System administration

Initial setup (for Ubuntu distribution)

SSH keys

Create private/public SSH key file using 2048 bit encryption and with a comment. The command creates files under ~/.ssh folder.

$ ssh-keygen -b 2048 -C user@host.domain

SSH config for connection

The config file ~/.ssh/config stores information about various SSH connections, and allows the definition of hostname, username, ports, and other settings.

Host hostname1
    HostName hostname1.domain.com
    User username1
    Port 1234

Adding a user to sudoers list

#includedir /etc/sudoers.d should be at the end of /etc/sudoers file.

Create a file under this directory (i.e. localusers) and add entries.

jsmith ALL=(ALL) NOPASSWD:ALL would allow a user to sudo without entering a password.
jpocahontas ALL=(ALL) ALL would force password entry

Run $ chmod 0440 filename afterwards.

Enable color prompt

On Ubuntu distribution of GNU/Linux, you can uncomment force_color_prompt = yes line to use color prompts. The following is my personal favorite color configuration for the prompt.

PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u\[\033[01;30m\]@\[\033[00;36m\]\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '

Enable byobu

$ byobu-enable

Update .vimrc

syntax on
set noexpandtab
set wrap
set tabstop=4
set shiftwidth=4
set smartindent
set autoindent
set encoding=utf-8 fileencodings=
set mouse=a
set fo=cqlro
set tags=tags,../tags,../../tags,../../../tags,../../../../tags,../../../../../tags,../../../../../../tags
color elflord

" set foldmethod=marker
set foldmethod=indent
set foldnestmax=15
set nofoldenable
set foldlevel=1

" filetype plugin on
imap <c-k> <esc>:r! zdump GMT <bar> tail -c29 <bar> xargs -0 date +"\%-m/\%-d/\%-Y \%-l:\%M:\%S \%p" -d<enter>$i<right>

" PHP documenter script bound to Control-P
autocmd FileType php inoremap <C-p> <ESC>:call PhpDocSingle()<CR>i
autocmd FileType php nnoremap <C-p> :call PhpDocSingle()<CR>
autocmd FileType php vnoremap <C-p> :call PhpDocRange()<CR>

Set up environment for web development

Install the LAMP stack

$ sudo apt-get install tasksel

$ sudo tasksel install lamp-server

Install git and other PHP related extensions

$ sudo apt-get install git php5-mcrypt php5-xdebug php5-intl

.gitconfig

[core]
  editor = vim
  excludesfile = /home/mhan/.gitignore_global
# autocrlf = input
# safecrlf = true
[color]
  ui = always
[alias]
  co = checkout
  ci = commit
  st = status
  br = branch
  df = difftool
  hist = log --pretty=format:\"%C(yellow)%h %C(green)%ad %Creset| %s%C(red)%d %C(blue)[%an]\" --graph --date=short
  histall = log --pretty=format:\"%C(yellow)%h %C(green)%ad %Creset| %s%C(red)%d %C(blue)[%an]\" --graph --date=short --all
  hist10 = !git log --pretty=format:\"%C(yellow)%h %C(green)%ad %Creset| %s%C(red)%d %C(blue)[%an]\" --graph --date=short | head -n 10
  hist10all = !git log --pretty=format:\"%C(yellow)%h %C(green)%ad %Creset| %s%C(red)%d %C(blue)[%an]\" --graph --date=short --all | head -n 10
  type = cat-file -t
  dump = cat-file -p
  ignore = update-index --assume-unchanged
  track = update-index --no-assume-unchanged
  listignored = !git ls-files -v | grep -s ^'h ' | cut -b 1-2 --complement
[diff]
  tool = vimdiff
[difftool]
  prompt = false
[merge]
  defaultToUpstream = true

Change default shell

$ chsh

Edit passwd files

$ sudo vipw

Resources

Check disk space usage

You can check the file space usage with the command du.

$ du -h

Check disk space left

df is for checking the amount of disk space used and available on file systems.

$ df -h

User Accounts

Groups

Add a new group

$ sudo addgroup webdev

Delete a group

$ sudo delgroup webdev

Add a user to a group

$ sudo adduser username groupname

Set a directory writable by a certain group

Make /srv/www folder readable/writable/executable by dev group

$ sudo setfacl -d -m g:dev:rwx /srv/www

Add a user account

$ sudo useradd -d /home/jsmith -m jsmith -G webdev
$ sudo passwd jsmith

Delete a user account

Force removal and delete files

$ sudo userdel -fr username

or

$ sudo deluser -remove-home username

Lock or unlock a user account

$ sudo passwd -l username
$ sudo passwd -u username

Adding sudoers

A file can be added for groups of users or specific users to /etc/sudoers.d/ directory. This line would make someone a sudoer with no password requirement.

jsmith ALL=(ALL) NOPASSWD:ALL

If you want the user to type a password.

jsmith ALL=(ALL:ALL) ALL

Samba

Reset password for Samba server

$ samba-tool user setpassword administrator

OpenSSL

Creating self-signed certificates (usually for SSL connection)

$ sudo a2enmod ssl
$ sudo service apache2 restart

$ sudo mkdir /etc/apache2/ssl

$ sudo openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/apache2/ssl/apache.key -out /etc/apache2/ssl/apache.pem -outform PEM

Debian/Ubuntu-specific

Reconfigure console font

$ dpkg-reconfigure console-setup

Change time zone

$ dpkg-reconfigure tzdata