Keep a specific package version pinned on Rocky Linux with dnf versionlock.
Install the plugin if you haven't:
sudo dnf install python3-dnf-plugin-versionlock
Then:
sudo dnf versionlock add <package> -- lock it
sudo dnf versionlock list -- see what's pinned
sudo dnf versionlock delete <package> -- release the lock
Handy for holding a kernel, database, or app version steady while everything else updates.
#RockyLinux #Linux #TechTipThursday #SysAdmin
Your Linux host is only as secure as you make it.
Check who's logged in right now: who
See open network connections: ss -tulnp
Check for listening services you don't recognize:
systemctl list-units --type=service --state=running
If you can't explain why a service is running, that's your homework.
#Linux #SysAdmin #Security #TechTip
Here's a few dnf commands that are easy to overlook but genuinely useful on Rocky Linux:
dnf history -- full log of installs and removals with timestamps
dnf autoremove -- removes packages nothing depends on anymore
dnf provides <file> -- find out which package owns a specific file
dnf repoquery --installed -- everything currently on your system
What's your go-to dnf command? Share it in the replies.
#RockyLinux #Linux #TechTipThursday #SysAdmin #OpenSource
When the network is broken and you need answers fast:
Trace the route to a host:
traceroute google.com
Check what's listening on your ports:
ss -tuln
Test DNS resolution:
dig google.com
The network is never actually down. Something specific broke. These tell you what.
#Linux #SysAdmin #Networking #TechTipThursday
Networking on Linux isn't magic. It just looks that way until you know where to look!
Check your network interfaces: ip addr show
Test connectivity: ping -c 4 google.com
Check your routing table: ip route show
#TechTipThursday
Printers. The final boss of Linux administration. Check your print service is running:
systemctl status cups
List available printers:
lpstat -p
Send a file to the printer and pray:
lp filename.pdf
Linux has conquered the cloud, the kernel, and the enterprise. Printers remain undefeated.
#TechTipThursday
Yes, Linux admins still configure email. No, it never gets less weird.
Check if your mail service is running:
systemctl status postfix
Send a test email from the command line:
echo "Test" | mail -s "Hello" [email protected]
Check the mail queue:
mailq
Nobody gets excited about email configuration. Until something breaks and logs stop delivering. Then it's the only thing that matters.
Check your system logs:
journalctl -xe
Follow logs in real time:
journalctl -f
Filter by service:
journalctl -u nginx
Logs tell you everything, if you know where to look.
#SysAdmin #Linux #TechTipThursday
Check your system time and timezone:
timedatectl status
Set your timezone:
timedatectl set-timezone America/Chicago
Sync with NTP:
timedatectl set-ntp true
Getting time right matters more than people think, especially for logs, cron jobs, and anything distributed.
#TechTipThursday
Want to check or change your system locale on Linux?
localectl status
To list available locales:
localectl list-locales
To set one:
localectl set-locale LANG=en_US.UTF-8
Handy when you're deploying systems for users in different regions or when something's outputting dates and currencies in a format that makes no sense to you.
#linux #sysadmin
Rocky Linux 
Eric The IT Guy