ssh

Coping files between Linux servers – using SCP

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For a few years now I keep catching myself transferring files between Linux servers, in a silly way…

What I mean is using somthing like ftp, or copying to my desktop and then up to the other server – all hassle (and in the case of ftp – inherently insecure).  Why do I do this?  Well not because there’s no alternative, but because I can never easily remember how to do it the “proper” way.

So how to do it – simply use SCP, this copies a file using SSH and so is more secure (we trust SSH right?), even better I’ve never had a server which doesn’t support it out of the box.

Right so how to transfer one file:

scp /sourcedir/filename.extension user@serverip:/destinationdir/

It’s quite simple really – if you run SSH on an abnormal port (you really should it cuts down the attacks) then you can specify the port like this:

scp -P 2100 /sourcedir/filename.extension user@serverip:/destinationdir/

Also, if you want to transfer multiple files (e.g. all the images in a directory) then you can just use wildcards – like below:

scp -P 2100 /sourcedir/*.extension user@serverip:/destinationdir/

rm Argument list too long.. Linux Huh? moment.

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I recently had a little problem when deleting a store of spam e-mails off one of my personal servers.

Basically entering the standard death defying command of “rm -Rfv *” while in a directory (this will delete everything recursively – have fun), the system responded “Argument list too long” – cue the first “huh?” moment – I’ve used the command for years and years, never had a problem.

I did “man rm” to check I hadn’t had a “moment” and forgotten how to use it – nope.. . A little trawling came up with several people with the same problem but no really practical solutions.  The problem occurs when you have too many files for the built in systems used by the rm command in the kernel – these are pretty old so have some limits that you don’t expect! – you can do this:

rm -Rfv a* then rm -Rfv A* –  these deletes all files starting with a or A etc.. – very long and rather silly – so after thinking and thinking and muttering an old command came to mind 🙂  using a combination of find and xargs you can pipe a file on at a time so here we go – my favoured solution:

find . -name * | xargs rm -fv

This works fine – I suspect it will have a limit somewhere, but my server hasn’t hit it yet!

Putty – for SSH

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Ok – I use 3 distinctly different operating systems routinely.

I have windows XP – this is on my laptop and also have a copy on my desktop – though this rarely runs it now.

I have ubuntu (kubuntu) on my desktop – this is nearly always on and is great.

I then have a Mac in the office at work – running Mac OS X.

generally apart from keyboard issues (as i don’t have a Mac Keyboard so sometimes the mappings go wonky) – the Mac is fine – no probs, but in order to access SSH the Mac just doesn’t have anything to touch Putty.

Putty is a very well known and very popular SSH client – I’ve been using it since around 2003 – maybe earlier.  It exists for windows and this appears to be where it is primarily developed for – and it’s great – never seen a better SSH client – does what’s needed – nice and clean, lets you save session data etc…

It exists for Linux – so I have in it my ubuntu install – don’t recall how I got it – but it’s pretty much like the windows client – few little quirks but it’s putty and i can use it.
But when it comes to the Mac – I’ve hunted – searched – tried someones build – didn’t work – got the source – can’t compile it!  Why does no real equivalent of Putty exist  – theres a few that pretend to be – buth when you are administrating multiple servers they just don’t quite cut it!

The problem is it’s not just Putty – theres a handful of programs that seem to be available on “free” operating systems like ubuntu which help people who have come from windows – and who – to be honest – like to use a graphical interface sometimes – which just aren’t available on the Mac – I am sure this works the other way – problem is the Apple want the Mac to be more mainstream and whilst they are making progress – it’s just not there yet…

P.s. I am sure I will rant about how useless windows is – and ubuntu at some point – in fact I feel a Ubuntu rant coming along soon…..