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linux command

Q. I see [ command in /usr/bin directory. What is the /usr/bin/[ command used for?
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HowTo: Find Out Hard Disk Specs / Details on Linux

Can you tell me a Linux command to find out information about my hard disk such as description, product name, bus type, size, and cache memory size under Linux operating systems using command line options?
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Squid Proxy Sever View logs / log files

Q. How do I view squid proxy server log files under CentOS Linux server 5.0?

A. squid is a high-performance proxy caching server for web clients, supporting FTP, gopher, and HTTP data objects. Unlike traditional caching software, squid handles all requests in a single, non-blocking, I/O-driven process.

/var/log/squid/ log file directory

The logs are a valuable source of information about Squid workloads and performance. The logs record not only access information, but also system configuration errors and resource consumption (eg, memory, disk space). There are several log file maintained by Squid. Some have to be explicitely activated during compile time, others can safely be deactivated during.

  • /var/log/squid/access.log : Most log file analysis program are based on the entries in access.log. You can use this file to find out who is using squid server and what they are doing etc
  • /var/log/squid/cache.log : The cache.log file contains the debug and error messages that Squid generates. If you start your Squid using the default RunCache script, or start it with the -s command line option, a copy of certain messages will go into your syslog facilities. It is a matter of personal preferences to use a separate file for the squid log data.
  • /var/log/squid/store.log : The store.log file covers the objects currently kept on disk or removed ones. As a kind of transaction log it is ususally used for debugging purposes. A definitive statement, whether an object resides on your disks is only possible after analysing the complete log file. The release (deletion) of an object may be logged at a later time than the swap out (save to disk).

How do I view Squid Log files / logs?

You can use standard UNIX / Linux command such as grep / tail to view log files. You must login as root or sudo command to view log files.

Display log files in real time

Use tail command as follows:
# tail -f /var/log/squid/access.log
OR
$ sudo tail -f /var/log/squid/access.log

Search log files

Use grep command as follows:
grep 'string-to-search' /var/log/squid/access.log

View log files

Finally you can use text editor such as vi to view log files:
# vi /var/log/squid/access.log

Q. Sometime I type command and accidentally hit the [ENTER] key and immeditly realized that it was wrong command. How do I stop process assuming that process is not going in background? For example
cp /path/* /wrong/path

Stop or terminate Linux command process with CTRL + C

A. To stop process hit CTRL + C, for example, you entered:
$ cp -r /path/* /wrong/path

To stop the command hit CTRL+C and retype the command:
$ cp -r /path/* /correct/path