to setting up the mysql server (daemon) a password.

Thus for all this the uneducated ones and for all those who already have noticed that their newly installed mysql server doesn’t have a password set I’ve decided to give an example how a new mysql server password can be set or how an existing mysql server pass can be changed to a new one

To make any password manipulations usually the mysql-client package does provide a very handy instrument called mysqladmin , mysqladmin has many possibilities among which is creating a new mysql server admin (root) password or changing a previously set mysql server password to a new one

1. Here is how you can set a new MySQL server password:

mysqladmin -u root 'password' YOURasddsaPASSWORDjqweHERE

2. If you need to change an already existing mysql password you need to provide just one more argument to mysqladmin:

mysqladmin -u root 'password' YOURasdfdsaNEWasddsaPASSWORD_HERE -pEnter password:

Whether the Enter password: field appears you will be required to fill in the original mysql server root password after which the password will be changed to the above string passed in to the mysqladmin command line ‘YOURasdfdsaNEWasddsaPASSWORD_HERE’

That’s all now you have either set a new password for the mysql server or have already changed your previous one.

How to revoke user global privileges in MySQL

Saturday, August 14th, 2010

I’ve recently realized one of the users I have added to one of the MySQL servers I do managehas actually some included a list of some of the global privileges.
This extra privileges the user had was actually something that was to be removed since theuser is not supposed to be able to list all existent databases on the MySQL server and things alike:

You can see below the excact SQL queries I had to issue to revoke the granted global privileges for the username.
Note to change the username before you execute the below queries:

REVOKE ALL PRIVILEGES ON * . * FROM 'username'@'localhost';
REVOKE GRANT OPTION ON * . * FROM 'username'@'localhost';
GRANT USAGE ON * . * TO 'username'@'localhost' WITH MAX_QUERIES_PER_HOUR 0 MAX_CONNECTIONS_PER_HOUR 0 MAX_UPDATES_PER_HOUR 0 MAX_USER_CONNECTIO