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Karl Morrison
Asked: 2017-08-03 05:46:51 +0800 CST

Create alias for ssh connecting

  • 772

I'd like to speed up connecting to specific servers.

I have the servers let's say:

123.123.123.1
123.123.123.2
123.123.123.3

I normally connect with the following:

ssh -p 12345 [email protected]

This is a pain because the only difference between the servers is the last number of the ip.

I tried the following code:

alias ssht='{ ip=$(cat -); ssh -p 12345 my_user@"123.123.123.$ip"; }<<<'

However I get an error:

karl@karls-laptop ~/scripts $ ssht 1
Pseudo-terminal will not be allocated because stdin is not a terminal.

Is there a way to get this working?

bash

5 Answers

  1. Use the intended way and write the options and aliases into ~/.ssh/config:

    Host 1
  Port 12345
  User my_user
  HostName 123.123.123.1

Host 2
  Port 12345
  User my_user
  HostName 123.123.123.2

    and so on...

    And then connect just using

    ssh 1
ssh 2
...
    • 61
  2. Best Answer

    This calls for a function -- simple and robust, whereas an alias in this case would be fragile.

    Something like this should do:

    function ssht () {
    [[ $1 =~ ^(1|2|3)$ ]] || { echo 'Not a valid last octet value !!' && return ;}
    ip=123.123.123.$1
    ssh my_user@"$ip" -p 12345
}

    The condition [[ $1 =~ ^(1|2|3)$ ]] makes sure you have entered one of 1, 2, 3 as first argument (any trailing argument is ignored).

    Now, you can give the desired last octet as the first argument:

    ssht 1
ssht 2
ssht 3

    Put this in your ~/.bashrc for having it available in any interactive session.

    • 20

  3. You can use patterns in ~/.ssh/config. From man ssh_config:

    PATTERNS
     A pattern consists of zero or more non-whitespace characters, ‘*’ (a
     wildcard that matches zero or more characters), or ‘?’ (a wildcard that
     matches exactly one character).  For example, to specify a set of
     declarations for any host in the “.co.uk” set of domains, the following
     pattern could be used:

           Host *.co.uk

     The following pattern would match any host in the 192.168.0.[0-9] network
     range:

           Host 192.168.0.?

    Combined with:

    HostName
    Specifies the real host name to log into.  This can be used to
    specify nicknames or abbreviations for hosts.  If the hostname
    contains the character sequence ‘%h’, then this will be replaced
    with the host name specified on the command line (this is useful
    for manipulating unqualified names).  The character sequence ‘%%’
    will be replaced by a single ‘%’ character, which may be used
    when specifying IPv6 link-local addresses.

    So, in your ~/.ssh/config, put:

    Host ?
    Hostname 123.123.123.%h
    Port 12345
    User my_user

    Then:

    $ ssh -v 1
OpenSSH_7.4p1, LibreSSL 2.5.0
debug1: Reading configuration data /home/muru/.ssh/config
debug1: /home/muru/.ssh/config line 41: Applying options for ?
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Connecting to 123.123.123.1 [123.123.123.1] port 12345.
debug1: connect to address 123.123.123.1 port 12345: Connection refused
ssh: connect to host 123.123.123.1 port 12345: Connection refused
    • 17

  4. Use a function instead :

    function ssht(){
 ssh -p 12345 [email protected].$1
}

    $ ssht 1
$ ssht 2
$ ...

    A better solution is to use a ssh config file:

    touch ~/.ssh/config

    with some lines similar to:

    Host some-name
    HostName 123.123.123.1
    User your_user
    Port 22

    You can also use ssh keys to improve the speed, finally you only run:

    ssh some-name

    and you are connected to that server.

    • 7

  5. You don't even need to use a name like ssht. Names starting with digits, even only digits are valid hostnames in ssh config file.

    Below works on Xubuntu Xenial

    Part of my ~/.ssh/config

    Host 1
        Hostname bastion.example.me
        User said
        Port 22
        IdentityFile ~/.ssh/id_rsa
        ForwardAgent yes

    Command I run (below I added -vv for verbose logging to STDOUT a.k.a your screen by default)

    ssh -vv 1

    Output

    OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g  1 Mar 2016
debug1: Reading configuration data /home/said/.ssh/config
debug1: /home/said/.ssh/config line 24: Applying options for 1
debug1: /home/said/.ssh/config line 540: Applying options for *
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "bastion.example.me" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to bastion.example.me [XXX.YYY.120.51] port 22.
debug1: Connection established.
debug1: identity file /home/said/.ssh/id_rsa type 1
debug1: key_load_public: No such file or directory
debug1: identity file /home/said/.ssh/id_rsa-cert type -1
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: Remote protocol version 2.0, remote software version OpenSSH_7.2p2 Ubuntu-4ubuntu2.2
debug1: match: OpenSSH_7.2p2 Ubuntu-4ubuntu2.2 pat OpenSSH* compat 0x04000000
debug2: fd 3 setting O_NONBLOCK
debug1: Authenticating to bastion.example.me:22 as 'said'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug2: local client KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,ext-info-c
debug2: host key algorithms: [email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected],ssh-ed25519,rsa-sha2-512,rsa-sha2-256,ssh-rsa
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected],aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected],zlib
debug2: compression stoc: none,[email protected],zlib
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug2: peer server KEXINIT proposal
debug2: KEX algorithms: [email protected],ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group14-sha1
debug2: host key algorithms: ssh-rsa,rsa-sha2-512,rsa-sha2-256,ecdsa-sha2-nistp256,ssh-ed25519
debug2: ciphers ctos: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: ciphers stoc: [email protected],aes128-ctr,aes192-ctr,aes256-ctr,[email protected],[email protected]
debug2: MACs ctos: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: MACs stoc: [email protected],[email protected],[email protected],[email protected],[email protected],[email protected],[email protected],hmac-sha2-256,hmac-sha2-512,hmac-sha1
debug2: compression ctos: none,[email protected]
debug2: compression stoc: none,[email protected]
debug2: languages ctos: 
debug2: languages stoc: 
debug2: first_kex_follows 0 
debug2: reserved 0 
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ecdsa-sha2-nistp256
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ecdsa-sha2-nistp256 SHA256:44tChrTUMwuRcOi6laiYlf6VM3qAD+PEn9EdNMribFw
debug1: Host 'bastion.example.me' is known and matches the ECDSA host key.
debug1: Found key in /home/said/.ssh/known_hosts:69
debug2: set_newkeys: mode 1
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug2: set_newkeys: mode 0
debug1: rekey after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS received
debug2: key: /home/said/.ssh/id_rsa (0x562c764294f0), explicit, agent
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<rsa-sha2-256,rsa-sha2-512>
debug2: service_accept: ssh-userauth
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering RSA public key: /home/said/.ssh/id_rsa
debug2: we sent a publickey packet, wait for reply
debug1: Server accepts key: pkalg rsa-sha2-512 blen 279
debug2: input_userauth_pk_ok: fp SHA256:KQNLYiJICyNbKmIxVVgc67RF+qRKjNi3w+0iXz/YDyk
debug1: Authentication succeeded (publickey).
Authenticated to bastion.example.me ([XXX.YYY.120.51]:22).
debug1: channel 0: new [client-session]
debug2: channel 0: send open
debug1: Requesting [email protected]
debug1: Entering interactive session.
debug1: pledge: network
debug1: client_input_global_request: rtype [email protected] want_reply 0
debug2: callback start
debug1: Requesting authentication agent forwarding.
debug2: channel 0: request [email protected] confirm 0
debug2: fd 3 setting TCP_NODELAY
debug2: client_session2_setup: id 0
debug2: channel 0: request pty-req confirm 1
debug2: channel 0: request shell confirm 1
debug2: callback done
debug2: channel 0: open confirm rwindow 0 rmax 32768
debug2: channel_input_status_confirm: type 99 id 0
debug2: PTY allocation request accepted on channel 0
debug2: channel 0: rcvd adjust 2097152
debug2: channel_input_status_confirm: type 99 id 0
debug2: shell request accepted on channel 0
Welcome to Ubuntu 16.04.2 LTS (GNU/Linux 4.8.0-42-lowlatency x86_64)
<TRUNCATED CUSTOM MOTD>
$

    Update - below is a hackish alternative solution, take it just for bashist exercise, maybe for quick and dirty stuff:

    alias ssht='f(){ ssh -p 22 [email protected].$@;unset -f f;}&&f'

    What it does

    • Create temporary function
    • Pass all arguments to it
    • Do the SSH connection
    • Once session ends, unset the function so it won't linger around
    • It can take additional arguments, meaning you can chain additional ssh options like tunneling (-L, -R, -D), verbose mode (-vv), no-TTY (-T) etc.

    For example I want to start a socks proxy with no terminal

    $ ssht 2 -vv -D 1080 -T
OpenSSH_7.2p2 Ubuntu-4ubuntu2.2, OpenSSL 1.0.2g  1 Mar 2016
debug1: Reading configuration data /home/said/.ssh/config
debug1: /home/said/.ssh/config line 540: Applying options for *
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: /etc/ssh/ssh_config line 19: Applying options for *
debug2: resolving "192.168.0.2" port 22
debug2: ssh_connect_direct: needpriv 0
debug1: Connecting to 192.168.0.2 [192.168.0.2] port 22.
debug1: Connection established.
<TRUNCATED>
Welcome to Linux Mint 18.1 Serena (GNU/Linux 4.4.0-81-generic x86_64)

 * Documentation:  https://www.linuxmint.com

98 packages can be updated.
0 updates are security updates.

    As you can see, no command prompt, it executed with -vv,-T,-D 1080 arguments.

    I can verify tunnel (basically SOCKS5 proxy) on my machine, too

    $ ss -ltnp | grep 1080
LISTEN     0      128    127.0.0.1:1080                     *:*                   users:(("ssh",pid=17038,fd=6))
    • 3