CIDR Subnet Mask Cheatsheet

Netmask              Netmask (binary)                 CIDR     Notes
____________________________________________________________________  11111111.11111111.11111111.11111111  /32  Host (single addr)  11111111.11111111.11111111.11111110  /31  Unuseable  11111111.11111111.11111111.11111100  /30    2  useable  11111111.11111111.11111111.11111000  /29    6  useable  11111111.11111111.11111111.11110000  /28   14  useable  11111111.11111111.11111111.11100000  /27   30  useable  11111111.11111111.11111111.11000000  /26   62  useable  11111111.11111111.11111111.10000000  /25  126  useable    11111111.11111111.11111111.00000000  /24 "Class C" 254 useable
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How to reset root password on Linux server

First we need to boot into recovery mode. To do so, restart server and hold Shift down to call up the boot menu. Then select (recovery mode) for the image you are using. Once you get Recovery menu, select root and press Enter. You will be redirected to recovery console.


At this point we need to mount file system, since it is in RO (read-only) mode. To do so, type the following:
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