Limiting a User to Read few columns on a table in MySQL Database

I wanted to limit a mysql user to read only few fields of a table in a MySQL database. I used select grant privileges command to get the desired output.

For example if a user 'test_user' is requested to access field1, field3 and field6 on the test_table in test_db at 192.168.1.1 server following user creation will work.

The user has to be added at the mysql server running on 192.168.1.1. I have assumed the user test_user is connecting from 192.168.1.2

mysql> GRANT SELECT (`field1` ,`field3`, `field6`)  ON `test_db`.`test_table` TO 'test_user'@'192.168.1.2' identified by 'test_pw';


If you want to allow the user to modify the data in the table you may use 'UPDATE' privilege instead of 'SELECT' privilege.

References

• http://dba.stackexchange.com/questions/45708/allow-select-on-specific-column-only
• http://dev.mysql.com/doc/refman/5.1/en/grant.html#grant-column-privileges

How to monitor user login history on CentOS with utmpdump

A very useful reading for CentOS admins http://xmodulo.com/2014/09/monitor-user-login-history-centos-utmpdump.html.

I was using `last` and `lastb` earlier but feels we can get more information with `utmpdump`. Thanks for Gabriel Cánepa for his article.

Some short notes from his article

utmpdump /var/run/utmp  - show who is currently logged on and what they are doing, and also by uptime to display system up time

utmpdump /var/log/wtmp -  show the listing of last logged-in users

utmpdump /var/log/btmp  - show the listing of last failed login attempts

These files are used in last and `lastb` commands to show details of login but by using utmpdump we get more flexibility for filtering

Upgrade PHP 5.3.3 to 5.4 in CentOS

Sometimes we need to upgrade PHP version inbuilt with the OS to newer version. We have been using CentOS for sometimes. It was requested to upgrade PHP to php5.4 in CentOS 6.5 and I have followed the below given link. We were able to upgrade PHP 5.3.3 to  PHP 5.4.32 (cli) (built: Aug 22 2014 07:07:38) smoothly.

If you have such requirement it is safe to follow the link http://www.shayanderson.com/linux/centos-5-or-centos-6-upgrade-php-to-php-54-or-php-55.htm

Even though it is bit old still works fine :-)

Issue with Roundcube when sending Mails

Today we encountered a strange issue after reboot the server running roundcube webmail application. I was able to login to the webmail application over the network, read mails (I received mails) BUT was not able to send mails. The message says nothing but

'could not send mail. Please wait 76531921 seconds'.

I was clueless as the server had no issue with connecting to sendmail server, web server. No issues were detected in SELinux/iptables/network etc.All the services were OK.

Finally we checked the date and time of the server and found the date had reset to past data in 2012... This had confused the webmail service when the users try to send mails.

After reset the data to current settings, all went OK.

ntpdate -u <ntpserverip>

Moral:
There could be a totally strange reason for an issue. You need to check all possibilities without get panic.

Display Time in Horde IMP

I have faced the issue of displaying date/time in Horde IMP mail client in several occasions. I have rectified those issues but failed to post it in my blog.

OK, today I had the same issue with Horde Groupware 5.1.4 IMP mail client. It displayed a wrong time for the mail arrival time.

As Horde uses PHP functions for time variable settings, the time zone setting in php.ini should be corrected according to your standard time zone.

[Date]
; Defines the default timezone used by the date functions
; http://www.php.net/manual/en/datetime.configuration.php#ini.date.timezone
date.timezone ="Asia/Colombo"

Replace "Asia/Colombo" with your preferred time zone, and horde will display the correct mail arrival times accordingly.