Linux VPS - Cautions and Warnings
Following are cautions and warnings regarding the following Linux VPS 3.0 features:
Linux VPS and Java Applications
Many Java applications consume significant CPU and memory resources and may not be appropriate for use on a VPS. Java applications
on a VPS should be restricted for use only on websites with a low expected workload. In addition, some larger Java applications
may not be suitable for use on a VPS even with low workloads.
There are a wide range of Java-based applications. Some are designed to handle multiple services and others focus on a smaller
range of services. As an example, Zimbra (http://www.zimbra.com/) is open-source server and client software used to process
email, group calendaring, and contacts. In addition, the software supports Web document management and authoring. The software
offers a wide range of services, some of which duplicate applications included with the default configuration of Linux VPS Pro
Plus. The software offers these services by drawing on Java and its own, duplicate installation of Tomcat. These factors make
the software better suited to a more powerful, dedicated server offering such as MPS.
Alternatively, JSP Wiki (http://www.jspwiki.org/) uses standard Java 2 Platform, Enterprise Edition (J2EE) components such as
Java, servlets, and JSP. The software enables collaborative authoring for Web sites. The software enables visitors to comment
upon, add to, or remove from Web page (or wiki) content. The open-source software focuses on providing a singular, unique
service. It does this by utilizing the Java components which are part of the default configuration of Linux VPs Pro Plus. And
the software does not duplicate services which are also supported by Linux VPS, such as email.
JSP Wiki is an example of a Java-based application which is well-suited to Linux VPS Pro Plus only when put under low to moderate
workloads. Results will vary by application, but JSPWiki running on a Linux VPS Pro Plus will potentially handle up to tens
of thousands of wiki page views per day. Should hundreds of thousands of wiki page views per day be required, upgrading to
a dedicated server such as a Managed Private Server (MPS) is recommended.
AlpineWeb strongly recommends sufficient performance testing of your Java application on a Linux VPS before relying on it for
critical business needs. AlpineWeb also recommends building contingency plans in case your Java application does not perform as
expected; alternative solutions may include:
- Extensive optimization of the Java application.
- Moving the Java application to a dedicated server, such as the MPS.
- Implementing an alternative solution to using Java (For example: moving away from Java to an optimized C program.)
For details of Linux VPS plan resource allocations and recommended usage, please refer to the Linux VPS 3.0 Technical Overview.
Resume Logging and Access Log Files
After you save system logs by running a savelog command for /var/log files, you can expect that savelog files are created and
original system log files are deleted. In order to access original log files and to resume logging, you must restart the syslog
daemon by issuing a signal hang up (sighup) command, as follows:
# kill -hup syslog
In addition, there are variations of the signal hang up command and you can issue a restart command such as # service syslog
restart. For more information about these commands and other restart and/or signal hang up commands, refer to the inline RHEL
command reference (man pages).
Assign Provisioned IP Addresses Only
Do not specify a different IP address than those assigned to your account at the time of provisioning. If you do, your account
will not function. This is true of any IP address, even those you might see displayed as an unused IP address for the subnet of
your account. Your account will not function with any other IP addresses and you will not be able to see information about any
aspect of the data traffic associated with any other IP addresses.
The Red Hat Enterprise Linux (RHEL) operating system supports a standard, UNIX/Linux command which enables you to see the status
of network interfaces for your account. Use the command for diagnostic and configuration tasks. For example, if you issue
ifconfig command without any additional argument, all of the currently active interfaces are displayed. If you issue the
command with the additional argument of -a, all of the interfaces, including inactive ones are displayed. Beyond the simple
display of interfaces, the command includes additional arguments which enable you to specify an IP address for each network
interface.
If you do specify another address in error, the remedy is to log into your account as root and use the ifconfig command to
specify a correct IP address. Since your account does support multiple IP addresses, you can specify any of the IP addresses
you own and have provisioned as a part of your account.
For more details about the ifconfig command, refer to the RHEL operating system man pages.
File System Utilities and Your Online Back up Files
During the time period the file system utility is backing up your account's files and directories, it is possible for any user
with root access to your account to inadvertently alter or delete those files and directories.
System administrators use a file system utility such as cloneDir to duplicate directories of files (or backup files). In
addition to creating backup files, the utility also preserves timestamps and reproduces ownership and permission levels. By
performing all of these tasks, the utility builds a reliable mirror of the hierarchy of files and subdirectories.
In general, your account's backup files are classified as read-only. However, during the backup process, the utility might
change the mount to read-write. And, during that time, any user with root access to your account can inadvertently alter or
delete the online backup files.
The utility replaces the backup files the following day when the utility runs again. However, once altered or deleted, the
backup files are no longer accurate until the next time the utility runs. The remedy for this concern is to strictly limit the
users you provide root access.
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