Category: Ubuntu

mdadm is used to manage software RAID. Install mdadm package with

apt install mdadm

To set up RAID 1 (mirror), you need 2 drives or partitions of the same size

Setup Partition

Create a partition with the following commands on both the drives used for RAID 1.

parted /dev/sdX mklabel gpt
parted /dev/sdX mkpart primary ext4 0% 100%
parted /dev/sdX set 1 raid on
parted /dev/sdX print

Replace /dev/sdX with device name of the drive you will be using for the RAID.

Create RAID 1

To create a RAID 1 mirror, use the following command

IMPORTANT: Do not cut and paste without understanding what you are doing, you need to replace device names to avoid data loss.

mdadm --create --verbose /dev/md0 --level=1 --raid-devices=2 /dev/sdb1 /dev/sdc1

In the above command, replace /dev/md0 with the device name of the RAID array you need. If your system already has a raid array with this name, use another name, for example: /dev/md1.

/dev/sdb1 and /dev/sdc1 = replace these with the device name of the drives you will be using for the RAID 1

To see the raid status, use the command

cat /proc/mdstat

To find details, use the command:

mdadm --detail /dev/md0

Formatting the RAID drive

Once you created a RAID array, you need to format it with the command

mkfs.ext4 /dev/mdX

/dev/mdX = replace it with the actual device name used while creating the RAID array.

mkfs.ext4 will format the drive with EXT4 file system. To use other supported file systems replace mkfs.ext4 with other available file system types. For example mkfs.xfs

Mount the Drive

To mount the drive, use the following commands

mkdir /backup
mount /dev/md0 /backup

This will mount /dev/md0 as /backup. Change the mount point and device name as needed.

Auto Assemble RAID on the boot

To ensure the array is reassembled automatically at boot, update the mdadm configuration file:

mdadm --detail --scan

Add entry for the RAID array in file /etc/mdadm/mdadm.conf

Update the initramfs:

update-initramfs -u

Make the Drive auto-mount

To automount the drive on boot, edit /etc/fstab

vi /etc/fstab

Add the following line

/dev/md0 /backup ext4 defaults 0 2

Verify it is mounting properly with the command

mount -a

Back to RAID

Keeping your operating system up-to-date is crucial for maintaining security and stability. For Ubuntu/Debian users, the unattended-upgrades package offers a solution to automate this essential task

Unattended-upgrades is a package for Ubuntu and other Debian-based Linux distributions that automates the process of keeping your system up-to-date. Its primary purpose is to automatically install security updates without requiring manual intervention from the system administrator.

To install unattended-upgrades, run

sudo apt install unattended-upgrades

To configure, edit file

sudo vi /etc/apt/apt.conf.d/50unattended-upgrades

Uncomment the line

//      "${distro_id}:${distro_codename}-updates";

To make it look like

Unattended-Upgrade::Allowed-Origins {
        "${distro_id}:${distro_codename}";
        "${distro_id}:${distro_codename}-security";
        // Extended Security Maintenance; doesn't necessarily exist for
        // every release and this system may not have it installed, but if
        // available, the policy for updates is such that unattended-upgrades
        // should also install from here by default.
        "${distro_id}ESMApps:${distro_codename}-apps-security";
        "${distro_id}ESM:${distro_codename}-infra-security";
        "${distro_id}:${distro_codename}-updates";
//      "${distro_id}:${distro_codename}-proposed";
//      "${distro_id}:${distro_codename}-backports";
};

Uncomment the following line, this helps if you need a quick reboot while an upgrade is running, good for desktops/workstations.

//Unattended-Upgrade::MinimalSteps "true";

Another configuration file is /etc/apt/apt.conf.d/20auto-upgrades, default values are fine for this.

sudo vi /etc/apt/apt.conf.d/20auto-upgrades

To debug unattended upgrade, run

sudo unattended-upgrade --dry-run --debug

Back to Ubuntu

DHCP, or Dynamic Host Configuration Protocol, is a network management protocol that automates the process of assigning IP addresses and other network configuration parameters to devices on a network. This crucial technology plays a vital role in modern network infrastructure, from small home networks to large enterprise environments.

In essence, DHCP eliminates the need for manual IP address configuration, making it easier for devices to join and communicate on a network. It dynamically assigns IP addresses, subnet masks, default gateways, and other network settings to client devices, streamlining network administration and reducing the potential for configuration errors.

dhclient

On Ubuntu systems, dhclient works in conjunction with NetworkManager for easier network configuration management.

Configuration file located at /etc/dhcp/dhclient.conf

To view IP lease info, run “dhclient -v” command

root@sok-mysql-fix:~# dhclient -v
Internet Systems Consortium DHCP Client 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/

Listening on LPF/eth0/00:16:3e:bf:97:d0
Sending on   LPF/eth0/00:16:3e:bf:97:d0
Sending on   Socket/fallback
DHCPDISCOVER on eth0 to 255.255.255.255 port 67 interval 3 (xid=0xc266324)
DHCPOFFER of 10.18.211.81 from 10.18.211.1
DHCPREQUEST for 10.18.211.81 on eth0 to 255.255.255.255 port 67 (xid=0x2463260c)
DHCPACK of 10.18.211.81 from 10.18.211.1 (xid=0xc266324)
RTNETLINK answers: File exists
bound to 10.18.211.81 -- renewal in 1759 seconds.
root@sok-mysql-fix:~# 

Or check the content of file /var/lib/dhcp/dhclient.leases

root@sok-mysql-fix:~# cat /var/lib/dhcp/dhclient.leases
lease {
  interface "eth0";
  fixed-address 10.18.211.81;
  option subnet-mask 255.255.255.0;
  option routers 10.18.211.1;
  option dhcp-lease-time 3600;
  option dhcp-message-type 5;
  option domain-name-servers 10.18.211.1;
  option dhcp-server-identifier 10.18.211.1;
  option dhcp-renewal-time 1800;
  option broadcast-address 10.18.211.255;
  option dhcp-rebinding-time 3150;
  option host-name "sok-mysql-fix";
  option domain-name "lxd";
  renew 0 2024/07/07 17:47:55;
  rebind 0 2024/07/07 18:11:06;
  expire 0 2024/07/07 18:18:36;
}
root@sok-mysql-fix:~# 

To manually request a lease

 dhclient <interface>

To release an IP address

 dhclient -r <interface>