How to fix Crontab -e - You are not allowed to use this program (crontab)

Question: I've received a new server and logon, trying to use Crontab but getting this error message: You (your_logon) are not allowed to use this program (crontab) See crontab(1) for more information How can I fix? Answer: It looks like you are experiencing a situation where only root can use crontab - but other logon accounts require some extra steps. On Linux there are two files which control the access to crontab: /etc/cron.allow /etc/cron.deny You will need to add the logon account to the /etc/cron.allow file. The way to add the logon account is to --su to root and then... Read more →

Transparent Huge Pages - Detected startup warnings on a database backing the system

Question: I'm getting these messages as system alerts through the MongoDB Ops Manager. 2020-02-07T21:34:21.241+0000 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'. 2020-02-07T21:34:21.241+0000 I CONTROL [initandlisten] ** We suggest setting it to 'never' What do they mean? and how can I stop these warning messages occuring? Answer: The Transparent Hugepages Linux kernel feature aims to boost performance by by "optimising" the processor's memory mapping. By using larger memory page sizes , the aim is to decrease the Translation Lookaside Buffer(TLB) lookups . By default this feature is enabled in most Linux distributions. MongoDB recommends to Disable Transparent Huge Pages Follow... Read more →

bash: /home/myuser/.ssh/authorized_keys: No such file or directory

Question: When I type in cat ~/.ssh/authorized_keys to a RHEL 7 server I get the following message: cat: /root/.ssh/authorized_keys: No such file or directory I'm going through the process of setting up a SSH to create a connection between BART and client Potgresql servers - to backup Postgresql databases. How can I fix this issue? Answer:You need to create the ssh directory for the first time and create the authorized keys file. Create the .ssh directory. First check if actually already exists mkdir ~/.ssh Set the right permissions for the new .ssh directory. Very important step chmod 700 ~/.ssh Create... Read more →

Top 10 Yoda tips for the Linux command line

Master these Linux commands and you will feel the Force or become the Linux Yoda . (or even just your job done more efficiently) I don't know anything about myprogram - how can I find out? 10 "info myprogram" or 9 "man myprogram" How can I find myprogram ? 8 "locate -i foo" or 7 "whereis foo" How can I view myprogram ? 6 "less foo" or 5 "emacs foo" How can I view the program's help ? This applies to most programs 4 myprogram "-h" or "--help" . How can I navigate further into a directory? 3 "cd ./mydirectory"... Read more →

How to get the Java Toolbox jt400 version through Command Line

Question: How can I get the Jave Toolbox jt400 driver details through the command Line? Answer: To get the version details of the Java Toolbox jt400 version through the command line run this command - making sure you're pointing to the right jar file java -cp ./jt400.jar utilities.AboutToolbox You should see something similar to the following response IBM Toolbox for Java: Open Source Software, JTOpen 9.8, codebase 5770-SS1 V7R3M0.00 built=20190304 @Z0 Supports JDBC version 4.2 Toolbox driver version 11.8 Read more →

How to use an external smtp server with Linux mail \ mailx

Question: How can I use an external smtp server with Linux mail ? I'm using the heirloom-mailx implementation on RHEL. Answer: Here are some examples of using an external smtp server, using the heirloom package on RHEL. --sending an email to an external smtp server - with an attachment mail -v -r "root@myserver.net" -s "Test Email with attachment" -S smtp="smtp-xxxx.xxxx.xxxx.net" -a/tmp/hi_jack.txt "jack@xxxxxx.com" --sending an email to an external smtp server with multiple recipients mail -v -r "root@mysever.net" -s "Test Email with attachment" -S smtp="smtp-xxxx.xxxx.xxxx.net" -a/tmp/hi_jack.txt "jack@xxxx.com,kevin@xxxx.com" --sending an email to an external smtp with message written to body echo "Hi... Read more →