OpenSSL

1
openssl rand -hex 32

pwgen

1
pwgen 32 1

/dev/urandom

1
hexdump -vn32 -e'4/8 "%08X" 1 "\n"' /dev/urandom

• -v to print all data (by default hexdump replaces repetition by *).
• -n16 to consume 16 bytes of input (32 hex digits = 16 bytes).
• 4/8 "%08X" to iterate four times, consume 8 bytes per iteration and print the corresponding 64 bits value as 16 hex digits, with leading zeros, if needed.
• 1 "\n" to end with a single newline.

src: https://stackoverflow.com/a/34329057

tr

1
tr -dc 'A-F0-9' < /dev/urandom | dd bs=1 count=32 2>/dev/null
2
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