Archive for June, 2008

SSH and SCP with keys instead of passwords

Tuesday, June 10th, 2008

I’m writing about this bit of useful shell scripting, mostly so I know where to find it when I might need it again.

I needed to set up automatic backups using a shell script in Mac OS X, to copy (scp) tarballs from a mounted network drive on my Mac to a remote Linux environment. The only problem was the ssh authentication — the remote Linux server seemed to want a password every time. I remembered a friend of mine had done this a while back, and I started digging around. Here’s the summary of how you can set up your machine to be recognized by the remote machine,

1. On my Mac (Leopard), using the Terminal App, I ran,

ssh-keygen -t rsa

This outputs the following,

Generating public/private rsa key pair.
Enter file in which to save the key
(/Users/[username]/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):

I left that blank,

Enter same passphrase again:

Left that blank too,

Your identification has been saved in
/Users/[username]/.ssh/id_rsa.
Your public key has been saved in
/Users/[username]/.ssh/id_rsa.pub.
The key fingerprint is:
... finger print string here ...
[username]@[machine].local

Basically, this created two files in my user folder’s .ssh/ folder,

.ssh/id_rsa (This is the private key — guard it well)
.ssh/id_rsa.pub (This is the public key — pass it along)

2. I SSHed into the remote server to make sure my user account’s folder over there contained a .ssh/ folder. It didn’t, so I created one,

SSHed into remote server:

ssh user@remote

I was prompted for my password,

user@remote's password:

Once I was in, I created the .ssh/ folder,

mkdir .ssh

Then I exited the remote server.

3. Then I had to transfer my public key over to the remote server. I ran the following from my home folder,

ssh user@remote "cat >> .ssh/authorized_keys"
< .ssh/id_rsa.pub

Again, I was prompted for my password,

user@remote's password:

When it was done adding my public key, it logged me out.

Now when I run,

ssh user@remote

I no longer get prompted for a password, I just go right in. This means my backup script, using scp, can run as a cron job.

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JetBlue accross the country with demons

Thursday, June 5th, 2008

Our first mistake was to change our flight from a Monday to Wednesday. Nina got an ear infection during our trip to Baltimore for a wedding, and the antibiotic she started gave her diarrhea — a dreaded but expected side effect. We thought it would be a good idea to delay our departure by two days, hoping she would start to feel better, and that her gastrointestinal system would get back to normal.

So we moved our departure by two days, on JetBlue 317. Of course, there were no longer any seats available that were together. In fact, we ended up with three middle seats, in three different rows. The helpful woman on the reservation phone line at JetBlue told me not to worry because the people at the airport’s check-in counter have all the power to move people around. We would be assigned seats next to each other for sure, as long as we got to the airport more than 2 hours early.

We left for the airport ridiculously early, and arrived at International Airport Dulles at 2pm, for a 4:45pm departure. That was our second mistake. The not so friendly JetBlue agent at the check-in counter basically told me we’re out of luck. We were stuck with our middle seats… Unless the people at the gate might be able to help. When we got to the gate, after a mad scramble through security with a tired toddler, a crazed little girl who just wanted to go run around outside and play, our hopes of adjoining seats were once again dashed by another not so friendly JetBlue gate agent.

We finally boarded the plane at 5:30pm, after three and a half hours in the airport — with two demons at our sides. Since we were traveling with demons, we got to pre-board. We got onto the plane and waited for the rest of the passengers to arrive, in particular, those in the aisle and window seats in our three rows. The first aisle seat woman said no to a seat swap. We were down to two possible rows. The second aisle man emphatically refused. We were down to our last row. Fortunately, the window and aisle men for our last row came and agreed to a swap. May good karma shine upon them, at least for a while.

With that stressful ordeal over, we were ready to face our third mistake. Nina is too crazy to take on as a lap child.

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