Some helpful commands for showing hardware information on Linux.
Show memory speed
sudo dmidecode --type 17
Show CPU Frequency in MHz
cat /proc/cpuinfo | grep MHz
Show a bunch of system info with inxi, may need to install it.
inxi
Another cool program is screenfetch. Gives a nice overview of system specs
sudo dnf install screenfetch
and run with
screenfetch
Not sure why it was giving an error. But to resolve the issue
click on “Software Sources”
On the Network line put http://mirror.centos.org/centos-8/8/BaseOS/x86_64/os/
Should be able to go back to the previous page and select what you want to install.
Enabling logging on firewall rules can be beneficial for tracking why a certain rule is not behaving as you intended.
Enabling logging is relatively straight forward.
Quickest way to enable logging is to run
sudo firewall-cmd --set-log-denied=all
This changes the options in the /etc/firewalld/firewalld.conf config file. Options include all, unicast, broadcast, multicast, and off
The command also reloads the firewall so manually restarting the firewall is necessary.
You can use dmesg to view the failed attempts or you can follow the messages log and filter to just show the rejects
sudo tail -f /var/log/messages | grep -i REJECT
You can now try to access the server or run a test to trigger a log event. In my case I tried initiating a SSH connection.
Oct 1 16:32:10 localhost kernel: FINAL_REJECT: IN=eno1 OUT= MAC=f8:ab:98:12:fe:11:a1:ec:a6:00:67:3e:97:00 SRC=192.168.1.1 DST=192.168.88.2 LEN=60 TOS=0x08 PREC=0x40 TTL=59 ID=43080 DF PROTO=TCP SPT=38192 DPT=22 WINDOW=52240 RES=0x00 SYN URGP=0
Interesting bits are bolded. Our destination port it 22 “ssh” and our source address is 192.168.1.1. If I want this IP to access the server, I’ll need to add the 192.168.1.1 IP range in the allowed IP ranges.
After you have finished troubleshooting your problem, you may want to turn the logging feature off so you don’t fill up the logs with failed entries.
You can turn it off with
sudo firewall-cmd --set-log-denied=off
We can verify that logging is off by running
sudo firewall-cmd --get-log-denied
If the firewall logging option is off it will return “off”
The following site has some more information and alternative ways
https://www.cyberciti.biz/faq/enable-firewalld-logging-for-denied-packets-on-linux/
You sometimes need to set the coolbits value to overclock your GPU on Linux
You’ll need to install nvidia-xconfig
sudo dnf install nvidia-xconfig
Then you can set the cool bits value with the following command. Change 24 to the appropriate cool bits value. Refer to the link below.
sudo nvidia-xconfig --cool-bits=28
It’ll create a new xorg config file. Reboot to take advantage of cool bits being enabled.
Multiple GPUs
If you have multiple GPUs, you will need to do the following to enable cool bits on each GPU.
sudo nvidia-xconfig -a --cool-bits=28 --allow-empty-initial-configuration
https://wiki.archlinux.org/title/NVIDIA/Tips_and_tricks#Enabling_overclocking
Recently I started getting the following error while running ./validate.php.
$ sudo -u librenms ./validate.php
====================================
Component | Version
--------- | -------
LibreNMS | 21.8.0-41-g0a76ca4
DB Schema | 2021_08_26_093522_config_value_to_medium_text (217)
PHP | 7.4.20
Python | 3.6.8
MySQL | 10.5.10-MariaDB
RRDTool | 1.4.8
SNMP | NET-SNMP 5.7.2
====================================
[OK] Composer Version: 2.1.6
[OK] Dependencies up-to-date.
[OK] Database connection successful
[FAIL] Database: incorrect column (notifications/datetime)
[FAIL] Database: incorrect column (users/created_at)
[FAIL] We have detected that your database schema may be wrong, please report the following to us on Discord (https://t.libren.ms/discord) or the community site (https://t.libren.ms/5gscd):
[FIX]:
Run the following SQL statements to fix.
SQL Statements:
SET TIME_ZONE='+00:00';
ALTER TABLE `notifications` CHANGE `datetime` `datetime` timestamp NOT NULL DEFAULT '1970-01-02 00:00:00' ;
ALTER TABLE `users` CHANGE `created_at` `created_at` timestamp NOT NULL DEFAULT '1970-01-02 00:00:01' ;Reading online it sounds like some of the recent changes are causing the issue. Looks fairly easy to resolve though.
First we’ll need to get a MySQL prompt. We’ll do that by running
mysql -u librenms -p librenms
It’ll ask use for the librenms user’s mysql password.
Once we have the MySQL prompt we can just copy and paste the commands in.
SET TIME_ZONE='+00:00'; ALTER TABLE `notifications` CHANGE `datetime` `datetime` timestamp NOT NULL DEFAULT '1970-01-02 00:00:00' ; ALTER TABLE `users` CHANGE `created_at` `created_at` timestamp NOT NULL DEFAULT '1970-01-02 00:00:01' ;
Type ‘quit’ to exit MySQL and lets run the validate script again.
sudo -u librenms ./validate.php
Everything should check out OK.
Installing Linux GUI applications seems fairly easy on WSL 2. Main requirement is to have the graphics driver installed and the WSL being on version 2.
https://docs.microsoft.com/en-us/windows/wsl/tutorials/gui-apps
You can list WSL versions by running
wsl --list --verbose
This is a very simple ping script I created to run on a remote UniFi device to scan for other IP addresses on it’s network. It works on SH environments as well as Bash.
Paste the script in a ping.sh file and then
chmod +x ping.sh
run like so, replacing 192.168.1. with the IP range you want to scan.
sh ping.sh 192.168.1.
#!/bin/sh
# simple ping scan utility
# i.e. 192.168.0.
ipFirstPart=$1
ip=0
while [ $ip -ne 255 ]
do
ip=$(($ip+1))
ping -w1 $ipFirstPart${ip} | grep "64 bytes from"
done
There may be a different and easier way to do this, but the main thing to learn here is the ^, $, and [[:digit:]] options.
^ refers to the first part of a line
& which is our searched for pattern
$ refers to an end part of the line
[[:digit:]] searches for, you guessed it. Digits!
The following command reads the incoming 10 digit number form echo and does the following.
the ^ tells it that the pattern needs to match at the beginning of the line
[[:digit:]] repeated tells it to search for three consecutive digits
(&) tells it to put brackets around the & which is our searched for pattern in the first part.
We then pipe that to another sed command which
searches for 4 consecutive digits
the $ tells it that it needs to be at the end of the line.
echo "1234567890" | sed -e 's/^[[:digit:]][[:digit:]][[:digit:]]/(&) /g' | sed -e 's/[[:digit:]][[:digit:]][[:digit:]][[:digit:]]$/-&/g'
Resulting output is
(123) 456-7890
The following link was helpful while searching what the ^ and $ options do.
This is fairly straight forward to resolve. You can run the following command and replace /media/username/drive with the path to your drive.
sudo chmod ugo+wx /media/username/driveIf you need to locate the path to your drive, try running
lsblk
It should show all the hard drives mount points
https://askubuntu.com/questions/90339/how-do-i-set-read-write-permissions-my-hard-drives
List snapper BTRFS snapshots with
snapper list
If you are in recovery mode on Fedora, add –no-dbus right after the snapper command. e.g.
snapper --no-dbus list
You can use the diff command to list the changes that happened between snapshots.
snapper --no-dbus diff 108..109
And to undo a change or all the changes between a snapshot, do the following. Where 108..109 are all the changes you want to remove. So essentially going back to snapshot 108.
snapper --no-dbus -v undochange 108..109
https://documentation.suse.com/sles/11-SP4/html/SLES-all/cha-snapper.html