Occasionally you will have to troubleshoot server errors
and problems. Many of these occur when a quota has been exceeded, log files
have accumulated to fill a quota, or processes have hung.
Checking the Quota
Remember, when the quota hard limit is met, nothing can
write to the disk. E-mail is not accepted, logs are not written, installs do
not complete, and guestbooks and forms do not save to file. The quota has a
soft limit (which you may temporarily exceed) and a hard limit (which you may
never exceed), so you have time to fix the problem.
Note: If you edit files
while you are over quota, you run the risk of deleting your passwd file.
Checking the Log Files
When users report problems, first check the quota, and
then check the appropriate log files. Many times the error the end user is
reporting is an obscure client error. Log files will give more details on the
error.
It is helpful to use the tail
command on a particular log file while the user duplicates the error.
(Errors that users get while they are browsing your Web
site are recorded in the /www/logs/error_log
file.)
Checking Processes
If you are getting errors, use the top and ps
commands to check current processes. It is not uncommon to have a CGI not
closing properly, thereby using all of the VPS v2 Virtual Server's capacity. Occasionally the
popper (mail) process may hang when a user's connection is terminated
improperly. When checking top, look at the time a process has been running. If
it is idle and has been running for a long time, it may be hung and causing you
some problems. For example, an FTP process can hang if the connection to your
server disconnects improperly.
Contact Technical Support if all else fails. Technical
Support can give the details of what was done to solve the problem, and you can
keep that information for future use. Also check Enetrics Communications's Web site. The
Web site features a rich support library with hundreds of pages devoted to
supporting the VPS v2 Virtual Server.
Important Commands, Directories, and Files
The following table describes directories, files, and
commands used to maintain your
VPS v2 Virtual Server.
|
Name |
Type |
Description |
|
cat /dev/null > var/log/
maillog |
command |
A command you can use to clear /var/log/maillog |
|
cat /dev/null > var/log/
messages |
command |
A command you can use to clear /var/log/messages |
|
cron |
daemon |
Daemon to execute scheduled commands |
|
crontab –l
crontab –e
crontab -r |
cron
commands |
Displays cron’s copy in
memory
Edit cron
Remove cron |
|
du |
command |
Displays disk usage statistics; displays the file system
block usage for each file argument and for each directory in the file hierarchy
rooted in each directory argument. If no file is specified, the block usage
of the hierarchy rooted in the current directory is displayed. |
|
getback (filename) |
command |
Restores a file. |
|
ps |
command |
Displays a header line followed by lines containing information
about your processes that have controlling terminals. This information is
sorted by controlling terminal, then by process ID. Process status |
|
ps –ax | grep pop |
sample command |
Displays processes that are running POP |
|
ps –ax | grep imap |
sample command |
Displays processes that are running IMAP |
|
kill (PID number) |
command |
Kills a process |
|
rotatelogs |
commands |
Rotates Apache (Web) logs without having to kill the Web
server |
|
vinstall savelogs |
utility |
Deletes Apache (Web) logs |
|
/usr/local/etc/savelogs-nuke.conf |
file |
A configuration file for savelogs that you can create,
after which you run the savelogs command like this: |
|
/etc/syslog.conf |
file |
Determines what kinds of log messages go where. Each
message has a "facility" and a "priority" or "level”
Controls which log files are rotated and when |
|
savelogs –-config=/usr/local/etc/savelogs-nuke.conf |
command |
Deletes Apache (Web) logs |
|
tail -f |
command |
Prints the last 10 lines of a file. –f enables you to
follow the file as it grows. |
|
top
n
k |
command |
Displays server load, both the cumulative totals of the
physical machine, and totals of the VPS v2 Virtual Server: load average, number of processes
and their PIDs, CPU use in percentage, etc.
number of process
kill process |
|
/var/log/
messages |
file |
Contains log of ftp and other transactions |
|
/var/log/
maillog |
file |
Contains log of e-mail messages |
|
/www/logs/
access_log |
file |
Contains log of Web accesses |
|
/www/logs/
error_log |
file |
Contains log of Web access errors |
For More Information
For more information about the topics discussed in this
chapter, see the following pages on Our Web site.
Log Analysis - analog
Log Analysis -
http-analyze
Log Analysis - The Webalizer
Log Analysis - awstats
Log Analysis - Urchin
Log Analysis - Webtrends
