I would like to automate some services using cron jobs.  When I try to edit the crontab file at /etc/crontab, I am not able to save it as it says that it is read only.   What can I do?
I can't seem to edit and save config files in the root system (eg: /etc/dhcp/dhcpd.config); it just says "permission denied" or the save option is blocked in the text editor.  I'm pretty sure I'm a root user, but how do I make sure? If I am a root user, how do I fix this?
koma-script/scrlayer-scrpage: How to get rid of the rulers at the page edge when enabling the draft class option? Is it possible to get rid of these rulers when enabling draft class option?  \RequirePackage{luatex85} \documentclass[draft]{scrreprt}  \usepackage{scrlayer-scrpage}  \usepackage[tuenc]{fontspec} \usepackage{graphicx,mwe}  \begin{document}  \begin{figure}[h]     \centering     \includegraphics[width=\textwidth]{example-image} \end{figure}  \end{document} Why can't I find the Karin Kuruma? When should I upgrade my camera body? What is the best way to get the names of all of the tables in a specific database on SQL Server? For some reason, be it some bad habit or something else, I can not understand why the statement "p only if q" would translate into p implies q. For instance, I have the statement "Samir will attend the party only if Kanti will be there." The way I interpret this is, "It is true that Samir will attend the party only if it is true that Kanti will be at the party;" which, in my mind, becomes "If Kanti will be at the party, then Samir will be there."   Can someone convince me of the right way?  EDIT:  I have read them carefully, and probably have done so for over a year. I understand what sufficient conditions and necessary conditions are. I understand the conditional relationship in almost all of its forms, except the form "q only if p." What I do not understand is, why is p the necessary condition and q the sufficient condition. I am not asking, what are the sufficient and necessary conditions, rather, I am asking why. Limit- almost finished, however hint needed. Maximum weight an average bicycle can carry? A few years ago, I've bought  (see edit) bike. At that time I was around 90 kgs and I didn't have any problems.  Today I'm around 120 kgs and I was considering (among other things) starting cycling again. Is this bike "good" enough to carry me? What should I expect? Any tips?  EDIT! Apparently, Drag have renamed some of their bikes in the last few years, so the above information is a bit wrong.  seems to be my bike. At first I didn't recognize much difference, but this one has suspension on the front which mine also has. Does this change anything Execute a large SQL script (with GO commands) Joda Time: How to get dates of weekdays on some date interval? How do I lock compiled Java classes to prevent decompilation?  I know this must be very well discussed topic on the Internet, but I could not come to any conclusion after referring them.  Many people do suggest obfuscator, but they just do renaming of classes, methods, and fields with tough-to-remember character sequences but what about sensitive constant values?  For example, you have developed the encryption and decryption component based on a password based encryption technique. Now in this case, any average Java person can use  to decompile the class file and easily retrieve the password value (defined as constant) as well as  and in turn can decrypt the data by writing small independent program!  Or should such sensitive components be built in native code (for example, VC++) and call them via ? Cannot remove any bluetooth device How to validate an email address in PHP I'm trying to change the numbers in problems I write for examples I use in my class as well as assignments. However the problems are still inspired by the textbook. Are the problems sufficiently different from the textbook problems to not have copyright issues? There is also an issue of theorems and definitions. Authors of the calculus textbook certainly did not come up with these things. Is it OK to just copy them down in my lecture notes?  By the way I do share my lecture notes on Piazza and the course I'm teaching is multivariable calculus. Area of a quadrilateral proof Get next / previous element using JavaScript? For some reason I can't boot my system. I get an error akin to Operating System Not Found.   I tried bootrepair, and that didn't work. So then I decided I would just save my personal files, wipe everything, and reinstall.   But in the live session, when I go to the /home directory, my username folder isn't there, instead it goes to the Live CD's desktop and other directories. Is there some other error occurring? Is there a way to recover the files? Why does my user number show up in the search box when clicking my profile information? Hey all-  I just noticed that if you click on your username on the top bar, when your profile shows up, in the search bar at the top you'll find an explicit search for your user account.  For my meta account, for example, I see user:157031 whenever I click on my profile.  Is this deliberate?  If so, can I suggest removing that text?  It means that I have to manually delete the contents of the search field if I want to do a search from my profile screen.  Thanks! Evaluate trigonometric function Why didn't Thanos come to Earth to retrieve Tesseract by himself? In the Avengers movie, why didn't Thanos personally come to Earth instead of Loki? Or, if Loki's skills were required, why didn't he come with Chitauri? He knew that humans were primitive; there wouldn't be any threat and he could personally secure Tesseract.  AFAIK, the movie didn't display much. Is there any other source answering this? How was this answer posted after this question was closed?