Recently, a SSH client bug was discovered that could let the server read client private keys in some situations.

If you’re affected, then follow these steps. SSH regulars will be familiar with most of the commands used.

If you use public key authentication

If you do use keys to authenticate, you should regenerate them. Start by backing up your old key. Assuming it’s at the default location, just use-

$ mv ~/.ssh/id_rsa ~/.ssh/id_rsa.old
$ mv ~/.ssh/id_rsa.pub ~/.ssh/id_rsa.pub.old

Next, create or edit ~/.ssh/config, and add the following line. This disables the roaming feature, which was part of the problem:

UseRoaming no

Generate new keys-

$ ssh-keygen 
Generating public/private rsa key pair.
Enter file in which to save the key (/home/example/.ssh/id_rsa): 
Enter passphrase (empty for no passphrase): 
Enter same passphrase again: 
Your identification has been saved in /home/example/.ssh/id_rsa.
Your public key has been saved in /home/example/.ssh/id_rsa.pub.

Now copy the new public key over, using the old keys. You would normally use ssh-copy-id, but it adds keys rather than replacing them, which is why we need to do it manually-

scp -i ~/.ssh/id_rsa.old ~/.ssh/id_rsa.pub user@example.com:/home/user/id_rsa.pub.new

SSH in with the old key:

ssh -i ~/.ssh/id_rsa.old

Replace all current authorized keys with the newly generated one:

mv -f id_rsa.pub.new ~/.ssh/authorized_keys
chmod 600 ~/.ssh/authorized_keys

Logout, log back in with the new key to make sure it works, and you’re done.

If you don’t use public keys

If you don’t use keys for login, now could be a good time to start. Public-key authentication provides much stronger protection from brute force attacks, and also prevents the need for the server to be sent your password each time you log in.

Create or edit ~/.ssh/config as above, and make sure it contains this line-

UseRoaming no

Generate a keypair and add your public key to the server-

ssh-keygen
ssh-copy-id user@example.com

Test it out-

ssh user@example.com

At his point, you should disable password-based authentication in OpenSSH server. If you don’t control the server, then just set a good random password for your account to prevent it being brute-orced:

openssl rand -base64 32
cat /dev/urandom | head -c32 | base64

Set it on your account:

passwd

Update 2017-10-22: Updated to correct errors in the commands.

This post covers some LaTeX examples that I recently assembled for print-outs where multiple pages-per-sheet will be printed for cutting.

First up, an example file. This is a document filled with random text, on C6 paper.

\documentclass{article}

\usepackage[c6paper]{geometry}
\usepackage{lipsum}

\begin{document}
\section*{Lorem Ipsum}
\lipsum[1-11]
\end{document}

It renders like so (click for PDF):

1×1 arrangement

Using the crop package, you can wrap the output pages of your document in larger pages. Using the \includepdf macro, these pages can be sourced from our example document.

This example simply renders the document on larger pages, with crop marks displayed at the document edges.

\documentclass{article}
\usepackage{pdfpages}
% Sum of dimensions of the pages. We are displaying 1x1 C6 (114 mm x 162mm) pages, which is where 114x162 comes from.
\usepackage[paperheight=162mm,paperwidth=114mm]{geometry}

% Include print/output paper size and orientation here, A4 portrait in this example (use 'landscape' option for landscape)
\usepackage[axes,cam,a4,pdftex,center]{crop}

\begin{document}

% Restrict page range, and set arrangement of pages per sheet here.
\includepdf[pages=-,nup=1x1,noautoscale]{book-pages.pdf}

\end{document}

This renders a single C6 page on A4 like this (click image for PDF):

2×1 arrangement

To lay out two images side-by-side, we need to specify the size of the document we’re wrapping (which will be twice as wide as a single C6 page, and the height of a single C6 page), and also change the orientation of the outer paper to Landscape.

The LaTeX code is:

\documentclass{article}
\usepackage{pdfpages}
% Sum of dimensions of the pages. We are displaying 2x1 C6 (114 mm x 162mm) pages, which is where 228x162 comes from.
\usepackage[paperheight=162mm,paperwidth=228mm]{geometry}

% Include print/output paper size and orientation here, A4 landscape in this example.
\usepackage[axes,cam,a4,landscape,pdftex,center]{crop}

\begin{document}

% Restrict page range, and set arrangement of pages per sheet here.
\includepdf[pages=-,nup=2x1,noautoscale]{book-pages.pdf}

\end{document}

Which renders as (click for PDF):

2×2 arrangement

In a similar way, we can slot four portrait C6 pages on to a piece of A4 portait paper like so:

\documentclass{article}
\usepackage{pdfpages}
% Sum of dimensions of the pages. We are displaying 2x2 C6 (114 mm x 162mm) pages, which is where 228x324 comes from.
\usepackage[paperheight=324mm,paperwidth=228mm]{geometry}

% Include print/output paper size and orientation here, A3 portrait in this example (use 'landscape' option for landscape)
\usepackage[axes,cam,a3,pdftex,center]{crop}

\begin{document}

% Restrict page range, and set arrangement of pages per sheet here.
\includepdf[pages=-,nup=2x2,noautoscale]{book-pages.pdf}

\end{document}

This renders as:

More complex arrangement

Ok, so all of the above setups had one thing in common: 2 or fewer items on each side, meaning that the half-way axis lines could be used to show where each page ends.

If you are printing many small items, you might fit more than two in a direction, and need to add more axis lines so that you know where to cut!

Here is an example PDF which creates tiny name tags:

\documentclass{article}
% Custom page size
\usepackage[margin=4mm,paperheight=30mm,paperwidth=60mm]{geometry}

% Macro for a name tag
\newcommand{\tag}[2]{\begin{center}~\\\textbf{\Large#1}\\~\\\em{#2}\end{center}\clearpage}

\begin{document}

% Make some name tags for a conference
% Names generated via www.generatedata.com/
\tag{Flynn Craig}{ExampleCorp}
\tag{Daniel Cash}{ExampleCorp}
\tag{Griffith Durham}{ExampleCorp}
\tag{Sean Washington}{ExampleCorp}
\tag{James Simon}{ExampleCorp}
\tag{Aidan Cotton}{ExampleCorp}
\tag{Wing Sanders}{ExampleCorp}
\tag{Dean Wilcox}{ExampleCorp}
\tag{Jerome Flynn}{FooCorp}
\tag{Leonard Steele}{FooCorp}
\tag{Zane Pratt}{FooCorp}
\tag{Andrew Hartman}{FooCorp}
\tag{Roth Mccullough}{FooCorp}
\tag{Fritz Taylor}{Quux Ltd}
\tag{Beau Bray}{Quux Ltd}
\tag{Duncan Hampton}{Quux Ltd}
\tag{Daquan Witt}{Quux Ltd}
\tag{Wylie Heath}{Quux Ltd}
\tag{Thaddeus Payne}{Quux Ltd}
\tag{Carson Ayala}{Quux Ltd}
\tag{Oleg Olson}{Quux Ltd}
\tag{Herrod Gillespie}{Bar University}
\tag{Jonas Wyatt}{Bar University}
\tag{Mannix Patrick}{Bar University}
\tag{Cain Ferguson}{Bar University}
\tag{Nasim Mendez}{Bar University}
\tag{Emery Bennett}{Bar University}
\tag{Oscar Bennett}{Bar University}
\tag{William Neal}{Bar University}
\tag{Dieter Cochran}{Bar University}
\tag{Bert Schultz}{Bar University}

\end{document}

The above example renders like this (click image for PDF):

Now, the trick is that crop is hard-coded to show axis lines only at the half-way points, so take a copy of crop.sty called crop-3x7.sty and find this block:

\newcommand*\CROP@marks{%
    \CROP@setmarkcolor
    \CROP@user@b
    \CROP@ulc\null\hfill\CROP@@@info\CROP@upedge\hfill\null\CROP@urc
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@llc\null\hfill\CROP@loedge\hfill\null\CROP@lrc
}

The block uses \vfill and \hfill to make even spaces.

Edit the file to include more axis lines, like so:

%% 'crop-3x7' is not a real package for general use, it is an example only!
%%
%% It is a modified version of the 'crop' package, for rendering
%% additonal axis marks as cutting aids.
...
% Changed package name here-
\ProvidesPackage{crop-3x7}[2016/01/03 v2.0 crop marks 3x7 (mf)]
...
\newcommand*\CROP@marks{%
    % Changed from one axis on each side to 2 axes on top/lower edge, 6 on each side, for printing 3x7 panels per this example. 
    \CROP@setmarkcolor
    \CROP@user@b
    \CROP@ulc\null\hfill\CROP@@@info\CROP@upedge\hfill\CROP@upedge\hfill\null\CROP@urc
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@ledge\hfill\CROP@redge
    \vfill
    \CROP@llc\null\hfill\CROP@loedge\hfill\CROP@loedge\hfill\null\CROP@lrc
}

Now simply prepare a page which shows a 3×7 grid of tags, using the same rules as before, and our modified crop-3x7.sty:

\documentclass{article}
% This file demonstrates the use of a customisation to the 'crop' package to render additional axes for cutting up small name labels.

\usepackage{pdfpages}
% Sum of dimensions of the pages. We are displaying 3x7 small tags (60 x 30 mm) to a page, which is where 180x210 comes from.
\usepackage[paperheight=210mm,paperwidth=180mm]{geometry}

% Include print/output paper size and orientation here, A3 portrait in this example (use 'landscape' option for landscape)
\usepackage[axes,cam,a4,pdftex,center]{crop-3x7}

\begin{document}

% Restrict page range, and set arrangement of pages per sheet here.
\includepdf[pages=-,nup=3x7,noautoscale]{labels.pdf}

\end{document}

Render the document, and see the small dashes on the sides which will show you where to cut:

The code

Full source for all of the linked files can be found in my tex-examples repository on GitHub.

If you just installed Debian, you might notice that one Linux staple, sudo is not installed by default. Here is the quick way to add it, and set yourself up as an administrative user.

1. Install sudo, using the su command to elevate privileges.

bob$ su
Password: 
root# apt-get install sudo

2. Make yourself an administrator. The default /etc/sudoers file contains this line:

# Allow members of group sudo to execute any command
%sudo	ALL=(ALL:ALL) ALL

So simply add your account (‘bob‘ in this example) to the sudo group:

root# usermod -a -G sudo bob

3. Log out and back in again, in order to apply changes to your group membership.

bob$ groups
bob cdrom floppy sudo audio dip video plugdev netdev lpadmin scanner bluetooth
bob$ sudo echo test
[sudo] password for bob: 
test