Locating a Preconfigured “ls” Alias in CentOS Using grep

Linux distributions sometimes configure “ll” (lowercase L’s) as an alias to “ls -l”. Debian based OS’s typically do this from the users ~/.bashrc file. This is not the case with Red Hat/CentOS based OS’s. I couldn’t remember where CentOS set the alias and I needed to locate it. As a non-root user, this proved to be a little more challenging than I first expected. Yes, I could look it up on the web but I decided to make an exercise out of it and it was more challenging than it would first seem.

grep -riE "alias ?ll" /etc/ 2> /dev/null

I’m sure there are other ways to it but this worked. In short. I knew I needed to search for “ll” in /etc, but “ll” is also common in many words. Also, I’m running as a normal user so I wanted to avoid “Permission Denied” and other errors that cluttered the search.

Note the the following also returns the same:

 grep -riE "alias ?ll" /etc/ 2>&1 | grep -v "Permission" 

Make a bootable ISO from an install CD/DVD in Linux

It’s been a while since I last did this but you never know when you might need it.  When you see a “dd” command, you better make sure you know what you are doing.  In other words, don’t type this just as you see it!

Identify where CD/DVD is mounted:


Unmount the CD/DVD:

umount /dev/sr0

Copy data from CD/DVD to ISO file:

dd if/dev/sr0 of=~/image.iso

Or use dcfldd if you prefer:

dcfldd if/dev/sr0 of=~/image.iso

Combine multiple PDF files into a single PDF file

This is one of the oldest entries in my offline notes.  I used it quite a bit years ago.  Simply said, take several .pdf files and combine them into one file.

As always boys and girls – “man gs” in the terminal before you do this.*

gs -dBATCH -dNOPAUSE -q -sDEVICE=pdfwrite -sOutputFile=final.pdf file1.pdf file2.pdf file3.pdf


*As a side note:  some of the options in the above command are not in the man page on my Debian 9 system.  Man says you may need to install ghostscript-doc and view the pages in /usr/share/doc/ghostscript/

**Looks like “-o” is a shorthand to replace the “-dBATCH -dNOPAUSE” combination.  https://www.ghostscript.com/doc/9.20/Use.htm