SSH client configuration files allow us to connect to servers with pre-configured commands. This saves time by avoiding typing each SSH command parameter when logging into a remote machine and executing commands on a remote device.<\/p>\n\n\n\n
If you are regularly connecting to multiple remote systems over SSH, 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.<\/p>\n\n\n\n
To begin, ensure that you have SSH installed on your machine. The\u00a0 Next, create the SSH config file with the following command and save it in your home directory\u00a0 This file must be readable and writable only by the user and not accessible by others:<\/p>\n\n\n\n Typically, when connecting to a remote server via SSH, you would specify the remote user name, hostname, and port. For example, to log in as a user named\u00a0brice\u00a0to a host called\u00a0 To connect to the server using the same options as provided in the command above, simply by typing\u00a0 Now when you type\u00a0 Now let\u00b4s define multiple entries in the config file. Here is an example file showing numerous hosts:<\/p>\n\n\n\n The example file defines two Host entries in the config file and separates them using an empty line. It’s worth noting that the configuration file can have many entries<\/em><\/strong>. If that is the case, simply use a blank line to separate them.<\/p>\n\n\n\n Use the specified Host identifier and run the following commands to connect to your remote server:<\/p>\n\n\n\n The SSH client parses the config file and compares the defined Host identifier\u2019s values with the provided identifier. If they match, the configuration loads.<\/p>\n\n\n\n Next, let\u2019s see what the various parameters in the config file do.<\/p>\n\n\n\n <\/p>\n\n\n\n The ssh client reads its configuration in the following precedence order:<\/p>\n\n\n\n If you want to override a single option, you can specify it on the command line. For example, if you have the following definition:<\/p>\n\n\n\n and you want to use all other options but to connect as user\u00a0 When you type\u00a0 The full list of options used when we type\u00a0 When running\u00a0 SSH client configuration files allow us to connect to servers with pre-configured commands. This saves time by avoiding typing each SSH command parameter when logging into a remote machine and executing commands on a remote device. If you are regularly connecting to multiple remote systems over SSH, you\u2019ll find that remembering all of the remote […]<\/p>\n","protected":false},"author":1,"featured_media":1910,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":[],"categories":[212,31],"tags":[544,291,241],"_links":{"self":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/1905"}],"collection":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/comments?post=1905"}],"version-history":[{"count":2,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/1905\/revisions"}],"predecessor-version":[{"id":1911,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/posts\/1905\/revisions\/1911"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/media\/1910"}],"wp:attachment":[{"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/media?parent=1905"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/categories?post=1905"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/nguenkam.com\/blog\/index.php\/wp-json\/wp\/v2\/tags?post=1905"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}.ssh<\/em><\/strong><\/code>\u00a0directory ist usualy located under the user\u2019s home<\/em><\/strong> directory. It \u00a0is automatically created when the user runs the\u00a0ssh<\/code><\/a>\u00a0command for the first time. If the directory doesn\u2019t exist on your system, create it using the command below:<\/p>\n\n\n\nmkdir -p ~\/.ssh && chmod 700 ~\/.ssh<\/code><\/pre>\n\n\n\n.ssh<\/code>\u00a0folder.<\/p>\n\n\n\n$ touch \/home\/yourusername\/ .ssh\/config\n\/\/Or\ntouch ~\/.ssh\/config<\/code><\/pre>\n\n\n\nchmod 600 ~\/.ssh\/config \n\/\/or\nchmod 700 ~\/.ssh\/config<\/code><\/pre>\n\n\n\nCreating a connection<\/h4>\n\n\n\n
dev.example.com<\/code>\u00a0on port\u00a0116\u00a0from the command line, you would type:<\/p>\n\n\n\nssh brice@dev.example.com -p 116<\/code><\/pre>\n\n\n\nssh dev<\/code>, put the following lines to your\u00a0\"<\/code>~\/.ssh\/config<\/code>\u00a0<\/em>” <\/strong>file:<\/p>\n\n\n\nHost dev\r\n HostName dev.example.com\r\n User brice\r\n Port 116\r\n<\/code><\/pre>\n\n\n\nssh dev<\/code>, the ssh client will read the configuration file and use the connection details that are specified for the\u00a0dev<\/code>\u00a0host:<\/em><\/p>\n\n\n\nssh dev<\/code><\/pre>\n\n\n\nHost newServer\r\n HostName newServer.url\r\n User adminuser\r\n Port 2222\r\n IdentityFile ~\/.ssh\/id_rsa.key\r\n\r\nHost anotherServer.tld\r\n HostName anotherServer.url\r\n User mary\r\n Port 2222<\/code><\/pre>\n\n\n\nConnecting<\/h4>\n\n\n\n
$ ssh newServer\r\n$ ssh anotherServer.tld<\/code><\/pre>\n\n\n\nHostname<\/strong><\/span><\/code>\u00a0specifies the actual hostname. You can also use numeric IP addresses. You can skip this if the\u00a0Host identifier<\/code><\/span>\u00a0already identifies the hostname you want to connect.<\/li>Host<\/strong><\/span><\/code>\u00a0defines the host or hosts to which the configuration section applies. You can use a single asterisk (*) as a pattern to provide global defaults for all hosts.<\/li>Port<\/strong><\/span><\/code>\u00a0is where your remote SSH server is listening for connections. It defines the remote host’s connection port number, which is\u00a022<\/code>\u00a0by default.<\/li>User<\/strong><\/span><\/code>\u00a0defines the username for the SSH connection.<\/li>IdentityFile<\/code>\u00a0<\/strong><\/span>specifies the file containing the user\u2019s DSA, ECDSA or DSA authentication identity. For SSH protocol version 1, the default is\u00a0~\/.ssh\/identity<\/code>. For version 2, the defaults are\u00a0~\/.ssh\/id_ecdsa<\/code>\u00a0and\u00a0~\/.ssh\/id_rsa<\/code>.<\/li><\/ul>\n\n\n\nOverride SSH Config File Option\u00a0#<\/a><\/h4>\n\n\n\n
~\/.ssh\/config<\/code>.<\/strong><\/em><\/li>\/etc\/ssh\/ssh_config<\/code><\/strong>.<\/em><\/li><\/ol>\n\n\n\nHost dev\r\n HostName dev.example.com\r\n User brice\r\n Port 116\r\n<\/code><\/pre>\n\n\n\nroot<\/strong><\/em><\/code>\u00a0instead of\u00a0brice<\/strong><\/em>\u00a0simply specify the user on the command line:<\/p>\n\n\n\nssh -o \"User=root\" dev<\/code><\/pre>\n\n\n\nShared SSH Config File Example<\/h4>\n\n\n\n
Host targaryen\r\n HostName 192.168.1.10\r\n User daenerys\r\n Port 7654\r\n IdentityFile ~\/.ssh\/targaryen.key\r\n\r\nHost tyrell\r\n HostName 192.168.10.20\r\n\r\nHost martell\r\n HostName 192.168.10.50\r\n\r\nHost *ell\r\n user oberyn\r\n\r\nHost * !martell\r\n LogLevel INFO\r\n\r\nHost *\r\n User root\r\n Compression yes\r\n<\/code><\/pre>\n\n\n\nssh targaryen<\/code><\/span><\/em>, the ssh client reads the file and apply the options from the first match, which is\u00a0Host targaryen<\/code>.<\/span><\/em> Then it checks the next stanzas one by one for a matching pattern. The next matching one is\u00a0Host * !martell<\/em><\/span><\/code>\u00a0(meaning all hosts except\u00a0martell<\/code>), and it will apply the connection option from this stanza. The last definition\u00a0Host *<\/em><\/span><\/code>\u00a0also matches, but the ssh client will take only the\u00a0Compression<\/span><\/em><\/code>\u00a0option because the\u00a0User<\/span><\/code>\u00a0option is already defined in the\u00a0Host targaryen<\/code>\u00a0<\/span><\/em>stanza.<\/p>\n\n\n\nssh targaryen<\/code>\u00a0<\/strong><\/em><\/span> will be then:<\/p>\n\n\n\nHostName 192.168.1.10\r\nUser daenerys\r\nPort 7654\r\nIdentityFile ~\/.ssh\/targaryen.key\r\nLogLevel INFO\r\nCompression yes<\/code><\/pre>\n\n\n\nssh tyrell<\/span><\/em><\/code>\u00a0the matching host patterns are:\u00a0Host tyrell<\/code> ,<\/span><\/em>\u00a0 Host *ell<\/span><\/em><\/code>,\u00a0 Host * !martell<\/code><\/span><\/em>\u00a0and\u00a0Host *<\/span><\/em><\/code>. The options used in this case are:<\/p>\n\n\n\nHostName 192.168.10.20\r\nUser oberyn\r\nLogLevel INFO\r\nCompression yes<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"