{"id":7726,"date":"2019-01-09T12:04:23","date_gmt":"2019-01-09T12:04:23","guid":{"rendered":"https:\/\/www.appservgrid.com\/paw92\/?p=7726"},"modified":"2019-01-12T09:55:54","modified_gmt":"2019-01-12T09:55:54","slug":"linux-today-using-the-ssh-config-file","status":"publish","type":"post","link":"https:\/\/www.appservgrid.com\/paw92\/index.php\/2019\/01\/09\/linux-today-using-the-ssh-config-file\/","title":{"rendered":"Linux Today – Using the SSH Config File"},"content":{"rendered":"
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If you are regularly connecting to multiple remote systems over SSH on a daily basis, you\u2019ll find that remembering all of the remote IP addresses, different usernames, non standard ports and various command line options is difficult, if not impossible.<\/span><\/div>\n<\/div>\n

One option would be to\u00a0create a bash alias<\/a>\u00a0for each remote server connection. However, there is another, much better and more simpler solution to this problem. OpenSSH allows you to set up per-user configuration file where you can store different SSH options for each remote machine you connect to.<\/p>\n

This guide covers the basics of the SSH client configuration file and explains some of the most common configuration options.<\/p>\n

Prerequisites<\/a><\/h2>\n

We are assuming that you are using a Linux or a macOS system with OpenSSH client installed.<\/p>\n

SSH Config File Location<\/a><\/h2>\n

OpenSSH client-side configuration file is named\u00a0config<\/code>\u00a0and it is stored in\u00a0.ssh<\/code>\u00a0directory under user\u2019s home directory. The\u00a0~\/.ssh<\/code>\u00a0directory is automatically created when the user runs the ssh command for the first time.+<\/p>\n

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If you have never used the ssh\u00a0command<\/code>\u00a0first you\u2019ll need to create the directory using:<\/p>\n

mkdir -p ~\/.ssh && chmod 700 ~\/.ssh<\/code><\/p>\n<\/div>\n<\/div>\n<\/div>\n

By default the SSH configuration file may not exist so you may need to create it using the\u00a0touch command<\/a>:<\/p>\n

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touch ~\/.ssh\/config && chmod 600 ~\/.ssh\/config<\/span><\/code><\/pre>\n<\/div>\n
This file must be readable and writable only by the user, and not accessible by others:<\/p>\n
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chmod 700 ~\/.ssh\/config<\/span><\/code><\/pre>\n<\/div>\n
SSH Config File Structure and Patterns<\/a><\/h2>\n
The SSH Config File takes the following structure:<\/p>\n
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Host hostname1<\/span>\r\n    SSH_OPTION value<\/span>\r\n    SSH_OPTION value<\/span>\r\n\r\nHost hostname2<\/span>\r\n    SSH_OPTION value<\/span>\r\n\r\nHost *<\/span>\r\n    SSH_OPTION value<\/span><\/code><\/pre>\n<\/div>\n
The contents of the SSH client config file is organized into stanzas (sections). Each stanza starts with the\u00a0Host<\/code>\u00a0directive and contain specific SSH options that are used when establish connection with the remote SSH server.<\/p>\n
Indentation is not required, but is recommended since it will make the file easier to read.<\/p>\n
The\u00a0Host<\/code>\u00a0directive can contain one pattern or a whitespace-separated list of patterns. Each pattern can contain zero or more non-whitespace character or one of the following pattern specifiers:<\/p>\n