Marcus Hall

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====== Disk Usage Analyzer ======

From: http://www.makeuseof.com/tag/how-to-analyze-your-disk-usage-pattern-in-linux/

<code>
Formerly known as Baobab, Disk Usage Analyzer is, as you might have guessed, another visual tool. 
Rather than the block-based approach of QDirStat, this utility offers a radial treemap pie chart 
as a live illustration of disk usage. You’ll find this in the right-hand pane; on the left, a 
list of the contents of the currently selected directory.
</code>

====== unprivileged user ======

From: http://unix.stackexchange.com/questions/22275/how-to-create-an-unprivileged-user-in-centos

<code>
useradd (which is the actual binary the runs when you call adduser, it just behaves differently. See here about that.) has an flag -r 
</code>

From: man: useradd

<code>
-r, --system
Create a system account. 

System users will be created with no aging information in /etc/shadow, and their numeric 
identifiers are chosen in the SYS_UID_MIN-SYS_UID_MAX range, defined in /etc/login.defs, 
instead of UID_MIN-UID_MAX (and their GID counterparts for the creation of groups). 

Note that useradd will not create a home directory for such an user, regardless of the 
default setting in /etc/login.defs (CREATE_HOME). You have to specify the -m options if 
you want a home directory for a system account to be created.
</code>

====== Good Description of systemd ======

From: http://0pointer.de/blog/projects/systemd.html

<code>
Process Identifier 1

On every Unix system there is one process with the special process identifier 1. It is started 
by the kernel before all other processes and is the parent process for all those other processes 
that have nobody else to be child of. Due to that it can do a lot of stuff that other processes 
cannot do. And it is also responsible for some things that other processes are not responsible 
for, such as bringing up and maintaining userspace during boot.

For a fast and efficient boot-up two things are crucial:

    To start less.
    And to start more in parallel.
</code>


====== How Do I Convert A SysV Init Script Into A systemd Service File ======

From: http://0pointer.de/blog/projects/systemd-for-admins-3.html

create a systemd process service

<code>
And that's already it. The entire remaining content of this 115-line shell script is simply boilerplate or otherwise redundant code: code that deals with synchronizing and serializing startup (i.e. the code regarding lock files) or that outputs status messages (i.e. the code calling echo), or simply parsing of the verbs (i.e. the big case block).

From the information extracted above we can now write our systemd service file:

[Unit]
Description=Daemon to detect crashing apps
After=syslog.target

[Service]
ExecStart=/usr/sbin/abrtd
Type=forking

[Install]
WantedBy=multi-user.target
</code>
====== systemd-ui ======

From: http://vazhavandan.blogspot.com/2013/04/graphical-frontend-for-systemd-on.html

graphical frontend for systemd

<code>
zypper install systemd-ui

systemadm

</code>


From: https://www.freedesktop.org/wiki/Software/systemd/

<code>
systemd is a suite of basic building blocks for a Linux system. It provides a system and 
service manager that runs as PID 1 and starts the rest of the system. systemd provides 
aggressive parallelization capabilities, uses socket and D-Bus activation for starting 
services, offers on-demand starting of daemons, keeps track of processes using Linux control 
groups, supports snapshotting and restoring of the system state, maintains mount and 
automount points and implements an elaborate transactional dependency-based service 
control logic. systemd supports SysV and LSB init scripts and works as a replacement 
for sysvinit. Other parts include a logging daemon, utilities to control basic system 
configuration like the hostname, date, locale, maintain a list of logged-in users and 
running containers and virtual machines, system accounts, runtime directories and 
settings, and daemons to manage simple network configuration, network time synchronization, 
log forwarding, and name resolution. See Lennart's blog story for a longer introduction, and 
the three status updates since then. Also see the Wikipedia article. If you are wondering 
whether systemd is for you, please have a look at this comparison of init systems by one 
of the creators of systemd. 
</code>

====== difference between service and systemctl ======

From: http://forums.fedoraforum.org/showthread.php?t=261945

<code>
service operates on the files in /etc/init.d and was used in conjunction with the old 
init system. systemctl operates on the files in /lib/systemd . If there is a file for 
your service in /lib/systemd it will use that first and if not it will fall back to the 
file in /etc/init.d
</code>

=== systemctl ===

From: http://fedoraproject.org/wiki/Systemd

From: http://crashmag.net/useful-systemd-commands

=== List the current run level ===
<code>
systemctl list-units --type=target
</code>
====== Hardware Info ======

    Grub at higher resolutions?
    The best achieved is, with vga=0x346
    Mode 0x0346: 1400x1050 (+5632), 24 bits
    See what's available with cmd
    hwinfo --framebuffer
    also available,
    Mode 0x0343: 1400x1050 (+1408), 8 bits
    Mode 0x0345: 1400x1050 (+2816), 16 bits 

====== UNetbootin - Homepage and Downloads ======

From: http://unetbootin.sourceforge.net/

    UNetbootin allows you to create bootable Live USB drives for Ubuntu, 
    Fedora, and other Linux distributions without burning a CD. It runs on 
    Windows, Linux, and Mac OS X.
    
    Note that resulting USB drives are bootable 
    only on PCs (not on Macs).

====== Compression ======

From: http://www.littleigloo.org/linux/how-to/uncompress-linux-files.html

    Xz is becoming rather popular now-days. For example the official Gnome FTP
    software archive is now offering for download Xz compressed archives rather
    than Gzip ones


====== OpenSuse Reference ======

From: http://opensuse-guide.org/index.php

    The purpose of this guide is to provide new users with everything
    they need to know to get started using openSUSE as a home user/small
    office desktop operating system - quickly and easily. 

====== Recover - Reset Lost Password ======

  * Stop Grub Boot by Down arrow key then select default boot option
  * Type **"e"**
  * add parameter **"init=/bin/bash"**
  * **Ctrl-x** to run
  * after boot **"passwd"**
  * enter new password and confirm
  * **QED**

====== DRBD ======

From: http://www.drbd.org/download/mainline/

    integrated into the vanilla Linux kernel with the 2.6.33 release. 
    refers to block devices designed as a building block to form high availability (HA) clusters. This is done by 
    mirroring a whole block device via an assigned network. DRBD can be understood as network based raid-1. 

====== Linux version and Release ======

    uname -a
    /etc/issue

====== Opensuse Firewall Configuration ======

Trusted Network

From: http://forums.opensuse.org/english/get-technical-help-here/applications/414092-iptables-allow-certains-ips-block-everyone-else.html

    You can set that in Yast --> System -> /etc/sysconfig editor --> network --> firewall 
    --> susefirewall2 --> FW_TRUSTED_NETS
    
    like so: FW_TRUSTED_NETS="192.168.1.0/24 10.0.0.99" would allow all 
    of the 192.168.1.x series plus the individual IP 10.0.0.99.

====== Linux Time Conversion ======

http://www.epochconverter.com/

    Timestamp in milliseconds: 1365448421000
    Human time (your time zone): Monday, April 08, 2013 3:13:41 PM
    Human time (GMT): Mon, 08 Apr 2013 19:13:41 GMT

    Timestamp in milliseconds: 1365426815000
    Human time (your time zone): Monday, April 08, 2013 9:13:35 AM
    Human time (GMT): Mon, 08 Apr 2013 13:13:35 GMT

    Timestamp in milliseconds: 1364598852000
    Human time (your time zone): Friday, March 29, 2013 7:14:12 PM
    Human time (GMT): Fri, 29 Mar 2013 23:14:12 GMT

    Timestamp in milliseconds: 1364577144000
    Human time (your time zone): Friday, March 29, 2013 1:12:24 PM
    Human time (GMT): Fri, 29 Mar 2013 17:12:24 GMT

    Timestamp in milliseconds: 1363978800000
    Human time (your time zone): Friday, March 22, 2013 3:00:00 PM
    Human time (GMT): Fri, 22 Mar 2013 19:00:00 GMT


    Timestamp in milliseconds: 1364014800000
    Human time (your time zone): Saturday, March 23, 2013 1:00:00 AM
    Human time (GMT): Sat, 23 Mar 2013 05:00:00 GMT


    Timestamp in milliseconds: 1364081400000
    Human time (your time zone): Saturday, March 23, 2013 7:30:00 PM
    Human time (GMT): Sat, 23 Mar 2013 23:30:00 GMT

    Timestamp in milliseconds: 1364117400000
    Human time (your time zone): Sunday, March 24, 2013 5:30:00 AM
    Human time (GMT): Sun, 24 Mar 2013 09:30:00 GMT
    
====== Cron Messages ======

Suse 10.x in %%/var/log/messages%%

====== Cron ======

<code>
#|   hour (0-23)
#|   |    day of the month (1-31)
#|   |    |   month of the year (1-12 or Jan-Dec)
#|   |    |   |   day of the week (0-6 with 0=Sun or Sun-Sat)
#|   |    |   |   |   user
#|   |    |   |   |   |   commands
#|   |    |   |   |   |   |
# Each line has five time-and-date fields
# followed by a username (if this is the system crontab file),
# and followed by a command.
# 20   1    1   *   *  smolt /usr/bin/smoltSendProfile -c > /dev/null 2>&1
# top of every other hour :0  
0   */2   *    *   *    root /root/Desktop/own-p  > /var/log/own-p.log 2>&1
</code>



====== BAD FILE MODE ======


From: http://www.cyberciti.biz/faq/unix-linux-cron-bad-file-mode-error/

<code>
    All you have to do it set 0644 (rw-r--r) permission i.e. remove world writable 
    file permissions 
    
From: http://old-en.opensuse.org/Packaging/SUSE_Package_Conventions/Cron_Jobs

    As defined in /etc/crontab, cron executes the script /usr/lib/cron/run-crons 
    every 15 minutes. It looks for scripts in the directories /etc/cron.{hourly,
    daily,weekly,monthly} and checks which should be executed. The information about 
    last run is stored in files below /var/spool/cron/lastrun.
</code>