Howto on Body of Knowledge | João Malcata

Answering questions in interviews

Tue, 07 Feb 2023 14:58:00 +0000

Some quick tips on the recommended format of answers to interview questions.

Job interview preparation

Thu, 02 Feb 2023 17:29:00 +0000

Preparing for an interview can increase your self-confidence and reduce your risk, even if you never feel completely ready. Here are five key steps to help you get ready.

mirror/download a website

Mon, 21 Jan 2008 00:36:50 +0000

If you need for some reason to download a full website, wget is a nice tool to accomplish this. With “man wget” you can get a pretty good idea of all available features. I heard there is also a wget version for windows. Let us examine an example:

-m stands for mirroring
-k and -K convert the page with local links
-E to convert to an html suffix
–random-wait to add a random waiting period between requests

wget -m -E -k -K -w 1 --random-wait -o logfile https://website_uri/path

Disable directory browsing in apache

Mon, 21 Jan 2008 00:35:12 +0000

You can disable directory browsing at several levels like everything else. In order to do that:

Edit either the http.conf or a specific .conf file or the .htaccess file.
If exists, look for “Option Indexes”
Replace it or create a new line with “Options -Indexes”

WPA 1 on Ubuntu 7.10 Gutsy

Thu, 08 Nov 2007 03:00:05 +0000

After trying the gnome network configuration tool with little success, I tried the hardcore version, changing by hand the /etc/network/interfaces file again with little success. First search for your AP:

iwlist eth1 scanning

If you have a working wireless network adapter (eth1) and your AP in range, your configuration file should look something like this:

auto eth1
iface eth1 inet dhcp
wpa-driver wext
wpa-ssid SSID
wpa-ap-scan 1
wpa-proto WPA
wpa-pairwise TKIP
wpa-group TKIP
wpa-key-mgmt WPA-PSK
wpa-psk XXXXXXXXXXXXXXXXXXXXf4b3cff05d8ebf483435050268bxxxxxxxxxx

Your key for wpa-psk can be generated using:

redhat rpms for very old versions

Tue, 23 Oct 2007 17:14:36 +0000

You can find it here: rpmfind.net/linux/rpm2html/search.php?query=&submit=Search+…&system=&arch=

check the latest kernel version available

Wed, 22 Aug 2007 00:14:41 +0000

In order to check the latest kernel version available just do this:

finger @kernel.org

And get an output similar to:

[kernel.org]
The latest stable version of the Linux kernel is:           2.6.22.4
The latest prepatch for the stable Linux kernel tree is:    2.6.23-rc3
The latest snapshot for the stable Linux kernel tree is:    2.6.23-rc3-git4
The latest 2.4 version of the Linux kernel is:              2.4.35.1
The latest 2.2 version of the Linux kernel is:              2.2.26
The latest prepatch for the 2.2 Linux kernel tree is:       2.2.27-rc2
The latest -mm patch to the stable Linux kernels is:        2.6.23-rc2-mm2

mount windows share on a linux box

Mon, 18 Jun 2007 13:23:57 +0000

First install smbmount that should be on smbfs package, for Debian use something like:

sudo apt-get install smbfs

To try and access, create a new mounting point and connect:

sudo mount -t smbfs -o username=<user>,workgroup=<domain> //winserver/share1 /share /share1

To make it permanent add this line to your /etc/fstab as root:

//winserver/share1 /share/share1 smbfs credentials=/home/user/credentials,uid=user,gid=user,dmask=700,fmask=700 0 0

In order to avoid having passwords on your fstab create a file /home/user/credentials like this:

web stress test tool

Fri, 08 Jun 2007 19:53:29 +0000

Tired of “time wget”, apache has a simple stress tool “apache benchmark” that goes like this:


ab -kc 10 -t 10 -v 4 -A user:pass "https://uri/dir/file?param=x" > ab_result.txt

Check valid email addresses

Fri, 01 Jun 2007 12:16:15 +0000

Filter invalid email addresses using shell script:

Check for valid domain names

cat email_addr.txt | cut -d "@" -f 2 | sort -u| xargs -I {} host -t MX '{}' | grep "not found";

Check for email address RFC compliance

cat email_addr.txt | egrep "^[a-Z0-9,\!\#\$\%\&'\\*\+/=\?\^\\_\`\{\|\}\~\-]+(\.[a-Z0-9,\!\#\$\%\&'\\*\+/=\?\^\_\`\{\|\}\~\-]+)\*@[a-Z0-9-]+(\.[a-Z0-9-]+)\*\.([a-Z]{2,})$"

opacity bugs on Ubuntu with Beryl

Tue, 03 Apr 2007 18:07:42 +0000

If you are experiencing opacities issues with some windows just go to Beryl Settings Manager, pick Window Management and then check “Set Window Attribs by various criteria” selecting “Disable ARGB visual” add to the inclusion list an entry, example for Terminal Server Client:

c:rdesktop:1

Blank window on java applications under Beryl on Ubuntu

Sat, 31 Mar 2007 20:20:45 +0000

If you are getting a blank (grey) window with some java applications under Beryl that once you change Metacity works fine, just add the following line to your .bashrc and it should start working.

export AWT_TOOLKIT=MToolkit

post file request with curl

Tue, 06 Mar 2007 18:31:21 +0000

curl -d '@file.xml' https://website/path/file

using openssl to encrypt/decrypt content

Wed, 21 Feb 2007 18:55:38 +0000

Here you can find and sample on how to encrypt and decrypt content using OPENSSL. This sample goes with 3DES but it is valid for other chiphers. Notice the password will be requested to do the encryption.

Encoding foo.txt

openssl enc -des3 -in foo.txt -out foo.3des

Decoding foo.3des

openssl enc -d -des3 -in foo.3des -out bar.txt

bash shell shortcuts

Fri, 19 Jan 2007 13:51:00 +0000

____________CTRL Key Bound_____________
Ctrl + a - Jump to the start of the line
Ctrl + b - Move back a char
Ctrl + c - Terminate the command
Ctrl + d - Delete from under the cursor
Ctrl + e - Jump to the end of the line
Ctrl + f - Move forward a char
Ctrl + k - Delete to EOL
Ctrl + l - Clear the screen
Ctrl + r - Search the history backwards
Ctrl + R - Search the history backwards with multi occurrence
Ctrl + u - Delete backward from cursor
Ctrl + xx - Move between EOL and current cursor position
Ctrl + x @ - Show possible hostname completions
Ctrl + z - Suspend/ Stop the command\

easy ssh tunnel

Mon, 08 Jan 2007 16:55:49 +0000

Create a dynamic port forwarding socks proxy to a remote server via ssh:

ssh -D port bind_server -l bind_user

Access a remote service on a local lan behind a bind server via ssh forwarding:

ssh bind_address -l bind_user -L port:host:hostport

Vmware on linux with a NTFS file system

Fri, 10 Nov 2006 01:51:24 +0000

If you have a virtual machine running on NTFS, your virtual machine does not boot and you find errors in the log file like this one:

...
FILEIO: Unknown filesystem 0x65735546 for directory ...
...

Then insert this line in our .vmx file. Just don’t ask me why, it just works.

mainMem.useNamedFile=FALSE

Bash newbies tutorials

Thu, 09 Nov 2006 01:39:21 +0000

What is bash? and basic Commands

Scripting

Add links to quick launch programatically

Wed, 08 Nov 2006 13:14:30 +0000

Just copy the link to:

C:/Documents and Settings/username/Application Data/Microsoft/Internet Explorer/Quick Launch

Uhmm… Internet explorer….

useful Windows family administration tools

Thu, 26 Oct 2006 13:46:47 +0000

howto install cisco vpn client on Ubuntu

Thu, 26 Oct 2006 01:40:50 +0000

Getting ready to compile the code

sudo apt-get install build-essential linux-headers-`uname -r`

Get the lastest version from cisco and untar

tar zxvf vpnclient-linux-x86_64-4.8.00.0490-k9.tar.gz

Make (inside the vpnclient dir)
```
make
```
install vpn client
```
sudo ./vpn_install
```
Create a VPN profile with info like Host, authentication method…
```
sudo pico /etc/opt/cisco-vpnclient/Profiles/sample.pcf
```
Start the VPN Service
```
sudo /etc/init.d/vpnclient_init start
```

Import a given root certificate

sudo cisco_cert_mgr -R -op import -f root.cer

Import a given user certificate

wpa wlan on ubuntu

Tue, 24 Oct 2006 23:48:36 +0000

On Ubuntu (dapper at least) WEP is installed but not WPA (wi-fi protected access) a safer encription protocol. Wep can be cracked within minutes. To enable WPA you must:

Install wpasupplicant
```
sudo apt-get install wpasupplicant
```
Generate wpa passphrase
```
sudo wpa_passphrase ssid [passprase]
```

Add network info to /etc/supplicant.conf

network={
ssid="ssid"
scan_ssid=1 # only needed if your access point uses a hidden ssid
proto=WPA
key_mgmt=WPA-PSK
psk=123456a123456e34d67daef00eb5fab3ae228716e1e123456c004bc61dccc98c
}

Finally update network file /etc/network/interfaces

ntfs mounted with write permissions

Fri, 20 Oct 2006 09:07:39 +0000

On Ubuntu (and in general) ntfs mount with write permissons is still a big issue. Here is a simple cookbook for NTFS read/write:

Add the folowing line to your sources.list file

deb https://flomertens.keo.in/ubuntu/ dapper main

Add the repository key be able to download the packages

wget https://flomertens.keo.in/ubuntu/givre_key.asc -O- | sudo apt-key add -

sudo apt-get && sudo apt-get upgrade

Install the package
```
sudo apt-get install ntfs-3g
```
Add your ntfs partition

Generic audio e video play using Ubuntu (or GNOME...)

Thu, 19 Oct 2006 09:49:12 +0000

You can use synaptic or apt-get to install the packages mentioned in the following links: https://help.ubuntu.com/community/RestrictedFormats https://ubuntuguide.org/wiki/Dapper#How_to_install_Multimedia_Codecs

add a scheduled job with crontab

Sun, 15 Oct 2006 13:42:03 +0000

In order to add a scheduled job just call “crontab -e” and add entries to the crontab file. Take a look at this scheduled crontab examples:

0 0 * * *       ~/incremental_bck.sh    --midnight every day
0 0 * * 1-5    ~/send_happybirthday.sh  --midnight every weekday
0 0 1,15 * *   ~/full_backup.sh         --midnight on 1st and 15th days

Reset MySql root password

Tue, 10 Oct 2006 18:38:41 +0000

Stop mysqld and restart it with the –skip-grant-tables –user=root

shell> mysql -u root -e "UPDATE mysql.user SET Password=PASSWORD('**newpwd**') WHERE User='root';"
shell> mysql -u root -e "FLUSH PRIVILEGES;"

Replace â€œnewpwdâ€ with the actual root password that you want to use.

recommended firefox extensions

Fri, 22 Sep 2006 10:13:21 +0000

Here is a list of recommended firefox extensions:

Tab Mix Plus - enhances browsing capabilities, includes session manager;
NoScript - alows JavaScript for trusted domains with white list management;

Spam free solution for e-mail registration

Thu, 21 Sep 2006 06:24:39 +0000

This service www.mailinator.com allows you to have an instant mailbox for getting junk e-mail without entering your personal data.

basic shell commands

Wed, 20 Sep 2006 19:24:06 +0000

Shell

Concatenate & Compress (to from)

tar -cvzf filepath/filename.tar.gz filename

Extract multiple files (from to)

tar -xvzf filename.tar.gz

Copy files across systems(from to)

scp user@from-server:path/file user@to-server:path/file

Sort with count by column x

cut -d " " -f 2 raw.file | sort | uniq -c | sort -nr > ordered_by_freq_file

–

References

www.watsys.unh.edu/Darlene/TechToolsFiles/LammersUNIXDemo/UNIX_Intro.html

install vmware tools on Ubuntu

Wed, 20 Sep 2006 07:23:08 +0000

Install needed packages

sudo apt-get install gcc
sudo apt-get install linux-headers-$(uname -r)

Create vmware tools package

Use VMware window option VM -> Install VMware Tools to generate a virtual DVD-ROM with the package.
Uncompress & Untar VMwareTools-x.x.x-xxxxx.tar.gz

click the packge DVD-ROM and “extract to” Desktop the tar.gz file

Run vmware-install.pl

sudo Desktop/vmware-tools-distrib/vmware-install.pl

mysql easy backup and restore

Sun, 10 Sep 2006 20:02:06 +0000

In essence in order to fully backup and restore a MySql database server, you just need to use two commands mysqldump and mysql. For a “small databases” scenario you can find at the end a simple script to send the backup by e-mail. In conjunction with crontab you can almost name it a backup policy.

MySQL backup>

mysqldump -u <user> -p <passwd> --all-databases > <backup file>

MySQL restore>

mysql -u <user> -p <passwd> < <backup file>
mysql --execute "update mysql.user set host='old' where host='host';"

Backup script example

#!/bin/bash
# This script runs nightly to back a MySQL database to a e-mail account
DATE1=`date +%D`
DATE2=`date +%Y%m%d%H%M`
# The email address that receives backups
ADDRESS="alias@domain"
# Local temp directory
BACKUPDIR="/tmp"
# MySQL username and password
MYSQLUSER="user"
MYSQLPASS="pass"
# MySQL database to backup (or --all-databases to backup everything)
DATABASE="--all-databases"
# Name of backup file
FILENAME="mysql\_backup"
# Change to the backup directory
cd $BACKUPDIR
# Dump the MySQL databases to a plaintext file
mysqldump -u $MYSQLUSER -p $MYSQLPASS $DATABASE > $FILENAME\_$DATE2
# Package (tar) and compress (gzip) the plaintext MySQL dump
tar czf $FILENAME\_$DATE2.tar.gz $FILENAME\_$DATE2
# Mail the resulting archive to our Gmail account
date | mutt -s "$FILENAME ($DATE1)" -a $FILENAME\_$DATE2.tar.gz $ADDRESS

thanks to Bruno Rodrigues

add / remove registry entries

Sun, 10 Sep 2006 18:46:45 +0000

In order to import registry changes use this command on the following .reg file examples.

regedit /S <reg file>

Add/update key and value

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\ExampleKey]
"StringValue"="example"

Remove key (including all values)

Windows Registry Editor Version 5.00
[-HKEY_CURRENT_USER\ExampleKeyToRemove]

Remove value

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\ExampleKey]
"ExampleStringValue"=-

Toolbar on XP taskbar hack

Sun, 10 Sep 2006 18:26:31 +0000

Due to some sort of domain policies you might be unable to have toolbars on the XP taskbar.

Create a batch file and add it to the startup scritps with the following text:

regedit /S "<path>\hacktoolbar.reg"

Create a .reg file hacktoolbar.reg:


Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoToolbarCustomize"=dword:00000000
"NoBandCustomize"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoToolbarsOnTaskbar"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoSaveSettings"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoActiveDesktop"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"ClassicShell"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoCloseDragDropBands"=dword:00000000

[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer]
"NoMovingBands"=dword:00000000

cygwin a windows saviour

Fri, 08 Sep 2006 12:54:14 +0000

If you “have” to use Windows, are able to install software but lack disk access cygwin is the answer to your prayers. Use the setup file everytime you want to install or add packages.

Nice cygwin configuration

Admin - cygrunsrv shutdown
Archive - unzip
Base - alternatives ash base-files base-passwd bash coreutils cygwin cygwin-doc diffutils editrights findutils gawk gdbm grep gzip libgdbm libgdbm-devel libgdbm3 libgdbm4 libncurses5 libncurses6 libncurses7 libncurses8 libreadline4 libreadline5 libreadline6 login man ncurses run sed tar termcap terminfo which zlib
Database - libdb4.1 libdb4.2 libdb4.3
Devel - expat gettext ioperm libiconv mktemp pcre ruby
Doc - cygwin-doc expat man texinfo
Editors - joe
Interpreters - expat gawk perl ruby
Libs - crypt expat fontconfig freetype2 gettext ioperm libXft libXft1 libXft2 libbz2\_1 libcharset1 libfontconfig1 libfreetype26 libiconv2 libintl libintl1 libintl2 libintl3 libncurses5 libncurses6 libncurses7 libncurses8 libpcre0 libpopt0 libreadline6 ncurses openssl openssl097 tcltk termcap zlib
Net - ncftp netcat openssh openssl openssl097 rsync
Perl - perl
Shells - ash bash chere rxvt
System - chere ioperm man ping util-linux
Text - expat groff less texinfo util-linux
Utils - bzip2 chere cygutils e2fsprogs pcre util-linux
Web - wget
X11 - X-startup-scripts xorg-x11-base xorg-x11-bin xorg-x11-bin-dlls xorg-x11-bin-lndir xorg-x11-etc xorg-x11-f100 xorg-x11-fenc xorg-x11-fnts xorg-x11-libs-data xorg-x11-nest xorg-x11-xwin xterm
**cygwin friendly shell**

C:\cygwin\bin\rxvt.exe -fn "Lucida Console-11" -bg black -fg white
-ls -st -sr -sl 1000 -C -e /usr/bin/bash --login

Subversion cookbook installation

Fri, 25 Aug 2006 18:58:29 +0000

This is a cookbook for a SubVersion (aka svn) installation on debian and apache2 with LDAP integration authentication.

Install subversion
```
apt-get install subversion
```

Configure subversion

mkdir /var/lib/svn
svnadmin create /var/lib/svn/repos
chown www-data:www-data /var/lib/svn/repos/ -R

Install Apache2
```
apt-get install apache2
```

Set apache2 modules

apt-get install libapache-mod-ldap libapache-auth-ldap libapache2-svn

If needed enable modules

a2enmod ldap
a2enmod auth_ldap

Setup Apache2 website
- Create folder
```
mkdir /var/www/svnwebsite
```
- Create website configuration file usually in /etc/apache2/sites-available

Multiple web sites installation on wordpress

Wed, 23 Aug 2006 23:10:07 +0000

Here are the basic steps to install another wordpress weblog on a multiple web sites infrastructure over a single apache2 on debian.