Skip to main content

SSH Daemon on a Mac

A Mac is a weird thing that doesn't always know whether it wants to be BSD or Linux.

Enable Remote Login
You should only need to enable remote login:
$ sudo systemsetup -setremotelogin on

If the above doesn't work, here is the magical incantation to start a SSH Server:
$ sudo launchctl start /System/Library/LaunchDaemons/ssh.plist

One can then check it with a Telnet client:
$ telnet localhost ssh 
 Trying ::1... 
 Connected to localhost. Escape character is '^]'. 
 SSH-2.0-OpenSSH_6.2 ^] 
 telnet> q 
 Connection closed. 

Now you can use scp and ssh from another machine on the LAN, but one needs to know what the IP address is:
$ ifconfig en0 | grep inet 
inet6 fe80::5626:96ff:fece:371f%en0 prefixlen 64 scopeid 0x4 
inet 192.168.1.5 netmask 0xffffff00 broadcast 192.168.1.255

Run SSHD On A Different Port

If you want to allow internet access to your Mac and don't want to be bothered by script kiddies all the time, then you need to change sshd to a different port. 

The Mac launchctl system seems to ignore the /etc/sshd_conf file.  The only way that I could convince it to run on a different port, was by editing the /etc/services file and then reloading sshd with launchctl.

$ sudo launchctl unload /System/Library/LaunchDaemons/ssh.plist
$ sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist
 
This will automatically change the firewall port also.  


SSHD Won't Run After Reboot
Verify that /System/Library/LaunchDaemons/ssh.plist exist and make sure <key>Disabled</key> is not set to <true/>. Also make sure it starts on boot every time with <key>RunAtLoad</key> set to <true/>:
....
<dict>
    <key>Disabled</key>
    <false/>
    <key>RunAtLoad</key>
    <true/>
    <key>Label</key>
    <string>com.openssh.sshd</string>
....

Then run the following to make sure the new settings stick:

$ sudo launchctl load -w /System/Library/LaunchDaemons/ssh.plist


La voila!


Labels:

Comments

Post a Comment

On topic comments are welcome. Junk will be deleted.

Popular posts from this blog

Parasitic Quadrifilar Helical Antenna

This article was reprinted in OSCAR News, March 2018:  http://www.amsat-uk.org If you want to receive Satellite Weather Pictures , then you need a decent antenna, otherwise you will receive more noise than picture. For polar orbit satellites, one needs an antenna with a mushroom shaped radiation pattern .  It needs to have strong gain towards the horizon where the satellites are distant, less gain upwards where they are close and as little as possible downwards, which would be wasted and a source of noise.  Most satellites are spin stabilized and therefore the antenna also needs circular polarization, otherwise the received signal will flutter as the antennas rotate through nulls. The helical antenna, first proposed by Kraus in 1948, is the natural solution to circular polarized satellite communications.  It is a simple twisted wire - there seems to be nothing to it.  Various papers have been published on helix antennas, so the operation is pretty well ...
2 comments
Read more

To C or not to C, That is the Question

As most would know, the Kernighan and Ritchie C Programming Language is an improved version of B, which is a simplified version of BCPL, which is derived from ALGOL, which is the Ur computer language that started the whole madness, when Adam needed an operating system for his Abacus, to count Eve's apples in the garden of Eden in Iraq.  The result is that C is my favourite, most hated computer language , which I use for everything. At university, I learned FORTRAN with punch cards on a Sperry-Univac, in order to run SPICE, to simulate an operational amplifier.  Computers rapidly lost their glamour after that era! Nobody taught me C.  I bought the book and figured it out myself. Over time, I wrote a couple of assemblers, a linker-locator, various low level debuggers and schedulers and I even fixed a bug in a C compiler - not because I wanted to, but because I had to, to get the job done!   Much of my software work was down in the weeds with DSP and radio modems...
Post a Comment
Read more

Unlock CRA PDF Forms

Unlock Canada Revenue Agency PDF Forms It appears that there is a relatively new PDF feature to prevent casual copying and saving of a file and that some programs save PDF files with these foolish features active by default.  Many forms from the Canada Revenue Agency are locked in this way, which makes it difficult to do one's taxes, since one can fill the form, but cannot save it.  One can only print the form.  It should be possible to print to a file or export it to a new PDF file, but it is far better to reset the annoying anti-taxpayer flags, since the 'printed' form cannot be edited easily any more and I always manage to make a mistake or three that need to be corrected after review. If there is a Linux (virtual) machine handy, install qpdf and use it to reset the silly flags: $ su - password # dnf update # dnf install qpdf # exit $ qpdf --decrypt lockedfile.pdf unlockedfile.pdf One doesn't need a password to unlock these flags, so the fix is instant. La voila! He...
Post a Comment
Read more