See you there 🙂
Today I read about the problem with one assertion in systemd, I read it in the amazing blog of Andrew Ayer (Click here), Right now is necessary document this problem using the Proof of Concept published in the systemd github page.
For documentation purposes I use screenshots but the final report for the systemd bug tracking is in plain text :).
- Host OS: Fedora 24 Desktop (only official Fedora desktop rpmfusion repos) updated (9/29/2016). https://paste.fedoraproject.org/438231/16649614/
- systemd: 229
- Hardware: Lenovo thinkpad T440s.
The calls to systemd based commands (systemd-nspaw, systemctl, etc) hangs and later shows a timeout message. No general system degradation.
Ok, Andrew Ayer has a very clever point but my opinion is better help to debugging and improve systemd.
Note: For Fedora 25 see this post http://www.bt0.ninja/packettracer-7-0-in-fedora-25/
Note: For Fedora 26 see this post http://www.bt0.ninja/packettracer-7-in-fedora-26
Note: For Fedora 27 see this post http://www.bt0.ninja/cisco-packettracer-7-1-on-fedora-27
Cisco Packet Tracer 7.0 is created by Cisco SystemsTM and is now provided for free distribution. Self learners are now able to download Cisco Packet Tracer after registering on Cisco Netacad website. A free Packet Tracer 101 (English), a 1-hour self-paced online course is also offered to every registered (free) student to help them get started with Pracer 7.0, So you can register and download from here.
The cisco packettracer 7.0 is available for GNU/Linux under the next requirements:
- nss and ssl libraries.
- QT4 script-tools, WebKit and QT3 backward support.
- Cisco NetSpace account. (Mandatory)
We need install some libraries as follows:
$ sudo dnf install zlib-devel ncurses-devel gtk2 glibc glibc-devel \\ libstdc++ libX11-devel libXrender libXrandr libusb libXtst nss \\ qt qtwebkit
This time we have x86 (32bits) and x86_64(64bits) Packet Tracer packages, to be sure what is our version, run:
$ uname -m
Still we have the ugly openssl-1.0.0 dependency, so if we have a i686 (32bits) version of Fedora 24:
$ wget http://www.deltaeridani.com/openssl-lib-compat-1.0.0i-1.fc24.i686.rpm $ sudo rpm -Uvh openssl-lib-compat-1.0.0i-1.fc24.i686.rpm
Today most people have a x86_64 machine and this time we have two options for resolve the OpenSSL dependency:
1.- Just download the package generated by me and simply trust me (I call this the ugliest method because i don’t provide any warranty):
$ wget http://bt0.ninja/rpm/openssl-lib-compat-1.0.0i-1.fc24.x86_64.rpm $ sudo rpm -Uvh openssl-lib-compat-1.0.0i-1.fc24.x86_64.rpm
2.- Compile your own version (I call the “just ugly” method because you can check the source):
First get the code:
$ wget http://archives.fedoraproject.org/pub/archive/fedora/linux/releases/17/Everything/source/SRPMS/o/openssl-1.0.0i-1.fc17.src.rpm $ sudo dnf install @development-tools fedora-packager krb5-devel $ sudo rpm -Uvh openssl-1.0.0i-1.fc17.src.rpm
For the build process we need super user access:
$ su - # cd rpmbuild/SPECS/ # wget http://bt0.ninja/rpm/openssl-lib-compat-1.0.0.spec # rpmbuild -bb openssl-lib-compat-1.0.0.spec # rpm -i ../RPMS/x86_64/openssl-lib-compat-1.0.0i-1.fc24.x86_64.rpm # exit
So many thanks to Yves L’ECUYER owner of http://www.deltaeridani.com, the original spec and the example are all from him.
Cisco Packet Tracer 7.0 will be downloaded from Cisco Networking Academy Portal,
$ tar -xzf PacketTracer70_linux.tar.gz && cd PacketTracer70 $ chmod +x install $ sudo ./install
After accept the EULA, the installation begins, we need set the environment variables with the next command:
$ sudo /opt/pt/set_ptenv.sh
Graphical Launcher on Gnome
At this point packettracer is ready to use but another useful thing to do is create a desktop Cisco Packet Tracer icon to launch it, first download the icon:
$ wget http://upload.wikimedia.org/wikipedia/en/d/dc/Cisco_Packet_Tracer_Icon.png $ sudo mv Cisco_Packet_Tracer_Icon.png /usr/share/icons/
With our favorite plain text editor we will create the file
/usr/share/applications/packettracer.desktop as follows:
[Desktop Entry] Encoding=UTF-8Name= PacketTracer 7.0 Comment=Networking Cisco GenericName=Cisco PacketTracer 7 Type=Application Exec=/opt/pt/packettracer Icon=/usr/share/icons/Cisco_Packet_Tracer_Icon.png Categories=Education; StartupNotify=true
Now we will run Cisco Packet Tracer 7.0 from our Desktop:
systemd is a system and service manager for Linux.It is (retro) compatible with systemV and LSB init scripts. It is relatively new but has been widely accepted by major Linux distributions.
Frankly, at first, I did not like it, I saw it too complex, bulky and don’t see any shell script on the service management, but remembering the wisdom of Master Foo Discourses on the Two Paths, i give it one opportunity and I just fell in love.
I’ll outline a few things that I find awesome about systemd, In no particular order:
1.- It don’t use Shell scripts
Ok it is not clear but systemd is faster and scale better in bootup, when we use scripts they call many times commands like grep, awk, cd, ls and others, so this execution is slow (but easy to hack).
2.-Use the units concept
One unit is a file than encodes information about a service (.service),a mount point (.mount),a device(.device), a socket (.socket), a timer (.timer) and other abstract entities, we can enable, disable, start, stop , restart, mask units. See
man systemd.unit for details.
$ sudo systemctl start unit $ sudo systemctl stop unit $ sudo systemctl enable unit $ sudo systemctl disable unit
3.- We can check the system state
Just with this commands:
$ systemctl status
and list running and failed units
$ systemctl list-units $ systemctl --failed
4.- It is hotplug capable
systemd assumes that all resources may appear and dissapear at any time, this is one of the reasons because systemd depends of dbus but right now, our systems become dynamic systems with lowest downtime when adding or removing hardware.
5.- It is modular
All of what is now rc.sysinit is split out into many independent services, each of which is well documented and easy to understand.
6.- Can deploy containers with systemd-nspawn
I talk about it in this post.
7.- The systemd timers
Timers have built-in support for calendar time events, monotonic time events, and can be run asynchronously.Timers Timers can be used as an alternative to CRON and “at command” but timers have a more complex syntax than crontab entries but our duty as sysadmins is learn it.
8.- systemd is a cross-distro project
Every major and many, many minor distros have had people contributing to systemd, it is the default in Debian 8, Fedora, OpenSuse, Ubuntu (Leaving Upstart for systemd) and many many others distros use systemd.
9.- systemd do power management
You can poweroff, restart, suspend or hibernate using systemd. (for unprivileged users you need polkit)
$ sudo systemctl poweroff $ sudo systemctl reboot $ sudo systemctl suspend $ sudo systemctl hibernate
10.- Have a build-in logging system
systemd has its own logging system called the journal; therefore, running a
syslog daemon is no longer required. To read the log, use:
The systemd journal event notification message logging classification corresponds to classical BSD syslog protocol style (RFC 5424).
For more information about systemd:
- PID ONE, Lennard’blog
- systemd man pages
With the System Administrator Appreciation Day soon and my heart broken because the people say:
“The SysAdmin day is so cool but we haven’t one SysAdmin, right?”
“We don’t have problems with Voip/Servers/Computer stuff, this thinks never fail”
“Don’t go to the Site!!! Something lives there and is Deadly (and/or too sexy)
The people do this comments and others with you are a good SysAdmin or in my case people can’t see me cause i’m a ninja. So here are some bits of system administration:
Performing backups is perhaps the most important job of the SysAdmin, Backups are boring and time consuming but absolutely necessary so we have a lot of tools like:
- rsync, git-annex or the powerful taskd for file synchronization.
- duplicity, btar, dar and the legendary dump for incremental backups (chunk and file incremental).
- Bacula, BackupPC and burp for Network, distributed and hardcore backups (i love bacula).
Although this tools can automate the backup process, still is the sysadmin’s job to make sure that backups are executed correctly and on schedule.
Maintaining systems documentation:
Commonly a system is changed in order to fit organization’s needs, so our job is track and document the changes from the vanilla-plain version of the system, also backup and guard this documentation is our job, keep update this documentation can be the difference in a critical time (by example: when we need request support). This is a small (and incomplete) list of important documentation:
- Hardware documentation (warranty, support phones, owner’s manual, physical location, etc)
- Software documentation (warranty, support phones, owner’s manual, local change logs, etc)
- Network (equipment, scripts, cabling, configurations, etc)
- Record of backup status (files, software, databases, etc)
- Local procedures and policies.
Installing and upgrade software
This is one of those things for which we need to have cold blood, Every software, every patch, every update should be staged for testing before being deployed.
So many times we receive news above vulnerabilities, critical upgrades or simple bugfixes for our software versions but never upgrade or patch software in production system before test it, no matter how critical is this upgrade patch, It has more value for organizations running a vulnerable system than one aren’t working, it is a calculated risk. (exception: the system is already down and this upgrade solve the problem)
As patches and security updates are released they must be incorporated smoothly in the production systems.
When apply upgrades or patches always do:
- Out of production hours.
- Have a rollback plan in case of failure
- Document day, hour, person in charge, and reason of the upgrade.
The process of adding and remove users can be automated, but certain administrative decisions must still be made before a user can be added or removed, by example:
- Follow the principle of least privilege when adding new accounts.
- Backup files from users before deleting their accounts.
- On vacations disable user’s account.
- Be patient with the “Forgotten passwords”
Adding and removing hardware
From the simple task of add a printer to the complex job of adding a disk array, the hardware support is a very important activity of the system administrator. like a software updates we always need very careful and have a rollback plan. it is vast and complex topic, so I’m only give you one advice about it:
Always be aware of end-of-life of your hardware (the time when the provider stop maintain and produce parts for your hardware), before you need planning about get some parts or (better) update the hardware.
if you did not prepare, pray is a good option.
Monitoring the system
I have two favorite protocols “Internet Protocol Control Protocol” and “Simple Network Management Protocol”, the first because every time i say it the people laughs, the second because It makes my life easier, from the single cacty to the mosnters Nagios and OpenNMS, we can track many indicators such:
- Network traffic.
- CPU Load
- Disk usage
- many others.
Now more than ever, we have an arsenal of tools to check our system status, an example that I love is systemd because:
- Is the default init system for the major distributions of GNU/Linux.
- Can show the general services status of the system :
- Can generate containers with systemd-nspaw.
- Can schedule jobs with systemd-timers. (A cron alternative)
for one really good explanations of why use systemd check the Lennart’s blog (one of the creators of systemd).
Another very good tool is use
dmidecode command to get information about the hardware status, useful if your servers are in Far Far Away kingdom and you can’t physically check hardware alarms (you know, the scariest blinding leds).
Vigilantly monitoring security
In these dark times always do routine checkups:
- Check password strength with John the Ripper
- Check open ports with nmap
- Review any changes on config files (You can create a git repository on the /etc directory you can check changes and backup then at the same time).
- Implement a IDS or IPS (Coff Coff Nagios is open source great idea)
- Subscribe to SysAdmin and Security Newsletters like SANS,LWN, securityfocus, etc.
- Check the industry best practices and adopt those that meet the requirements of your organization.
The security is one complex and holistic thing but all SysAdmin must know the basics.
Four general tips more
- I talk a lot about planning, beside of the IT certifications, if you have knowledge about project management not only you will boost your career, you will be best SysAdmin, consider a PMI certification.
- Adopt and contribute to one open source project, if you use a open source tool daily you can suggest and do improvements, remember nobody knows a software piece more than their developers. (suggestions: systemd, drill, ovirt,docker,etc).
- Master containers (Docker, sistemd-nspawn), in few years this knowledge will be indispensable.
- Embrace DevOps, today’s organizations are seeking talent who can design, develop and deploy software for production environment. We are (the SysAdmins) the best options, how many python/perl/bash scripts we wrote and test in our daily job? We are good programmers than also known how to deploy and maintain this software up and running.
Happy System Administrator Appreciation Day !!!