Archive for the ‘Basics’ Category
Get a list of all virtual hosts which are defined in all apache configuration files
Have you ever searched where the virtual host of a website is defined in the apache config files? There is a handy option of the apache2ctl script which might help then. When you run the command:
apache2ctl -S
on the shell, you will get a list of all virtual hosts and default servers incl. the line number where it is defined. Example:
~# apache2ctl -S VirtualHost configuration: wildcard NameVirtualHosts and _default_ servers: *:8080 is a NameVirtualHost default server ispconfig.local (/etc/apache2/sites-enabled/000-ispconfig.vhost:10) port 8080 namevhost ispconfig.local (/etc/apache2/sites-enabled/000-ispconfig.vhost:10) *:8081 is a NameVirtualHost default server ispconfig.local (/etc/apache2/sites-enabled/000-apps.vhost:10) port 8081 namevhost ispconfig.local (/etc/apache2/sites-enabled/000-apps.vhost:10) *:80 is a NameVirtualHost default server ispconfig.local (/etc/apache2/sites-enabled/000-default:1) port 80 namevhost ispconfig.local (/etc/apache2/sites-enabled/000-default:1) port 80 namevhost example.com (/etc/apache2/sites-enabled/example.com.vhost:7) Syntax OK
Thanks to Planetfox for this tipp.
How to remove old java versions from Windows
When you install the latest java runtime enviroment, it gets installed beside your existing java installation. With every java update, more space is used on the harddisk. To remove old java versions, there is a tool named JavaRa which can be downloaded here:
https://sourceforge.net/projects/javara/files/javara/JavaRa/JavaRa.zip/download
Unpack the JavaRa.zip file and double click on the JavaRa.exe to start JavaRa. Select the language:
and click on “Remove older versions”.
How to convert RPM software packages to Debian (.deb)
Maybe you had this problem already: you use Debian or Ubuntu Linux and a software package that you like to install is only available in RPM format. The solution is a handy tool called alien, which converts .rpm files to .deb. Installing alien:
apt-get install alien
Converting a rpm package to debian format:
alien --to-deb /tmp/mysoftwarefile.rpm
Conversions from .deb to rpm are also possible:
alien --to-rpm /tmp/mysoftwarefile.deb
Rerun the last command with sudo on the Linux shell
Have you ever executed a command on the shell and noticed the that you had to run it with sudo? Instead of typing the command again with “sudo” in front of it, just run:
sudo !!
which will execute the command that was run before with sudo. Thanks to Planetfox for this tipp.
How to kill processes in “D” state in Linux?
If a process is shown with process state “D” in tools like ps or top, then its a zombie process. Example:
ps axl | grep D F UID PID PPID PRI NI VSZ RSS WCHAN STAT TTY TIME COMMAND 4 104 2579 9109 20 0 5024 2116 refrig D ? 0:00 cleanup -z -t unix -u -c
Zombie processes can not be killed with the normal commands like “kill -9 PID”, you will have to reboot the system to kill them.
How to use apt-file to find which .deb package contains a specific file
Sometimes you need to know which debian package contains a specific file e.g. because you deleted a system file accidently or you try to install a new software that requires this file. The apt package management utility which is used in Debian and Ubuntu comes with a handy tool called apt-file which allows a saerch for filenames in the package database.
Install apt-file
apt-get install apt-file
Update the apt-file database
apt-file update
Search for a specific file name, e.g. “lcrypto”
apt-file search /bin/bash
apt-file search /bin/bash bash: /bin/bash bash: /usr/bin/bashbug bash-minimal: /bin/bash-minimal bash-static: /bin/bash-static bashdb: /usr/bin/bashdb mybashburn: /usr/bin/bashburn
Test the phising filter of your web browser
If you like to test if the phising filter of your webbrowser works, open the following URL of the mozilla test page in the browser:
You should get a result page that looks similar to this one if you use the Mozilla Firefox browser:
Optimize MySQL performance with mysqltuner
The following tutorial describes the steps to optimize the performance of a MySQL database with the mysqltuner script.
Login to your server on the shell, then execute the following commands:
Download the mysqltuner script:
cd /usr/local/bin wget http://mysqltuner.pl/mysqltuner.pl chmod +x mysqltuner.pl
Run mysqltuner
/usr/local/bin/mysqltuner.pl
Then enter root as username and the mysql root password.
You will get a output similar to this:
root@v221:/usr/local/bin# /usr/local/bin/mysqltuner.pl
>> MySQLTuner 1.0.1 - Major Hayden <major@mhtx.net> >> Bug reports, feature requests, and downloads at http://mysqltuner.com/ >> Run with '--help' for additional options and output filtering Please enter your MySQL administrative login: root Please enter your MySQL administrative password:
-------- General Statistics -------------------------------------------------- [--] Skipped version check for MySQLTuner script [OK] Currently running supported MySQL version 5.0.51a-24+lenny2 [!!] Switch to 64-bit OS - MySQL cannot currently use all of your RAM
-------- Storage Engine Statistics ------------------------------------------- [--] Status: +Archive -BDB -Federated +InnoDB -ISAM -NDBCluster [--] Data in MyISAM tables: 26M (Tables: 215) [!!] InnoDB is enabled but isn't being used [!!] Total fragmented tables: 33
-------- Performance Metrics ------------------------------------------------- [--] Up for: 96d 23h 3m 41s (10M q [1.239 qps], 686K conn, TX: 701M, RX: 1B) [--] Reads / Writes: 44% / 56% [--] Total buffers: 58.0M global + 2.6M per thread (100 max threads) [OK] Maximum possible memory usage: 320.5M (12% of installed RAM) [OK] Slow queries: 0% (20/10M) [OK] Highest usage of available connections: 33% (33/100) [OK] Key buffer size / total MyISAM indexes: 16.0M/8.5M [OK] Key buffer hit rate: 99.9% (57M cached / 30K reads) [OK] Query cache efficiency: 78.6% (5M cached / 6M selects) [!!] Query cache prunes per day: 483 [OK] Sorts requiring temporary tables: 0% (0 temp sorts / 408K sorts) [!!] Temporary tables created on disk: 36% (269K on disk / 745K total) [OK] Thread cache hit rate: 99% (427 created / 686K connections) [!!] Table cache hit rate: 2% (64 open / 3K opened) [OK] Open file limit used: 11% (120/1K) [OK] Table locks acquired immediately: 99% (3M immediate / 3M locks)
-------- Recommendations ----------------------------------------------------- General recommendations: Add skip-innodb to MySQL configuration to disable InnoDB Run OPTIMIZE TABLE to defragment tables for better performance Enable the slow query log to troubleshoot bad queries When making adjustments, make tmp_table_size/max_heap_table_size equal Reduce your SELECT DISTINCT queries without LIMIT clauses Increase table_cache gradually to avoid file descriptor limits Variables to adjust: query_cache_size (> 16M) tmp_table_size (> 32M) max_heap_table_size (> 16M) table_cache (> 64)
The script recommends to adjust or add the following variables in the mysql my.cnf file. The location of my.cnf is normally /etc/my.cnf or /etc/mysql/my.cnf depending on the Linux distribution that is installed on your server.
Open the my.cnf file:
vi /etc/mysql/my.cnf
and increase or set the variables in the [mysqld] section of the file. Mine looks now like this:
[mysqld] # # * Basic Settings # user = mysql pid-file = /var/run/mysqld/mysqld.pid socket = /var/run/mysqld/mysqld.sock port = 3306 basedir = /usr datadir = /var/lib/mysql tmpdir = /tmp language = /usr/share/mysql/english skip-external-locking # # Instead of skip-networking the default is now to listen only on # localhost which is more compatible and is not less secure. bind-address = 127.0.0.1 # # * Fine Tuning # key_buffer = 16M max_allowed_packet = 16M thread_stack = 128K thread_cache_size = 8 # This replaces the startup script and checks MyISAM tables if needed # the first time they are touched myisam-recover = BACKUP #max_connections = 100 table_cache = 128 #thread_concurrency = 10 # # * Query Cache Configuration # query_cache_limit = 1M
query_cache_size = 32M tmp_table_sizee = 64M max_heap_table_sizee = 32M
Then save the file and restart mysql. After a few hours, rerun mysqltuner and check again if the values are fine now or if the have to be increased to a higher value.
Manage the postfix mailqueue with postsuper, postqueue und mailq
Postfix provides with postsuper, postqueue and mailq some shell utilitys to manage the mailqueue.
Here are some examples for common tasks:
List all messages that are in the mailqueue
postqueue -p
The output looks like this:
root@server:/# postqueue -p -Queue ID- --Size-- ----Arrival Time---- -Sender/Recipient------- 501CA23B43DB 2182 Thu Dec 3 14:24:39 test@yourdomain.com (Host or domain name not found. Name service error for name=otherdomain.com type=MX: Host not found, try again) info@otherdomain.com -- 8 Kbytes in 1 Requests. <strong>Delete a message by message ID</strong> <p class="command">postsuper -d MessageID
replace MessageID with the ID of the message, e.g. 501CA23B43DB
root@server:/# postsuper -d 501CA23B43DB postsuper: 501CA23B43DB: removed postsuper: Deleted: 1 message <strong>Remove emails by sender</strong> <p class="command">mailq | tail +2 | awk 'BEGIN { RS = "" } # $7=sender, $8=recipient1, $9=recipient2 { if ($7 == "info@otherdomain.com" && $9 == "") print $1 } ' | tr -d '*!' | postsuper -d - replace "info@otherdomain.com" with the sender email address. <strong>Remove emails by recipient</strong> <p class="command">mailq | tail +2 | awk 'BEGIN { RS = "" } # $7=sender, $8=recipient1, $9=recipient2 { if ($8 == "you@yourdomain.com" && $9 == "") print $1 } ' | tr -d '*!' | postsuper -d - replace you@yourdomain.com with the recipient email address. <strong>Remove emails by sender hostname</strong> <p class="command">mailq | grep senderhostname | awk ‘{ print $1′} | postsuper -d -
replace the word “senderhostname” with the hostname of the email sender.
If your server has very high load and you want to temporarily move all message from the incoming queue to the hold queue, use the command:
postsuper -h ALL
to move the messages back to the incoming queue, use the command:
postsuper -r ALL
Instead of the word “ALL” you can also provide a specific message ID to move only one message to or from the hold queue. Message in the hold queue will not processed by postfix until they were requeued with postsuper -r.
Find the .deb package that contains a specific file on Ubuntu or Debian Linux
Sometimes you need to know to which debian or ubuntu package a specific file belongs, e.g. because you deleted a system file and want to reinstall it. There is a handy utility called apt-file which searches for a filename in all debian packages.
Installation
apt-get install apt-file
Usage example
search for the file /etc/sysctl.conf
apt-file search /etc/sysctl.conf
result:
apt-file search /etc/sysctl.conf
procps: /etc/sysctl.conf
mypc:~#
Now we see that the file is part of the debian / ubuntu package with the name “procps”.