On Fedora based system, whenever I need help writing a cron task and confused which field is minute, hour, day,..etc, I usually check the /etc/crontab file. ❯ cat /etc/crontab SHELL=/bin/bash PATH=/sbin:/bin:/usr/sbin:/usr/bin MAILTO=root # For details see man 4 crontabs # Example of job definition: # .---------------- minute (0 - 59) # | .------------- hour (0 - 23) # | | .---------- day of month (1 - 31) # | | | .------- month (1 - 12) OR jan,feb,mar,apr ... # | | | | .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat # | | | | | # * * * * * user-name command to be executed Recently, I found an online cron scheduler editor - crontab.guru. It can be used to create a new task expression, or we can use it to verify the existing cron schedule expressions that we have. ...

Another month, another Red Hat exam has been ticked off the list. This time, it’s about the Red Hat Virtualization, a technology based on oVirt. The code name of the exam is EX318, and as rumours has it, it’s one of the easiest Red Hat exams; I can’t agree more. The exam’s duration is 3 hours; it’s a hand-on closed book exams. The exam is based on Red Hat Virtualization version 4.3. ...

I like to keep the firmware running on all my devices up to date. New firmware is released to do to main things: fixing bugs and feature enhancing. Today, I just found out that the modem/router provided by my ISP is running and out of date firmware. The installed firmware is NF18ACV.NC.AU-R6B016.EN released on 2018/05/14. There have been a few new versions of firmware released between then and now, with the latest version being: NC2-R6B021 released on 2020/11/26. ...

I have a FreeIPA server with the following information: FreeIPA server: utility.lab.example.com FreeIPA realm: LAB.EXAMPLE.COM FreeIPA domain: lab.example.com I want to add 2 normal users: User Login: rhvadmin, First Name: RHV, Last Name: Admin, Password: CentOS123^ User Login: normaluser, First Name: Normal, Last Name: User, Password: CentOS123^ [root@utility ~]# ipa user-add rhvadmin --first RHV --last Admin --password Password: CentOS123^ Enter Password again to verify: CentOS123^ --------------------- Added user "rhvadmin" --------------------- User login: rhvadmin First name: RHV Last name: Admin Full name: RHV Admin Display name: RHV Admin Initials: RA Home directory: /home/rhvadmin GECOS: RHV Admin Login shell: /bin/sh Principal name: rhvadmin@LAB.EXAMPLE.COM Principal alias: rhvadmin@LAB.EXAMPLE.COM User password expiration: 20201204121711Z Email address: rhvadmin@lab.example.com UID: 1829600001 GID: 1829600001 Password: True Member of groups: ipausers Kerberos keys available: True [root@utility ~]# ipa user-add normaluser \ > --first Normal --last User --password Password: CentOS123^ Enter Password again to verify: CentOS123^ ... The rhvadmin will be asked to change the password on its first login. To prevent this from happening, we can change the user’s password with kpasswd util. ...

Again, just a quick note to remind myself how to attach a disk to a VM guest from the command line. The following steps is based on these assumptions: A spare disk: an LVM volume name db2_data on data volume group The name/domain of the VM is db2 List the name of the VM guest and available logical volume. [root@mathvm5 ~]# virsh list | grep db2 20 db2 running [root@mathvm5 ~]# lvs | grep db2 db2 vm -wi-ao---- 80.00g db2_data vm -wi-a----- 128.00g Run virsh attach-disk command to attach a disk to a VM. Notice that –persistent option is passed to the command so that this new disk will be permanently attached to the VM. ...