John's Linux blog

 Where $i is the original name and $nn is the new name: Animated gif to mp4: ffmpeg -i $i -movflags faststart -pix_fmt yuv420p -vf "scale=trunc(iw/2)*2:trunc(ih/2)*2" $nn.mp4 WAV to mp3: In case you have to deal with windows 3.11 users. Just kidding, any windows users. ffmpeg -i $i -vn -ar 44100 -ac 2 -b:a 192k $nn.mp3 Any video to mp4: This is useful if you get MOV files from your phone as they are 3x bigger than mp4: ffmpeg -i $i $-vn -acodec libmp3lame -ac 2 -ab 160k -ar 48000 $nn.mp4 PNG to jpg: This is useful if you get lots of screenshots on your phone as the screenshots are 10x bigger than jpg:      convert $i $nn.jpg

  Introduction The following steps are needed to boot Mac OS under VirtualBox. I tested it using Mac OS X 10.13. I can't guarantee this works. You'll need a source/original mac to copy the OS install. Probably Apple won't approve of this because they want you to buy their original hardware, but sometimes you need hosted VMs in the cloud or similar, and they don't really offer that. Steps Commands below are typed in a command line like the Terminal. 1. On a Mac, do this to download an installer disk: softwareupdate --fetch-full-installer --full-installer-version  ... OR download from the app store. If the operating system you want to install is out of date, ie if the Mac tells you the installer is damaged, set your Mac date and time to however many years ago that operating system came out, and turn of automatic date and time in the date and time system preferences. That way the signature of the installer disk / bundle will still be valid (it is invalid if it is older tha

If windows updated and wiped your linux bootloader, follow these steps.  https://techblog.dev/posts/2021/12/how-to-fix-missing-grub-boot-menu-after-a-windows-update/  

1. Install: bash$  sudo snap install icloud-for-linux 2. Run one of the apps:   bash$ icloud-for-linux.keynote 3. Drag to your Dock (launcher panel) easy

LVM is the Logical Volume Mapper, which lets you tell Linux that a volume (drive or partition) is part of a group of volumes/drives/partitions, which are considered one drive and which act together as one, called a "volume group".  If you run out of space on a Linux machine and you are using LVM, you can enlarge the drive and make it act as if it were a single drive, by adding another drive and then telling it to add that drive to the LVM volume group. You can tell that your drive is LVM if you see mention of LVM in the output of the "disk free" command, df. Note the wording "dev/mapper" Filesystem                         Size   Used Avail Use% Mounted on udev                               399M     0   399M   0% /dev tmpfs                               85M   956K   84M   2% /run /dev/mapper/ubuntu--vg-ubuntu--lv   194G   93G   93G   51% / Here's the simplest way to do it. Assume you have an existing drive called /dev/sda1, and it is almost full. Assume

 If /var/log/journal is taking up too much space, you can clear it and prevent it growing too big again. Prevention: vi /etc/systemd/journald.conf   Look for: SystemMaxUse=2000M Or similar, and set it to a lower value Then: service systemd-journald restart Clearing once-off: journalctl --vacuum-time=2d assuming for example you want to clear everything before two days ago.