LinuxHostingSupport

The ‘mock’ module is responsible to build the source RPMs (SRPMs) under a chroot environment and uses the ‘mockbuild’ user.

If the mockbuild user does not exist while installing the source RPM, you will receive the ‘Warning: user mockbuild does not exist. using root‘ error message.

In order to fix the warning message, install the ‘mock’ module:

# yum install mock

and create the ‘mockbuild’ user

# useradd -s /sbin/nologin mockbuild

Once done, you should be able to install the required tool under the mockbuild user.

When Apache is compiled as CGI/SuPHP, it allows users to create their own php.ini file under their home directory and modify the php values as per their wish.

This may increase security concerns on the server and hence to protect/secure php.ini in SuPHP enabled servers, force every user to use a common php.ini file.

This can be achieved by defining the path of server side php.ini file using suPHP_ConfigPath directive. To force users to use server side php.ini file, create suphp_configpath.conf

# pico /usr/local/apache/conf/userdata/suphp_configpath.conf

and add the following lines

<IfModule mod_suphp.c>
<Location />
suPHP_ConfigPath /usr/local/lib/
</Location>
</IfModule>

Once done, save the file and rebuild the Apache configuration so it picks up the changes.

# /usr/local/cpanel/bin/apache_conf_distiller --update --main
# /usr/local/cpanel/bin/build_apache_conf

To verify the include files, execute:

# /scripts/verify_vhost_includes

It will display the path of the .conf file you created. Restart the Apache service once

# /scripts/restartsrv httpd

This will ensure all the users use the server side php configuration file. If you wish to keep the php.ini elsewhere, just change the value of “suPHP_ConfigPath” and follow the above steps.

When PHP is not compiled with Mysql, you receive ‘Call to undefined function mysql_connect’ error message on your website

Fatal error: Call to undefined function mysql_connect()
 in filename.php on line xx

In order to fix the issue, install the “php-mysql” package using yum

# yum install php-mysql

Once installed, restart the httpd service

# service httpd restart

To verify if the package is installed properly, execute

# php -i | grep mysql

How to check Memory (RAM) usage in Linux OR different ways to check RAM usage in Linux?

Memory OR widely known as RAM is known to be one of the important component on the server which make sure the tasks performed on your server are processed fast enough. Higher the availibility of physical memory, more stable is your server during high resource usage processes.

Linux offer various tools to check Memory/RAM usage of your server such as free, top, sar, vmstat etc using which you can deside whether to optimize softwares to use less memory OR whether it’s time to upgrade memory on the server.

1) ‘free’ command: one of the easiest way to check the RAM usage:

free -m
will display physical memory as well as Swap

free -m -t
same as above but it will display the total of physical and swap memory at the bottom.

2) ‘top’ command: The top command displays the real time values of the running system and are continously updated (by default 3 seconds). The two rows “Mem and Swap” displays the total, used and free amount of RAM/Swap. Though the values displayed are in kbs and not human readable, it is just one another way to check the usage.

3) ‘sar’ command: is included in the ‘sysstat’ package and is not installed by default. To install ‘sysstat’ package, execute:

yum install sysstat

Once ‘sysstat’ package is installed, start the service

service sysstat start

sysstat package when installed, provider ‘sar’ command which collects system activity information and saves it in a file before displaying it on a standard output.

sar -r
displays Memory/Buffer/Swap information horizontally.

4) /proc/meminfo file: which displays everything about the RAM on your server.

cat /proc/meminfo

Related Links:

How to find out CPU utilization in Linux?

If the db4 packages (db4 and db4-devel) are missing on the server it results in “version.c:30:16: error: db.h” error message while installing any package. The error looks like:

version.c:30:16: error: db.h: No such file or directory
make: *** [version.o] Error 1

See if the db4 packages are installed

# rpm -qa | grep db4-devel
 db4-4.2.52-7.3.el4
 db4-devel-4.2.52-7.3.el4

If the above commands returns nothing, you have to install the db4 and db4-devel packages. Search the packages using yum and it should list both of them:

# yum search db4

It will list both the db4 and db4-devel packages

db4.x86_64
db4-devel.x86_64

Now, install them

# yum install db4.x86_64
# yum install db4-devel.x86_64