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Linux / UNIX: Encrypt Backup Tape Using Tar & OpenSSL

How do I make sure only authorized person access my backups stored on the tape drives (DAT, DLT, LTO-4 etc) under Linux or UNIX operating systems? How do I backup /array22/vol4/home/ to /dev/rmt/5mn or /dev/st0 in encrypted mode?
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How To Use awk In Bash Scripting

How do I use awk pattern scanning and processing language under bash scripts? Can you provide a few examples?
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Debian / Ubuntu MySQL Error Log File Location

Can you tell me the location of for the MySQL error log file under Debian or Ubuntu Linux? How do I view error log file?
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xargs: How To Control and Use Command Line Arguments

I am trying to use xargs command using shell pipes and not able to understand how to control and use command line arguments. For example I’d like to find out all *.c file located in 100s of sub-directories and move them to another directory called ~/old.src. How do I use command line args with xargs to achieve the same?
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Linux Find Large Files

Q. I’d like to save disk space for my FreeBSD 7 ISP server. We run webserver, nameserver from various jails under powerful HP RAID 10 server. How do I export /usr/ports from host to each jail hosted on /jail/ volume such as /jail/www, /jail/ns, /jail/sql etc?
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Shell: How To Remove Duplicate Text Lines

Q. I need to sort data from a log file but there are too many duplicate lines. How do I remove all duplicate lines from a text file under GNU/Linux?
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Linux: Find my IP address using Perl at a shell prompt

Q. How do I find out my IP address assigned to eth0 or ra0 interface using perl?

A. If you need to know the IP address of the UNIX / Linux machine you are running on, use the following perl one liner. Perl don’t have any inbuilt facility but combination of ifconfig command ans shell pipes you can craft something as follows to display your system IP address:

Find my IP address using Perl One liner and shell pipes

Type the following command at a shell prompt:

ifconfig -a | perl -ne 'if ( m/^\s*inet (?:addr:)?([\d.]+).*?cast/ ) { print qq($1\n); exit 0; }'

Linux: Display rpm package architecture

Q. I’m using CentOS on 64 bit Linux. How do I find out rpm package architecture before installation such as i386 or x86_64 bit?

A. Almost each rpm package has i386 or x86_64 added to file extension. However some time you may see filename such as file-version.rpm. You can list all installed rpm packages with rpm -qa command but it will not display architecture. You can run following command to display rpm package architecture:
rpm -qa --qf "%{n}-%{arch}\n"
Ouput:

filesystem-x86_64
comps-extras-noarch
gnome-mime-data-x86_64
glibc-x86_64
atk-x86_64
libICE-x86_64
db4-x86_64
elfutils-libelf-x86_64
ncurses-x86_64
libsepol-x86_64
libcap-x86_64
sqlite-x86_64
pcre-x86_64
gdbm-x86_64
libsepol-i386
libXdmcp-x86_64
db4-i386
iptables-x86_64
libXrender-x86_64
libXi-x86_64
xorg-x11-font-utils-x86_64
slang-x86_64
libXpm-x86_64
startup-notification-x86_64
gzip-x86_64
libIDL-x86_64
libXau-i386
wireless-tools-x86_64
libvorbis-x86_64

Another option is to use following command to display detailed information about package:
rpm -qi {package-name}
If you wish to display package version along with architecture, enter:
rpm -qa --qf "%{n}-%{v}-%{r}.%{arch}\n" | less
Run rpm command to print a list of all of the tags it knows about when it is invoked with the –querytags argument.
rpm --querytags | less

Bash Script Replace Empty Spaces String

How do I remove all spaces from string using shell scripts? I’ve var=”This is a test”, and I’d like to remove all spaces.
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