Recently, I used EasyOS to do two things:
* Convert three large PDFs to DjVus to save space on a microSD card.
* Move all my folders and their files from a microSD card having a capaclty of 128GB to one with a capacity of 256GB.
The DjVu format was devised by Bell Labs to store electronic documents similar to the PDF format but with an emphasis on storing scanned documents and images, sometimes more efficiently and compactly than the PDF format. Before Adobe released the source code for the basic PDF functionality, the Internet Archive (archive.org/texts), also prepared documents in DjVu format. Documents are stored in that format with an image layer separation of text and images. On the one hand, this results in higher compression of documents with coloured images, while, on the other hand, all the fonts used in a document are stored there. This is unlike the PDF format, where fonts expected to be available in a computer system are not stored with the document.
As the microSD card I was using on my Android tablet was running out of capacity, I knew I had to take steps to reduce the size of some of my documents. The file manager on the tablet allowed me to display all my files regardless of the directories they were stored in and then sort them by size (from the largest down). In my case, the Cours d'Analyse by Jordan in PDF format was 1.33GB and similarly, there was a document on shade plants with 340MB in PDF format and an illustrated history with a size of 320MB, again in PDF format. I uploaded these documents to the cloud and downloaded them into EasyOS Daedalus. I had previously installed the program pdf2djvu and its dependencies. I invoked the program on each of these documents individually in a terminal and got the conversion progress on a page by page basis. Years ago, I had used Puppy Linux for the same purpose. Today, the converted documents in DjVu format are, successively, 1.21GB, 3MB and 105MB.
Regarding the second task, I finally realized that it was time to replace my 128GB microSD card with a higher capacity one. I chose a 256GB card of the same brand. My challenge was to copy all the directories with the attendant files from the 128GB card to a 256GB card. I decided not to rely on the SD slot on my Linux laptop as it was limited to 64GB in any case. I placed the 128GB card in an SD card reader, which now was treated by Linux as a USB device. I thought it prudent to first back up the card's contents to a Seagate 500GB portable external drive. Knowing that copying was a delicate task, rather than do a direct copy of the entire card. which is doomed to failure, I entered on the drive the various directories and only did a copy of a directory that contained files. I then used the tree command on the source and destination to compare the number of sub-directories and files in each of the directories that I had copied. If there was a discrepancy, I then checked all of the sub-directories to locate the error. After doing a tree command on the master directories for the source and destination as a final check, I then ejected the 128GB card and inserted the 256GB card, doing the same procedure only in reverse.