helenchw/misc.md

## misc.md

      
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              misc.md
            
          
    This is a set of notes on miscellaneous computing-related items, ranging from hardware setup to software tools.
They are mainly for my own reference and hopefully it will also be useful to others in need.

  
## misc_hardware.md

      
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              misc_hardware.md
            
          
    Notes on Hardware Details

SGX v2 on Intel Scalable Processors

8 DIMM slots filled per socket requirements

Dell R660 Server Manual
Lenovo SR630v3 Server Manual


## misc_measurement.md

      
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              misc_measurement.md
            
          
    Disk performance

Read

Command:
sudo hdparm -Tt <device name>
Example output (7.2K RPM 1TB SATA HDD):
/dev/sda:
 Timing cached reads:   28196 MB in  1.98 seconds = 14211.59 MB/sec
 Timing buffered disk reads: 578 MB in  3.00 seconds = 192.50 MB/sec


## misc_nedge_ncloud.md

      
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              misc_nedge_ncloud.md
            
          
    Problems/Issues

Installation on CentOS 7

For CentOS 7 without upgrade to 7.9, the original kernel is too old to support the getrandom() (see the closed issue for boost::uuids here).
To resolve the issue, we need to upgrade the kernel via yum and reboot the machine to load the new kernel.

  
## misc_os.md

      
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              misc_os.md
            
          
    Operating-System-Related

OS Installation

CentOS 7


Where to download archived CentOS ISOs?

Check the CentOS vault (https://vault.centos.org/).
Choose the folder named by version.
Go to the sub-folder Linux/isos.


Updating archived CentOS yum repository targets (for CentOS 7.9.2009)

Open /etc/yum.repos.d/CentOS-Base.repo
Comment all lines starting with 'mirrorlist'
Uncomment all lines starting with '#baseurl'
For each line starting with 'baseurl', change the part of http://mirror.centos.org/centos/$releasever to http://vault.centos.org/7.9.2009/.


Upgrading from 7.x to 7.9

Set the yum repository links to vault link of version 7
Upgrade everything using yum -y update
Reboot to reload the upgraded kernel


Firewalld


Setup a new service for port openning (Digital Ocean reference)

(With root access for the following steps)
Construct a service definition file, e.g., mywebservice.xml under /etc/firewalld/services
Input the following contect and replace the service name, port range, and protocol accordingly
<?xml version="1.0" encoding="utf-8"?>
<service>
  <short>MyWebService</short>
  <port protocol="tcp" port="11010-11020"/>
  <port protocol="tcp" port="443"/>
</service>

Force the firewall daemon to reload (the service configurations): firewall-cmd --reload
Find the zone with the target interface: firewall-cmd --list-all
Add the service to the target zone: firewall-cmd --add-service mywebservice --zone=<targetZone> --permanent
Reload the firewall daemon: firewall-cmd --reload


Network Gateway Setup

Using iptables

(Reference: https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/4/html/security_guide/s1-firewall-ipt-fwd#s1-firewall-ipt-fwd)
Assume

interface for internal network: ens3f0np0
interface for external network: eno12399

sudo iptables -A FORWARD -i ens3f0np0 -j ACCEPT
sudo iptables -A FORWARD -o ens3f0np0 -j ACCEPT
sudo iptables -t nat -A POSTROUTING -o eno12399 -j MASQUERADE 

  
## misc_software.md

      
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              misc_software.md
            
          
    Network-related

Netplan


Netplan not working and complaining about a missing module netifaces (because of python version mismatch): Set the perferred python version
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.7 1


Update the network interface name using Netplan

Identify the mac address ("serial") via sudo lshw -C network
Add the following to the interface to rename
match:
  macaddress: <serial>
set-name: <new-interface-name>


Video processing


Check for video length using ffmpeg tools
ffprobe -i <video_file_path> -show_entries format=duration -v quiet -of csv="p=0"


System Monitoring

Fluentbit (Docker)

For statistics collection using the node metrics input plugin,

Incorrect network interfaces: Expose the Docker container to the host network using --network=host
Disk read/write size in bytes: Check the device sector size using blockdev --getbsz <dev> and multiple the metric node_disk_read_bytes_total/node_disk_write_bytes_total to get the exact disk traffic volumes

The metric value collected by fluentbit is in disk sectors (instead of bytes) according to the Linux kernel documentation (https://docs.kernel.org/block/stat.html)


R chart plot

Plot legend only

The example script from https://www.geeksforgeeks.org/draw-ggplot2-legend-without-plot-in-r/
# Load Packages 
library("ggplot2") 
library("grid") 
library("gridExtra") 
library("cowplot") 
  
# Create a DataFrame 
data <- data.frame( 
  Xdata = rnorm(10), Ydata = rnorm(10), 
  LegendData = c("ld-01", "ld-02", "ld-03", 
                 "ld-04", "ld-05", "ld-06", 
                 "ld-07", "ld-08", "ld-09",  
                 "ld-10")) 
  
# Create a Scatter Plot 
gplot <- ggplot(data, aes(Xdata, Ydata, color = LegendData)) +    
  geom_point(size = 7) 
  
# Draw Only Legend without plot 
# Grab legend from gplot 
legend <- get_legend(gplot)                     
  
# Create new plot window 
grid.newpage()                               
  
# Draw Only legend  
grid.draw(legend) 
Code snipplet by Microsoft Copilot
# Create an empty plot
plot(0, type = "n", xlim = c(0, 1), ylim = c(0, 1), xlab = "", ylab = "")

# Add a legend
legend(x = "topright", legend = c("J0", "J2"), lty = c(1, 2), col = c(2, 3), lwd = 2)
PDF Editing


PDF Rotation: pdftk (Ubuntu manual)

Example: Upside down pdftk <input PDF path> cat 1-endsouth output <output PDF path>


PDF Merging: pdfunite (Ubuntu manual)

Example: pdfunite <input PDF path> ... <output PDF path>


## misc_testbed.md

      
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              misc_testbed.md
            
          
    Notes on Testbed deployment

Install S3 storage CA certificate on Ubuntu


Copy the CA certificate to the Ubuntu certificate directory (official guide)

sudo apt-get install -y ca-certificates
sudo cp local-ca.crt /usr/local/share/ca-certificates
sudo update-ca-certificates
Setup Hostname record for S3 storage SSL certificate

In /etc/hosts, add an entry <target ip> nedge-proxy.
MVN


Set up http and https proxies in the user MVN profile (.m2/settings.xml) (official guide)

<settings>
  <proxies>
   <proxy>
      <id>example-proxy</id>
      <active>true</active>
      <protocol>http</protocol>
      <host>proxy.example.com</host>
      <port>8080</port>
      <username>proxyuser</username>
      <password>somepassword</password>
      <nonProxyHosts>www.google.com|*.example.com</nonProxyHosts>
    </proxy>
  </proxies>
</settings>

  
## misc_virt.md

      
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              misc_virt.md
            
          
    Virtualization related

Libvirt

Libvirt network not working on Feodora 41


Change/Set the following option in /etc/libvirt/network.conf

firewall_backend = “iptables”


Restart the libvirtd service

sudo service libvirtd restart
Reference solution: https://gitlab.com/libvirt/libvirt/-/issues/645
Libvirt Windows Guest Display Resolution Locked

To 'unlock' (i.e., enable resolution adjustment), install the guest tools (drivers) for virtio.

Install the virtio guest tools for Windows (choose stable-virtio): https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/

Reference: https://forum.linuxconfig.org/t/libvirt-vm-screen-size-unable-to-select-resolution-with-ms-windows/8169/2