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5 Practical “md5sum” Command Usage Examples in Linux This tutorial explains Linux “md5sum” command, options and its usage with examples. “md5sum” command is used to compute and check MD5 message digest. This post describes “md5sum” command used in Linux along with usage examples and/or output. Usage: md5sum [OPTION]… [FILE]… The MD5 message-digest algorithm is a widely used cryptographic hash function that produces a 128-bit (16-byte) hash value.Two non identical files will never have the same md5sum value.However, it has since been shown that MD5 is not collision resistant;[3] as such, MD5 is not suitable for applications like SSL certificates or digital signatures that rely on this property. Here’s the listing of example usage of “md5sum” command: 1. To calculate md5sum(md5sum file_path): sanfoundry- > md5sum out.txt fa328c3f84352dc7ff5e32bba2ac833c out.txt Note md5sum command is not usable for the direct

root@kali:~# apt-get update Get:1 http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease [30.5 kB] Err:1 http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease   The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org> Reading package lists... Done W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: http://ftp.yzu.edu.tw/Linux/kali kali-rolling InRelease: The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org> W: Failed to fetch http://http.kali.org/kali/dists/kali-rolling/InRelease  The following signatures were invalid: EXPKEYSIG ED444FF07D8D0BF6 Kali Linux Repository <devel@kali.org> W: Some index files failed to download. They have been ignored, or old ones used instead. FIX FIRE UP TERMINAL COPY THIS COMMAND AND PRESS ENTER wget -q -O - archive.kali.org/archive-key.asc | apt