Difference between revisions of "Quick Notes"

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== Samsung Vibrant/Galaxy S ==
== Samsung Vibrant/Galaxy S ==
* LBS/GPS Test Mode: *#*#1472365#*#* SEND
* LBS/GPS Test Mode: *#*#1472365#*#* SEND
== LLDP/CDP Discovery with tcpdump ==
tcpdump -v -s 1500 -i eth0 'ether[20:2] == 0x2000]'
tcpdump -v -s 1500 '(ether[12:2]=0x88cc or ether[20:2]=0x2000'

Latest revision as of 07:46, 23 September 2015

This page is to list all of those quick, often one-line, commands or hints that help during the course of system administration.





  • Network Overhead Guide
  • To capture packets for wireshark/ethereal, run tcpdump as: tcpdump -i <interface> -s 1500 -w <some-file>

MediaWiki Notes

This section is for all the stuff you can do or need to do with Media Wiki that isn't found in an easy location.


You can edit the links under navigation, etc, on the left of the page by going to a special page in MediaWiki. <host>/wiki/index.php/MediaWiki:Sidebar will take you there. You can see the SCN side bar at MediaWiki:Sidebar.


Command Line Foo

  • Interface statisctics without iftop from ports: systat -if

with csh/tcsh, |& pipes both stdout and stderr. same effect as 2>&1 | in bourne-based shells (or /bin/sh)

Make this command an alias to tree in your .<shell>rc and get that ol' DOS-style tree:

find . -print | sed -e 's;[^/]*/;|____;g;s;____|; |;g'

Here's a nice command to use in conjunction with GeekTool for current weather conditions on your desktop:

curl --silent "http://xml.weather.yahoo.com/forecastrss?p=YOURCITYCODE&u=c" | grep -E '(Current Conditions:|C<BR)' | sed -e 's/Current Conditions://' -e 's/<br \/>//' -e 's/<b>//' -e 's/<\/b>//' -e 's/<BR \/>//' -e 's/<description>//' -e 's/<\/description>//'

Note: change YOURCITYCODE with your zip code.

iPhone Notes

Windows Notes




Postfix How-To


Link sudo to /usr/bin/sudo

# ln -s /usr/local/bin/sudo /usr/bin/sudo


  • No Scroll Tabs: goto about:config, set browser.tabs.tabMinWidth=1
  • Close on Tab: goto about:config, set browser.tabs.closeButtons=1


  • Postgres does not authenticate users as MySQL, and doesn't offer a shell.
  • When connecting to Postgres dbs, you must specify the db, otherwise a db names as the role will be assumed.

Basic Commands

  • psql -l (dash el): list databases
  • pg_dumpall: dump all dbs to stdout
    • gzipped use: pg_dumpall | gzip -c > all.dbs.out.gz
    • restore: gzcat all.dbs.out.gz | psql -f - postgres

MySQL Stuff

Command/Query Examples

Description Command Notes
Forcibly change a user's password. SET PASSWORD FOR user=PASSWORD('password');
Add New Database User GRANT ALL PRIVILEGES ON db.table to 'user'@'host' IDENTIFIED BY 'password'; You can use a % to denote ANY host. The percent (%) purposely excludes localhost, however.
Copy rows from one table to another. INSERT INTO foo SELECT * FROM bar; copies records from table bar into table foo.
action based on time interval SELECT FROM foo WHERE DATE(field) < (YYYYMMDD - INTERVAL nnn unit) Where unit = DAY/YEAR/MONTH - one of those, will select based on records older than the interval.
Flush all queries from the cache. FLUSH QUERY CACHE

This command can be used to dump all databases on the current system to another system, piping the content through an SSH session:

mysqldump -u USERNAME -pPASSWORD --opt --compress --all-databases | ssh REMOTEHOST "cat - | mysql -u USERNAME -pPASSWORD"


Apple Remote Desktop 3.1

This is just a place-holder.

GNU Screen

A nice .screenrc config file:
This config works well on both light and dark colored backgrounds.

startup_message off
shelltitle ''
defmonitor on
vbell off
hardstatus on
hardstatus alwayslastline
hardstatus string '%{= bW}%-Lw%{= rW}%50>%n%f %t%{= bW}%+Lw%< %-= %{..Y}%m/%d %c:%s%{-}'

Here's another .screenrc config, from Jeremy O'Brien (piroko):
This config works well on dark colored backgrounds.

shelltitle ''
startup_message off
vbell off
defmonitor on
monitor on
caption always "%{= kw}> %{y}%?%-Lw%?%{w}(%{R}%n*%t%?(%u)%?%{w})%{y}%?%+Lw%?%?%=%{w} [ %{.c}%M %d%{y}%0c:%s%{w} ]"

Screen after su

sudo su - <user>
script /dev/null
screen (or screen -r)



Function Code Example Description
foreach foreach ($array as $key => $value) { code }

Example for output files with support for multipart downloading:

                                if (isset($_SERVER['HTTP_RANGE'])){
                                        list($a, $range) = explode('=', $_SERVER['HTTP_RANGE'], 2);
                                        list($range) = explode(',', $range, 2);
                                        list($range, $rangeEnd) = explode('-', $range);

                                        $range = intval($range);

                                        if (!$rangeEnd){
                                                $rangeEnd = $fileSize -1;
                                        } else {
                                                $rangeEnd = intval($rangeEnd);
                                        $newLength = $rangeEnd - $range + 1;

                                        // Send Headers
                                        header("Content-Type: applicatoin/zip");
                                        header("Content-Length: $size");
                                        header("Content-Range: bytes " . $range - $rangeEnd / $size);
                                } else {
                                        $newLength = $size;
                                        header('Content-Length: ' . $size);


  • [1] - good how to for screen + irssi

RegEx (Regular Expressions)

REGEX What it does.
/^$|^\d{5}(-?\d{4})?$|^[ABCEGHJKLMNPRSTVWXYZ]\d[ABCEGHJKLMNPRSTVWXYZ](\s?)\d[ABCEGHJKLMNPRSTVWXYZ]\d/i Validates for blank string, US zipcode (either 5 digit or 5+4, and Canadian postal codes (with or without a space).

Samsung Vibrant/Galaxy S

  • LBS/GPS Test Mode: *#*#1472365#*#* SEND

LLDP/CDP Discovery with tcpdump

CDP: tcpdump -v -s 1500 -i eth0 'ether[20:2] == 0x2000]'

LLDP: tcpdump -v -s 1500 '(ether[12:2]=0x88cc or ether[20:2]=0x2000'