Well, I learned something new. Responses in email do not show up here.
My email pointed out that I did not snip the fdisk -l command. That snip was made by aggie in response to me. I’m a slow learner, but I learned to follow commands. Also new to me was what aggie pointed out about the 4 entry limit in the DOS partition.
A legacy (DOS) partition table in a modern Linux libata (scsi) context can only hold up to 63 or 64 accessible entries: 3 primaries, plus 60 or 61 logicals (2^6=64). For several years, total logicals were subject to a 2^4=16 limit, before libata was enhanced. This was recent enough that some current Linux users still may be subjected to this lower limit. Other operating systems have both higher or lower limits.
A legacy partition table is the last 66 bytes of each of a non-contiguous chain of sectors. The first sector in the table sector chain, what people typically term “the” partition table, is at the end of the first sector on the disk, called the MBR. Those 66 bytes have space for four 16 byte partition definition entries. Each of the four is termed a primary partition. One of the primaries, when one or more logicals exist, is also termed an extended partition. An extended partition table entry doesn’t define any partition directly. It’s just a sequence of bytes in the initial table chain sector which contains a pointer to the next sector in the table sector chain, where the the logical is defined, along with a pointer to the next table chain sector, if one exists. Here you may see this explained better.
You are correct. I did not pay enough attention to what came from you. I apologize.
While all the details of the exact number of bytes, etc. is true I have no doubt, the answer of @aggie about DOS partitioning was good enough to explain about the max of four (4) partitions and the use of the extended partition. IMHO, in this context the using of “as many as wanted” helps the OP to understand what is going on. After all, does anybody want more then 60 partitions?
I have a disk with 64. 15.4 is booting on 63:
# lsblk -f
NAME FSTYPE FSVER LABEL UUID FSAVAIL FSUSE% MOUNTPOINT
sda
...
├─sda63 ext4 1.0 asu8s154 59a14644-6f5e-4947-91ca-4648a60ee185 996.9M 81% /disks/s154
└─sda64
Time will tell when 64 is put to use whether it will boot, or even be accessible.
Excessive situation for those in the know. But not something to bother the average home user with.
And of course, anybody who, for whatever reason, feels need to follow you, will not use MS-DOS partitioning anymore.