Sometimes it might be necessary to start in single-user mode to do some administration work, or even reset an existing password. Normally this can be achieved via the GRUB boot loader. CentOS / RedHat (with root account enabled) Switch on your system. Press Esc until the GRUB menu shows up.…
ZFS ‘Failed to start Mark current ZSYS boot as successful’ fix
On Ubuntu 20.04 after installing the NVIDIA driver 510 metapackage the system stopped booting. It will either hang with a black screen and blinking cursor on the top left or show the following error message: Attempting to revert from a snapshot ends up with the same error message. This wasn’t…
Linux / Unix: Comparing differences between folders
I had to check the file changes between two Backintime snapshots recently. You can always use rsync for that, but there is a more straightforward way by using diff. -q will display only the files that differ. -r will make the comparison recursive. There is a GUI application called Meld…
Raspberry Pi : Configuring a Time Capsule/Backintime server
In this post, I am setting up a Time Capsule and Backintime server. I am using a Raspberry Pi that has Ubuntu installed, with a USB disk that has been configured into a ZFS pool. Setting up backup users You are going to have to create users for each of…
ZFS: Setting up ZFS storage on Ubuntu
If you are new to ZFS, I would advise doing a little bit of research first to understand the fundamentals. Jim Salter’s articles on storage and ZFS are very recommended. https://arstechnica.com/information-technology/2020/05/zfs-101-understanding-zfs-storage-and-performance/ The examples below are to create a pool from a single disk, with separate datasets used for network backups.…
Linux / Ubuntu / hdparm: Identifying drive features and setting sleep patterns
Preparing the storage Install hdparm and smartmontools Install hdparm and the SMART monitoring tools. Identify the right hard drive Make sure you identify the correct drive, as some of the commands will destroy data. If you don’t understand the commands, then check them first. You have been warned. Identify the…
NTP: Setting up an NTP server
Setting up an NTP server chrony is the default service on newer OS releases (Red Hat 7.2 and later, any recent Ubuntu release). chrony has several advantages over ntpd: Quicker synchronisation. Better response to changes in clock frequency (very useful for VMs). Periodic polling of time servers isn’t required. It…
SNFS/Xsan: Quantum SNFS metadata controller and Xsan client compatibility chart
In a previous life, I designed and built many SANs based on Xsan (I believe I started with Xsan 1.3). I then migrated to looking after SANs based on SNFS, either from 3rd party vendors, or Quantum. I believe that the age of Fibre Channel is long over (although SNFS…
macOS : Removing caches and temporary files in macOS
The easiest way is using an application like Onyx. You can check the amount of space taken by the files using du. Before using any deletion command you can check with ls what exactly is going to be deleted. When using rm enable verbose mode (-v). Don’t delete the root…
Raspberry Pi: Installing, hardening and optimising Ubuntu 20.04 Server
I have been trying to document the process of configuring a Raspberry Pi as a Time Machine Capsule, but the article became far too long. It covered far too much information and was really hard to read. I then decided to break the stages into more manageable steps. This has…