drmalex07

README - Restore IPVS table (systemd service)

Lets assume our IPVS table is saved under /usr/local/etc/ipvs-table (e.g. as the output of ipvsadm -S).

Create the service file at /etc/systemd/system/restore-ipvs-table.service:

[Unit]
Description=Restore IPVS table from file
After=network.target

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public class DurationToString
{
    private final Duration duration;
    
    private final TimeUnit unit;

    private DurationToString(Duration d, TimeUnit u)
    {
        this.duration = d;
        this.unit = u;

drmalex07

README

At server

In this example we launch an H2 server, but it doesnt matter; same for any Java process.

Create a password file at ~/.jmxremote.password using $JRE_HOME/lib/management/jmxremote.password as a template.

JMX_PORT=1616

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README - Get Java heap usage

First, find PID of the Java process (e.g by using jps -lvm).

Use jstat to get measurements on the usage/capacity of the several memory pools of the heap (see also man jstat). The results are reported in kbytes.

Get heap capacity, usually referred to as commited size (i.e memory allocated from the OS), by summing up S0C, S1C, EC, OC columns:

jstat -gc ${pid} | gawk '{if (NR > 1) {printf("%.0fk\n", ($1 + $2 + $5 + $7))}}'

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--
-- An example of a function returning a (single) record of (integer, integer, text)
--

CREATE OR REPLACE FUNCTION examine_change_of_status(
    IN status text, IN prev_status text,
    -- output parameters (correspond to fields of returned record)
    OUT a_count integer, OUT b_count integer, OUT answer text) 
AS $body$
BEGIN

drmalex07

README - Setup Docker registry

Let's assume that the FQDN name of the server will be registry.localdomain, and the service will be exposed as https://registry.localdomain:8443/.

1. Prerequisites

Create an environment file .env for the docker-compose project. An example content:

COMPOSE_PROJECT_NAME=registry_localdomain

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# Run with: ansible-playbook -b

---

 - hosts: all
 
   pre_tasks:

   - command: lsb_release -is
     register: lsb_release_distributor_result

drmalex07

Readme - Create a Docker volume on NFS

In this example, we directly instruct Docker to maintain a volume backed by NFS storage. Another way, of course, is to mount the NFS folder at the system level (afterwards, any container can bind-mount it).

By adding a Docker volume backed by NFS, Docker engine will take care of mounting/unmounting based on how containers are using this volume.

See also this comment:

drmalex07

README - Create bootable USB with GRUB2

Let /dev/sdb be the USB device. Create 1 VFAT partition at /dev/sdb1 and mount at /mnt/usb0.

Install GRUB on the device:

grub-install --boot-directory=/mnt/usb0/boot /dev/sdb

Now, all files needed by GRUB (e.g modules for filesystems) are under /mnt/usb0/boot/grub.

drmalex07

package com.example.hello_spreadsheet;

import java.io.Serializable;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.TimeZone;