Zebex Z-3151HS bar code reader - Windows 10 - Unknown USB, USB device not recognized
Thursday, July 11. 2019
Among the number of toys I have, are couple of Zebex bar code readers. Since forever (or 2013), I've had issues with Windows not detecting the newly attached USB-device correctly. See my previous article Windows 7 unable to detect a HID barcode scanner for details. That was on a Zebex Z-3000 to be exact.
During all these years, the problem has not solved itself and all my attempts to fix have been not-so-successful. The reader I've been most recently used is an improved one using a laser to read the data, a Z-3151HS (the HS stands for High Speed). The version query will return a single-line string containing following:
Model Z3151HS S01.01
Ver
01.27
Date
01-18-2019
On a plugin, the USB human-interface-device (or HID, or keyboard) does this:
Nobody loves seeing an USB device not recognized -popup, or Device Descriptor Request Failed on device manager. That's a sign of a major malfunction.
Luckily, in this case without spending too much time, little bit of troubleshooting became fruitful and both problem reason and a fix were found. The bar code reader loves being in a wrong mode. This is an USB-device, but no matter what I try, on plugin the device will be in IBM PC/AT/PS/2 Keyboard emulation mode. That incorrect mode makes the newly plugged in USB-device not respond to a Windows intiated device query. As you might think, your Windows will be pissed about the failure and bark about it. Obviously, the device should be in USB-mode to handshake properly with Windows, that's a no-brainer.
Again, the mode can be changed easily by scanning some bar codes (these are actually in the manual too):
Enter configuration mode, switch to USB-mode and end configuration mode. Poof! Now Windows 10 sees the HID USB-thingie ok and it does work correctly. The obvious problem is, that you really do need to do it EVERY SINGLE TIME you plugin the device to your computer. Not cool! Numerous attempts to fix the mode-select have failed. If you have a suggestion, I'd be happy to try it.
Bonus: Firmware upgrade
My unit had a measly 1.03 firmware when I bought it. Obviously, I've been upgrading firmwares while hoping the problem would be solved somehow. No such joy yet.
New firmwares can be downloaded from Zebex website @ https://www.zebex.com/en/product/index/20/Z-3151HS with appropriate tooling to do the update. Since this is on a computer, nothing will ever work as smoothly as you'd like. On an attempt to run the firmware upgrade tool, this will happen:
In front of your eyes, a failure will occur and a message will state: Make sure the device work under USB-Boot mode. I'm not sure whose English grammar is better, mine or that person who wrote that sentence, but the problem stands. You need to get your device into USB-Boot -mode and you have zero clue on how to do that.
Tons of googling, reading forum posts and manuals will reveal, that such a sequence does exist. You need to scan following bar codes:
Yet again, go for configuration mode, and place the device into USB update -mode. After that, your firmware update will proceed to actual update.
I'll hope these tips will help some poor user trying to get his/hers reader working.
Enjoy scanning!
systemd setting overrides
Monday, June 17. 2019
In couple past posts of mine, I've instructed people to do alter systemd service descriptions. Examples from Randomness in computers and Handling /run with systemd. As we all know, systemd is quite a beast. It just keeps on giving complexity as we stumble along trying to grasp all of it.
For example:
To add more command arguments to rngd.service, you can do what I instructed earlier. You can copy /usr/lib/systemd/system/rngd.service to /etc/systemd/system/, edit the file and do a systemctl daemon-reload to update the changes.
If you want to choose more systemd'ic (Python developers always say "pythonic") way, you can do a:
systemctl edit rngd
This command will open a text-editor. The editor is your default one from EDITOR environment variable, or if you haven't picked one, a default will be chosen for you by your favorite Linux distro vendor.
What you should make the text file contain, is following three (3) lines:
[Service]
ExecStart=
ExecStart=/sbin/rngd -f --rng-device=/dev/TrueRNG --fill-watermark=4000
Those lines will re-define service description. First by clearing out the previous value(s) and then defining a new one. On save, this setting will take automatically effect and you don't have to do anything else. Also, this setting is persisted in a file called /etc/systemd/system/rngd.service.d/override.conf. Of course, you can create that particular file yourself, but then the familiar systemctl daemon-reload is needed to make your changes stick.
Nice and easy! 
Adding a source of randomness to a Linux
Monday, June 3. 2019
Randomness in computers
You don't need to know much about computers to understand, that computers cannot do random things. Yes, all programming languages and libraries do offer you a rand()-function to emulate randomness. However, the resulting output will follow the carefully crafted programming implementing this "randomness". The most trivial pseudo-random functions will merely provide a sequence of numbers appearing random, but this sequence can be reset to start from beginning making the "randomness" predicatable. That's not really very random, huh!
Improved randomness in computers
To be fair, there does exist improved pseudo-random algorithms which take their initial seed-values from something volatile (time is one such volatile parameter) making the quality of randomness better. Still, even high-quality pseudo-random algorithm is just complex sequence of operations, which will produce duplicate results on same input values. Sometimes its just very tricky to craft a situation where all of the input values would match.
If somebody is capable of doing that, your randomness changes into predictability. Read the story of Dual_EC_DRBG on Wikipedia https://en.wikipedia.org/wiki/Dual_EC_DRBG. When you're generating your precious private keys, you don't want anybody (including NSA) to be able to guess what you have there.
Random source in Linux
Since a proper random source is something every single user, developer and sysadmin would love to have, the problem has been approached on your Linux by authors of the operating system. An excellent description can be found from Wikipedia article https://en.wikipedia.org/wiki//dev/random#Linux. Briefly put, your Linux will collect environmental entropy from number of sources (including human interaction with keyboard and mouse) to a pool, which can then be used to produce naturally random numbers. It actually works very well, the quality of randomness is top-notch.
Obvious problem with this approach is, that you cannot pull too many random numbers out of this source without exhausting it. The fix is to keep typing something while moving your mouse (not a joke!) to generate entropy for the random source. This will eventually help fill the entropy pool and /dev/random will spit couple bytes more.
Those users who have exhausted their /dev/random on an idling rack server without a console keyboard, mouse and video know that it takes painfully long for the entropy pool to fill. A busy server doing something will be able to fill the pool much faster.
A real random source
If you need a real proper random source, which works without human intervention and can provide really good randomness as a stream, there are possibilities on hardware. I know of two good ones, Simtec Electronics Entropy Key and ubld.it TrueRNG Hardware Random Number Generator.
Note: if you consider getting one, get the TrueRNG version 3 (http://ubld.it/truerng_v3). Its just that I have the 1st gen version at hand and haven't found the reason to upgrade.
My TrueRNG looks like this:
It is essentially an USB-stick.
Linux lsusb info essentially identifies it as a Microchip (vendor ID 0x04d8) manufactured USB-device (with ID 0xf5fe) providing RS-232 communications:
Bus 002 Device 009: ID 04d8:f5fe Microchip Technology, Inc.
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 2 Communications
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 8
idVendor 0x04d8 Microchip Technology, Inc.
idProduct 0xf5fe
bcdDevice 1.00
iManufacturer 1 ubld.it
iProduct 2 TrueRNG
iSerial 0
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 0x0043
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 0
bmAttributes 0x80
(Bus Powered)
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 2 Communications
bInterfaceSubClass 2 Abstract (modem)
bInterfaceProtocol 1 AT-commands (v.25ter)
iInterface 0
CDC Header:
bcdCDC 1.10
CDC ACM:
bmCapabilities 0x02
line coding and serial state
CDC Union:
bMasterInterface 0
bSlaveInterface 1
CDC Call Management:
bmCapabilities 0x00
bDataInterface 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x81 EP 1 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x000a 1x 10 bytes
bInterval 1
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 10 CDC Data
bInterfaceSubClass 0
bInterfaceProtocol 0
iInterface 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x02 EP 2 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Device Status: 0x0001
Self Powered
And by looking at /dev/, there is a /dev/ttyACM0. That's how udevd will populate a CDC-device when it sees one.
How is this a "true" random source?
Oh, that's easy. The device will produce a random 0 or 1 bit constantly when its on. Or to be precise, there is an internal algorithm producing those based on a constant flow of electrons on a transistor PN-surface. The exact phenomenon is called avalance effect or avalance breakdown. For those who can do electronics, there is a good explanation about this in Difference Between Avalanche Breakdown and Zener Breakdown (I borrowed the visualisation pic from above link).
To (over)simplify that, in a carefully constructed electronic circuit, inside a transistor an electron may or may not be emitted on the other side of a semiconducting surface. The occurrence is as random as it can be in nature. Other circuitry will detect this random flow of electrons (or lack of flow) to produce ones and zeros.
What makes this a really good for randomness, as it is well established that this avalance of electrons will happen. Also, it will happen often enough to produce a stream of events. It's just that we don't know exactly WHEN the avalance of electrons will happen. If you time-slice this to slots, a slot can be empty (no avalance) or full (electrons avalanching).
Linux tweaking:
udev
Anybody having multiple devices in their Linuxes knows, that you really cannot control which device name some specific device will get on reboot. To overcome that, udevd can be instructed to do things when it sees a device. My rules for TrueRNG include setting it to highest possible speed and creating a symlink-device so, that I can point to a known source of random. Also, I'm loosening access to that source of randomness to any users belonging to dialout-group. If I wouldn't do that, only root would have access to this fine random-source.
My /etc/udev/rules.d/99-TrueRNG.rules contains:
SUBSYSTEM=="tty", ATTRS{product}=="TrueRNG", SYMLINK+="TrueRNG", RUN+="/bin/stty raw -echo -ixoff -F /dev/%k speed 3000000"
ATTRS{idVendor}=="04d8", ATTRS{idProduct}=="f5fe", ENV{ID_MM_DEVICE_IGNORE}="1", GROUP="dialout", MODE="0664"
If you want to take your random-device for a spin, you can do something like:
dd if=/dev/TrueRNG of=random.bytes bs=64 count=1024
That would create a file of 64 KiB containing very very random bytes. In theory you can just cp data out of the character device, but since it has an infite flow, you'll need to cut it at one point.
rngd
Remember the part I said earlier about Linux using your keypresses and mouse movements as entropy source for randomness. Even with the USB-stick popped into a PC, that still remains the case. What needs to be done next is to offer a helping hand to the Linux kernel and make sure the entropy pool is always full.
My Fedora has package called rng-tools. It is packaged from Mr. Horman's https://github.com/nhorman/rng-tools. What's in there are the tools for pumping those precious truly random bits out of the USB-source to Linux kernel's entropy pool. As default, rngd will use /dev/hwrng as the source for randomness. Some Linuxes don't have that device at all, some Linuxes point that into CPU's random source. What's guaranteed, it will not point to your USB-stick! We need to change that.
Btw. you might be horrified by the fact, that something is fidding with your randomness. The exact bits transferred from USB to entropy pool won't be the actual bits getting out of /dev/random. Your keypresses and many other events are still a factor. Its still a good idea to not run randomness-monitoring malware or spyware in your Linux.
Systemd works so, that I did create a copy of /usr/lib/systemd/system/rngd.service into /etc/systemd/system/rngd.service. The contents of the copy in /etc/systemd/system/ can be freely modified and it has priority over the /usr/lib/systemd/system/ one. The only change I made was to have the ExecStart-line say as:
ExecStart=/sbin/rngd -f --rng-device=/dev/TrueRNG --fill-watermark=4000
When rngd-service would be started, it will use the USB-stick as source and make sure, there are at least 4000 bits of entropy in the pool.
Making sure rngd setup works
At any given point, you can query how many bits are available in the Linux entropy-pool:
cat /proc/sys/kernel/random/entropy_avail
Since my setup is working correctly, it will display a number greater than 4000 and smaller than 4096. The upper limit comes from /proc/sys/kernel/random/poolsize, which is a hard-coded number from Linux kernel source.
Hint: If you do the stupid thing like I did and set the /proc/sys/kernel/random/write_wakeup_threshold (using --fill-watermark) into 4096 (or above), your rngd will keep hogging CPU like there is no tomorrow. It is impossible for the pool to contain maximum number of bits at any given time. Give your system a break and set the threshold bit lower than max.
Finally
It's always nice to know for a fact, that random numbers are random. This fact can be verified and has been verified by number of other people.
Enjoy!
Bacula 9 vchanger: Tape count fix
Sunday, June 2. 2019
One of the first ever blog posts I've written here is about Bacula, the open-source backup software (more at https://www.bacula.org/). I published Fedora 17 binaries for the virtual tape changer running for Bacula 7. The post from year 2013 is here.
Running Bacula in Fedora Linux isn't much of a trick, ready-made binaries are available by the distro and configuring one is covered in Bacula's documentation. Then again, running Bacula with a NAS (see Wikipedia for Network-attached storage) as storage backend is where things get very very tricky. I've written about my Qnap NAS-device's support earlier, see the post about that.
Since its inception, Bacula is baked to require a tape drive (or drives) and a set of tapes (a single tape is supported also). Given modern day computing environment, actual physical tapes aren't used that much. Even I stopped using DLT (Wikipedia Digital Linear Tape) or LTO (Wikipedia Linear Tape-Open) tapes years ago and went for an easy, fast and inexpensive solution for storing my backups on a NAS. So, I really do need to have a concept of a "tape" somehow. That's where the virtual Bacula tape changer steps in. It is a piece of software attaching to Bacula autochanger API emulating a virtual "tape" drive and set of tapes with all the necessary operations, but doing all that on a filesystem. More details about autochangers can be found from Bacula Autochanger Resource page.
The obvious idea is to create a set of files to act as a set of "tapes". For system administration purposes, the tapes are just files in a subdirectory. Smart thing to do is to make that particular subdirectory located on a NAS to store the backups where there is plenty of external capacity outside your system. In my case, I'll access them over an iSCSI-mounted filesystem. More details about iSCSI on a Linux can be found from RedHat Enterprise Linux 7 manual pages at https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/storage_administration_guide/online-storage-management#osm-target-setup. For those planning something similar: I chose NOT to go with a NFS. A NFS-connection get stuck very easily and you will be rebooting your stuff a lot. See How-To: Release Stuck NFS Mounts without a Reboot @ Linux Journal for more about that.
When I went to Fedora 29, my Bacula setup got an automatic bump to version 9. My previous setup was for Bacula version 7 and quite soon I realized that I needed to alter my vchanger somehow to get it to support version 9. Bacula-guys did make changes to autochanger-API in their version-bump process. Luckily vchanger author was ahead of me and I got the code from http://sourceforge.net/projects/vchanger/. Soon realized that when I did a simple command of vchanger /etc/qnap.conf LIST, it displayed an extra tape which didn't exist in reality. I was puzzled. Old setup displayed the tape count correctly.
I did some C++ debugging and found out an obvious bug in the code. In src/diskchanger.cpp, DiskChanger-class InitializeVirtSlots()-method calculates the last changer slot numer incorrectly. It is guaranteed to be one-off. After fixing this, I contacted the vchanger author Mr. J. Fisher about my findings, and he agreed, there was a bug in his code.
Unfortunately, couple of months have passed and there is no 1.0.3 release yet, so the fix isn't in the SourceForge git-repo yet. For Fedora-users, my RPMs are available at http://opensource.hqcodeshop.com/Bacula/vchanger for B9/. Go get them there! I've been using those since last December, so I think my fix is correct and doesn't introduce any issues.
StackExchange flair received
Monday, March 11. 2019
Whoa! I finally hit the long awaited 200 point mark in Stack Overflow. The good part about that is, Stack Exchange starts publishing a public badge they'll call "flair". They do this to make it possible for me to publicly boast about my prowess. To get some public boasting going on, my flair looks like this:
All of you Peeping Toms out there, I'll save you couple keystrokes of googling: My 
public user profile is at https://stackexchange.com/users/1684769/hqjatu
Fedora dhclient broken
Monday, December 10. 2018
Windows 10 with Microsoft's OpenSSH
Sunday, December 2. 2018
Without thinking it too much, I just went for a SSH-connection on a Windows 10 box with the way it's typically done:
ssh -i .ssh/id_nistp521 user@linux-box
When the result was not a private key passphrase question, but a: Bad owner or permissions on .ssh/config, I started thinking about it. What! What? Why! It worked earlier, why won't it anymore?
For the record:
I am an avid Cygwin user. So, I get a very very Linuxish experience also on my Windows-boxes. So, don't be confused with the rest of the story. This is on a Windows 10, even if it doesn't appear to be so.
Back to the failure. I started poking around the permissions. SSH-clients are picky on private key permissions (also config file), so I thought that something was going on. Doing a ls -l:
-rw------- 1 jari None 547 Nov 12 17:25 config
-rw------- 1 jari None 444 Jul 15 2017 id_nistp521
Nope. Nothing wrong with that. Still, something HAD to be wrong, as this wasn't acceptable for the client. Doing a which ssh gave it away. I was expecting to see /usr/bin/ssh, not /cygdrive/c/Windows/System32/OpenSSH/ssh!!
So, who put an OpenSSH client to my Windows-directory? Why? When? What kind of sorcery is that? Environment variables:
Yes, there is a PATH-entry for OpenSSH before Cygwin. In the directory, there is a full set of OpenSSH-tools:
Version is 7.6:
OpenSSH_for_Windows_7.6p1, LibreSSL 2.6.4
The expected version in Cygwin is 7.9:
OpenSSH_7.9p1, OpenSSL 1.0.2p 14 Aug 2018
So, to fix this, I yanked the PATH-entry away. Now my SSH-connections worked as expected.
Little bit of googling around landed me on an article OpenSSH in Windows 10! in MSDN blogs. This is on January 2018 and apparently this stuff landed on my Windows in April update (build 1803). Also in article What’s new for the Command Line in Windows 10 version 1803, I found out that also tar and curl were added.
Ultimately this is a good thing. Now that I know this stuff is there as default, there is no need to go load a PuTTY or something for a random SSH-thing you just want to get fixed on a remote box.
PS4 controller in a PC
Wednesday, November 14. 2018
Lately, I've been playing Mudrunner: Spintires a lot. That's a really weird game about logging machinery and mud. For some strange reason I find hauling logs from a lake through mud really entertaining. Why logs are located a "lake" is beyond me.
During the gameplay, player needs to operate number of different heavy machinery. This involves driving a skidder, a heavy truck or operating a crane to get the logs loaded. I tried doing that with a traditional mouse and keyboard config. I kinda managed to do it, but anybody who has driven a real car or truck or flown an airplane using only a keyboard knows, it's very tricky. Then I got a hint, that a Playstation 4 controller is really good with that game.
A-haa! All I need to do is hook up my PS4-controller into my PC using ... well... dunno. As Google search engine is a good friend, I found a project DS4Windows from Github https://github.com/Ryochan7/DS4Windows. It will convert a PS4-controller into an Xbox controller, which will work perfectly with most games.
Just hokk up an USB-cable to the controller, run the software, and:
You're done! It really is that simple. Now spinning tires in mud is much much more enjoyable!
Arch Linux failing to start network interface, part 2
Saturday, March 17. 2018
I genuinely love my Arch Linux. It is a constant source of mischief. In a positive sense. There is always something changing making the entire setup explode. The joy I get, is when I need to get the pieces back together.
In the Wikipedia article of Arch Linux, there is a phrase:
... and expects the user to be willing to make some effort to understand the system's operation
The is precisely what I use my Arch Linux for. I want the practical experience and understanding on the system. And given it's rolling release approaches, it explodes plenty.
Back in 2014, Arch Linux impemented Consistent Network Device Naming. At that time the regular network interface names changed. For example my eth0 become ens3. My transition was not smooth. See my blog post about that.
Now it happened again! Whaat?
Symptoms:
- Failure to access the Linux-box via SSH
- Boot taking very long time
- Error message about service
sys-subsystem-net-devices-ens3.devicefailing on startup
Failure:
Like previous time, the fix is about DHCP-client failing.
You vanilla query for DHCP-client status:
systemctl status dhcpcd@*
... resulted as nothingness. A more specific query for the failing interface:
systemctl status dhcpcd@ens3
... results:
* dhcpcd@ens3.service - dhcpcd on ens3
Loaded: loaded (/usr/lib/systemd/system/dhcpcd@.service; enabled; vendor pre>
Active: inactive (dead)
Yup. DHCP failure. Like previously, running ip addr show revealed the network interface name change:
2: enp0s3: mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 52:54:52:54:52:54 brd ff:ff:ff:ff:ff:ff
There is no more ens3, it is enp0s3 now. Ok.
Fix:
A simple disable for the non-existent interface's DHCP, and enable for the new one:
systemctl disable dhcpcd@ens3
systemctl enable dhcpcd@enp0s3
To test that, I rebooted the box. Yup. Working again!
Optional fix 2, for the syslog:
Debugging this wasn't as easy as I expected. dmesg had nothing on DHCP-clients and there was no kernel messages log at all! Whoa! Who ate that? I know, that default installation of Arch does not have syslog. I did have it running (I think) and now it was gone. Weird.
Documentation is at https://wiki.archlinux.org/index.php/Syslog-ng, but I simply did a:
pacman -S syslog-ng
systemctl enable syslog-ng@default
systemctl start syslog-ng@default
... and a 2nd reboot to confim, that the syslog existed and contained boot information. Done again!
What:
The subject of Consistent Network Device Naming is described in more detail here: https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/networking_guide/ch-consistent_network_device_naming
Apparently, there are five different approaches on how to actually implement the CNDN. And given the old ens-device, which is according to PCI hotplug slot (enS for slot) index number (Scheme 2), the new naming scheme was chosen to be physical location (enP for physical) of the connector (Scheme 3).
The information of when/what/why the naming scheme change was made eludes me. I tried searching Arch discussion forums at https://bbs.archlinux.org/, but nothing there that I could find. But anyway, I got the pieces back together. Again!
Update 30th March 2018:
Yup. The interface naming rolled back. Now ens3 is the interface used again. Darnnation this naming flapping!
Destiny 2 Nightingale error [Solved!]
Thursday, February 22. 2018
As an employee of (a subsidiary of) Activision/Blizzard, last year those who wanted, got keys for Destiny 2.
It never worked! I never go to play it. 
On game launch:
... and BANG! The dreaded Nightingale error:
For past couple of months, that's how much I saw Destiny 2. That isn't much. Darn!
Actually, there is an Internet full of people having the same problem. There are various solutions to, which have worked for some people and for some, not so much.
After doing all the possible things, including throwing dried chicken bones to a magical sand circle, I ran out of options. I had to escalate the problem to Blizzard Support. Since this wasn't a paid game, obviously it didn't reach their highest priority queue. But ultimately the cogs of bureaucracy aligned and I got the required attention to my problem. But ... it was unsovalvable. Or it seemed to be one.
Today, after escalating the problem back to Bungie, they pointed out the problem. My computer didn't manage to reach their CDN, so the game got angry and spat the Nightingale on my face. They also hinted me about what my computer did instead and ...
Somewhere in the guts of the Destiny 2, there is a component reading the value of environment variable HTTP_PROXY. I had that set on the PC because of ... something I did for software development years ago.
After deleting the variable, the game started. WHOA!
So, it wasn't my router, DNS, firewall, or ... whatever I attempted before. Problem solved!
Arch Linux failing to update man-db
Friday, January 26. 2018
This week seems to be especially hard on my Linuxes. Doing a regular pacman -Syu started spitting crap on me:
error: failed to commit transaction (conflicting files)
man-db: /usr/bin/accessdb exists in filesystem
man-db: /usr/bin/apropos exists in filesystem
man-db: /usr/bin/catman exists in filesystem
man-db: /usr/bin/convert-mans exists in filesystem
man-db: /usr/bin/lexgrog exists in filesystem
man-db: /usr/bin/man exists in filesystem
man-db: /usr/bin/mandb exists in filesystem
man-db: /usr/bin/manpath exists in filesystem
man-db: /usr/bin/whatis exists in filesystem
man-db: /usr/lib/man-db/globbing exists in filesystem
man-db: /usr/lib/man-db/libman-2.7.6.1.so exists in filesystem
man-db: /usr/lib/man-db/libman.so exists in filesystem
man-db: /usr/lib/man-db/libmandb-2.7.6.1.so exists in filesystem
...
A simple query for what's wrong:
# pacman -Qkk man-db
man-db: 363 total files, 0 altered files
So, nothing wrong with it. It just loves busting my balls!
Using a bigger hammer:
# pacman -S --force man-db
...
:: Processing package changes...
(1/1) upgrading man-db [######################] 100%
New optional dependencies for man-db
gzip [installed]
:: Running post-transaction hooks...
(1/2) Creating temporary files...
(2/2) Arming ConditionNeedsUpdate...
Now my pacman -Syu works. Weird case, that.
Open Management Infrastructure in Azure gone wild
Thursday, January 25. 2018
I opened my mail, and I had 730 new e-mails there! Whaat!
One of my Azure boxes has (for reason unknown to me), following crontab-entry on root's crontab:
* * * * * [ \( ! -f /etc/opt/omi/creds/omi.keytab \) -o
\( /etc/krb5.keytab -nt /etc/opt/omi/creds/omi.keytab \) ] &&
/opt/omi/bin/support/ktstrip /etc/krb5.keytab /etc/opt/omi/creds/omi.keytab
/opt/omi/bin/support/ktstrip keeps failing, because /etc/krb5.keytab is missing. And that command is run every single minute on my machine. So, every single minute I get a new information about the failure. Nice!
The sequence of events is totally unclear to me. I haven't touched anything, but this morning an influx of e-mails stated pouring in.
OMI, or Open Management Infrastructure is something Linux-images in Azure have, so it shouldn't be anything dangerous.
The obvious fix as to remove that stupid line.
HOWTO: Configuring a router on a Mini-PC with CentOS
Thursday, January 18. 2018
Over half an year later, I realized, that I never published my article about operating system and software setup of my Mini-PC router. This is a follow-up post about the Qotom-hardware I wrote earlier. So, its probably about time to do that!
To get the ball rolling on new CentOS installation, a good start is to download it, Rufus it into an USB-stick and install the minimal setup into router-PC. The CentOS installation is so well documented and trivial process, I won't go into any details of it. Read something like Installing Red Hat Enterprise Linux 7.4 on all architectures for details of that.
Goal
Every project needs a goal. In any kind of engineering there is a specification and criteria, that the goal has been met.
The goal of this project is to create a Linux-server capable of securing a local network from the Internet and allow traffic to pass from the LAN to the wild-wild-net.
Spec:
- There is a working CentOS Linux running on the MiniPC
- ISP's cable modem is configured as bridge, no double NATting done
- MiniPC gets a public IP-address from ISP
- MiniPC can be accessed from the Net via the IP-address
- Configurations persist a reboot on the MiniPC
- MiniPC issues dynamic IP-addresses to LAN-clients
- MiniPC acts as a caching nameserver to LAN-clients
- Any requests from the Net are not served
- Wireless access point is configured not do do any routing, aka. it is in access point mode
- The setup is secure with attack surface minimized
- LAN IP-address range is 192.168.1.0/24
Definition of done:
- Internet works!
- MiniPC can connect to net
- MiniPC can be connected from net and LAN via SSH
- Wired clients can connect to net via Ethernet cable without any manual configuration
- Wireless clients can connec to the net via Wi-Fi without any manual configuration
Step 1: Packages
After minimal installation, the set of tools and packages required includes:
net-tools bind-utils screen tcpdump policycoreutils-python setools
- net-tools: mostly for netstat, using
routeorifconfigis deprecated - bind-utils: for dig and nslookup
- screen: for full-screen window manager
- tcpdump: taking a look into Ethernet and TCP/IP-packages, when something goes wrong, getting detailed view is very important
- policycoreutils-python setools: for managing SELinux
Step 2: Remove NetworkManager
Packages to install: -none needed-
Why a server would have GNOME NetworkManager installed on a server is beyond me. I simply cannot comprehend what CentOS-people are thinking, when they as default treat my server as a laptop. But the main thing is, that this piece of shit needs to go! The quicker, the better!
DANGER!
When you actually run the yum-command to remove NetworkManager, your system will lose all network connectivity. So, please, do run this at a console, not via SSH-connection.
DANGER!
Run command as root on console:
yum erase NetworkManager
Now your system's networking is royally messed up.
Step 3: Setup NICs
Packages to install: -none needed-
Check that NetworkManager created and left ifcfg-files into /etc/sysconfig/network-scripts/. If the appropriate ifcfg-files (one for each interface) are gone, you need to start learning how to write one fast. A good starting point on that would be RedHat Enterprise Linux 7 product documentation, Networking Guide, section 2.2 Editing Network Configuration Files.
LAN interface
Out of the two Ethernet-interfaces, 50/50 coin-flip ended as enp3s0 LAN and enp1s0 WAN. For any practical purposes, it really doesn't matter which one is which, but I'm describing here my setup. If you're using some other hardware, your interface names won't match those.
For any sensible use of your LAN-side, this interface should be connected to a network switch, so that your local network can be shared by your PC, Playstation, TV, Wi-Fi access point or whatever you have there running. Of course you can run it with only one host connected directly to the router.
This is critical: Your LAN-interface MUST have a static IP-address for it. It really cannot act as LAN-side of a router without one.
I chose my LAN to be private IP-range 192.168.1.0/24, so I edited /etc/sysconfig/network-scripts/ifcfg-enp3s0 to contain:
TYPE=Ethernet
BOOTPROTO=none
DEFROUTE=yes
IPV6INIT=yes
NAME=enp3s0
UUID=-don't-touch-this-
DEVICE=enp3s0
ONBOOT=yes
NETWORK=192.168.1.0
BROADCAST=193.168.1.255
USERCTL=no
IPADDR=192.168.1.1
PREFIX=24
IPV4_FAILURE_FATAL=no
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_PEERDNS=yes
IPV6_PEERROUTES=yes
IPV6_FAILURE_FATAL=no
WAN interface
For WAN, there is no need to touch enp1s0 setup (much). When your WAN-interface (enp1s0) starts, it will obtain an IP-address from your ISP. With that, it will also get your ISP's DNS-address an overwrite your precious manual changes in /etc/resolv.conf. You don't want that to happen. So, prevent that and edit /etc/sysconfig/network-scripts/ifcfg-enp1s0 and add:
PEERDNS="no"
Well, that was easy!
IP-forwarding
For routing to work, it requires Linux kernel to have IP-forwarding enabled. It will allow network packets to travel between interfaces.
Enable IP-forwarding immediately:
sysctl -w net.ipv4.ip_forward=1
Enable IP-forwarding on boot:
sysctl net.ipv4.ip_forward > /etc/sysctl.d/1_ip_forward.conf
Finalize network setup
When your network interface configurations are ok, restart everything by running following as root:
systemctl enable network
systemctl restart network
Now your system:
- has both interfaces on-line
- is reachable from a machine on your wired-LAN using a static IP-address other than 192.168.1.1.
Note: your router doesn'ht have DHCPd running yet, so you need to figure out how to configure a static IP-address to your device - still gets an IP-address from your ISP from your external interface
- can reach IP-addresses via both external and internal interfaces
If these criteria are not met, there is simply no point in proceeding. Your system won't work as a router without those prerequisites.
Finally, make sure that your IPtables-rules have effect. Your box is connected to Internet and it can be accessed/bombarded from there, so run following to secure your setup:
systemctl restart firewalld
Now your system is ready to become a router.
Step 4: Firewalld
Packages to install: -none needed-
Zones
Out-of-box CentOS has firewalld enabled. It has only one zone defined for public wild-wild-net, also TCP/22 SSH is open for the world. This needs to be run as root. First split off LAN into own zone home:
# firewall-cmd --zone home --change-interface enp3s0 --permanent
Check the zones and their assigned interfaces:
# firewall-cmd --get-active-zones
home
interfaces: enp3s0
public
interfaces: enp1s0
Setup network address translation (NAT) and allow traffic to flow from your LAN to outside world. Any relevant traffic is allowed to flow in from Internet back to your LAN. Commands to run:
# firewall-cmd --permanent --direct --add-rule ipv4 nat POSTROUTING 0 -o enp1s0 -j MASQUERADE
# firewall-cmd --permanent --direct --add-rule ipv4 filter FWDI_home_allow 0 -o enp1s0 -j ACCEPT
# firewall-cmd --permanent --direct --add-rule ipv4 filter FWDI_public_allow 0 -o enp3s0 -m state --state RELATED,ESTABLISHED -j ACCEPT
Enable the DNS-server we'll setup later, also disable any outgoing DNS-queries from your LAN (a security measure):
# firewall-cmd --permanent --zone home --add-service dns
# firewall-cmd --permanent --direct --add-rule ipv4 filter FWDI_home_deny 0 -p udp -m udp --dport 53 -j REJECT
At this point do a reload:
# firewall-cmd --reload
... and test your firewall setup from router:
- You still must be able to access Internet from your router
- Your LAN does work at this point. A client with a static IP must be able to access Internet.
Step 5: Named
Packages to install: bind-chroot
You can continue to use your ISP's nameserver, but I never do that. It makes much more sense to have a caching nameserver running at your own router. This allows your box to go directly to Internet root servers and do all the name queries for you. In many countries ISPs intentionally drop some domains out or are forced by government to do that. Running your own resolver makes sure that you get all the records as is and in case of changes you can flush caches whenever you want and don't have to wait for a record to expire.Out-of-box the BIND 9.9.4 does not server anybody else than localhost. To fix this, find following two lines in /etc/named.conf:
listen-on port 53 { 127.0.0.1; };
allow-query { localhost; };
Edit them to contain:
listen-on port 53 { 127.0.0.1; 192.168.1.1; };
allow-query { localhost; 192.168.1.0/24; };
Finally, change your system's default name resolver by editing /etc/resolv.conf to contain a single line:
nameserver 127.0.0.1
Start the server and enable it to start on boot:
systemctl start named-chroot
systemctl enable named-chroot
Now you're ready to test the setup. Just host www.google.com or your favorite site. Successful reply will include IP-address(es) for your query.
Step 6: DHCP
Packages to install: dhcp
Edit/etc/dhcp/dhcpd.conf and have it contain:
ddns-update-style interim;
ignore client-updates;
authoritative;
default-lease-time 14400;
max-lease-time 86400;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option routers 192.168.1.1;
option domain-name "my.own.lan";
option domain-name-servers 192.168.1.1;
subnet 192.168.1.0 netmask 255.255.255.0 {
range 192.168.1.50 192.168.1.99;
}
That piece of configuration will use your router as DNS for the clients and issue them addresses from range .50 - .99.
Start the server and enable it to start on boot:
systemctl start dhcpd
systemctl enable dhcpd
At this point, configure your client to use DHCP for IP-addressing. You must get an IP from the above range, also DNS-resolve and NAT should work, but that's the next step to do. Test it all.
Step 7: Testing it
Make sure:
- A client in your LAN gets an IP-address from DHCP
- A client in your LAN can ping your router at 192.168.1.1
- A client in your LAN can ping something in the Internet, like Google's name server at 8.8.8.8
- A client in your LAN resolves names, for example:
nslookup www.google.comreturns IP-addresses - A client in your LAN can access https://www.google.com/ via a web-browser
That's it! What else would you need?
Done!
Congratulations on your new router!
What I did next was set up my own DNS-zone so that my hosts had FQDNs. But that's beyond this blog post. Read something like How To Configure BIND as a Private Network DNS Server on CentOS 7 by DigitalOcean for that.
Windows 10 Fall Creators Update breaking sleep
Monday, December 18. 2017
Problem
My gaming PC got the fall update quite late and after that it wouldn't stay in sleep. Something got broken in the update and I had to shut it down every single time I didn't want to use it. Annoying!
Debugging - The Reason
The reason it popped back on wasn't big of a mystery. There is a simple command to query the wake reason:
PS C:\WINDOWS\system32> .\powercfg.exe /waketimers
Timer set by [SERVICE] \Device\HarddiskVolume4\Windows\System32\svchost.exe (SystemEventsBroker) expires at 21:46:29 on 15.12.2017.
Reason: Windows will execute 'NT TASK\Microsoft\Windows\UpdateOrchestrator\Reboot' scheduled task that requested waking the computer.
There are number of articles about How to disable wake timers?, but it doesn't fix this.
A peek into Windows Task Scheduler reveals the ugly fact:
There is a hourly scheduled task, that indeed does run every hour and every goddamn hour it will wake my computer from the sleep to see if it needs to reboot it! Who having half a brain made that engineering decision at Microsoft?!
Attempt 1 - Disable the task - FAIL!
Ok, easy thing, let's disable the task. Or ... let's not. It is impossible! The permissions prevent regular human beings from doing that.
After a while, I bumped into somebody else having this same particular problem. Computer is waking up and: Can't modify task “Reboot” in win10 home. Basically, the idea is to go get Sysinternals PStools. It contains a tool called PSexec, which can do the modification for you.
Like this:
First run a cmd.exe with the PSexec 64-bit version:
PS D:\Users\Downloads> .\PsExec64.exe /s cmd.exe
Now, that permission-barrier is fixed, then:
C:\WINDOWS\system32>schtasks /change /tn "\Microsoft\Windows\UpdateOrchestrator\Reboot" /disable
SUCCESS: The parameters of scheduled task "\Microsoft\Windows\UpdateOrchestrator\Reboot" have been changed.
Now the stupid scheduled task is running hourly as expected, but NOT when your computer is sleeping. But ... guess what! Yes! There is something in Windows 10 internals, that keeps that particular task enabled. It will stay disabled for half an hour or so, but ultimately just using the computer makes the task enabled again, and the problem persists.
Attempt 2 - Remove the allow wake setting - FAIL!
By using the PsExec64.exe-trick, it is possible to get an XML-representation of the task, by running:
schtasks /tn "\Microsoft\Windows\UpdateOrchestrator\Reboot" /xml
in the XML-data there is:
<WakeToRun>true</WakeToRun>
... but I don't know how to change a task from XML-file. You can create a new one, but changing seems impossible.
So, ultimately I had to find something else
Attempt 3 - Powershell - FAIL!
Instead of spawning a new cmd.exe, going for PowerShell has benefits - it can actually edit an existing task. There is a built-in applet Get-ScheduledTask, with appropriate counterpart for setting the properties.
Spawn a nice PowerShell-session with appropriate permissions:
.\PsExec64.exe /s powershell.exe
The shell is kinda dead, for example output is garbled and input editing has issues, but if you know what to run, it will do it given the correct permissions.
As suggested in use powershell to find scheduled tasks set to wake the computer, now it is possible to get a list of Scheduled Tasks which have permission to wake the computer:
PS C:\WINDOWS\system32> Get-ScheduledTask | where {$_.settings.waketorun}
My computer will output a list like:
TaskPath TaskName
-------- --------
\Microsoft\Windows\.NET Framework\ .NET Framework NGEN v4.0.3031...
\Microsoft\Windows\.NET Framework\ .NET Framework NGEN v4.0.3031...
\Microsoft\Windows\SharedPC\ Account Cleanup
\Microsoft\Windows\UpdateOrchestrator\ Reboot
A simple(?) one-liner will edit the task (backtick is the word-wrap operator):
Get-ScheduledTask `
-TaskPath \Microsoft\Windows\UpdateOrchestrator\ `
-TaskName Reboot |
%{ $_.Settings.WakeToRun = $false ; `
Set-ScheduledTask -TaskName $_.TaskName -TaskPath $_.TaskPath -Settings $_.Settings }
Yes, now the task is enabled, but has the appropriate condition setting for allow wake the computer from sleep disabled.
... aaaand it doesn't work. The same thing altering the enabled-state also resets this setting. Darn!
Attempt 4 - Revoke permissions - Success!
This was driving me mad!
It worked perfectly before the stupid update!
Finally, I found an article from Reddit: Is there ANY way to stop UpdateOrchestrator for turning 'wake the computer to run this task' back on after every cumulative update?
That guy suggested to revoke all permissions from the file. Now the automator which keeps resetting the settings fails to touch the file.
The command I ran in PowerShell is:
icacls $env:windir"\System32\Tasks\Microsoft\Windows\UpdateOrchestrator\Reboot" `
/inheritance:r `
/deny "Everyone:F" `
/deny "SYSTEM:F" `
/deny "Local Service:F" `
/deny "Administrators:F"
That simply puts everybody and everything into deny-list for the file-access. AND IT WORKS!
So, looks like ultimately whatever the mechanism is restoring the setting, somebody loves writing to the file, but it doesn't know how to reset the permissions. Which is nice!
I chose to keep the task enabled, but unset the allow wake -setting. So, when my computer is running, the task is ran every hour as expected, but when my computer is sleeping, my computer is sleeping and doesn't wake for nobody.
Microsoft:
Suggestion, eat your own dog food! If anybody at the Windows-team doing power management/task scheduler would run this at home they would know the annoyance instantly.
Saving the day - Android tethering with Linux
Sunday, December 3. 2017
The fail
On a peaceful Sunday, I was just minding my own business and BOOM! Internet connection was gone. After a quick debugging session, restarting the router and eyeballing the LEDs, it was evident: something with my ISP Com Hem was down:
Ok, ISP down, what next?
I whipped up the iPhone and went for any possible service announcements. And yes, the above announcement was placed on my user account information. I was stunned by this, it was so cool to have:
- confirmation, that something was down with ISP: Yup, it's broken.
- that information tailored with the geographical location of my subscription: Yup, that fail affects you.
No Finnish ISP or telco has that. I was very impressed with such detail (and still am).
The fix
There is no way I'm sitting on my thumbs on such an event. I was just about to start playing Need for Speed and now Origin wouldn't even log me in, so, no Internet, no gaming.
I have an el-cheapo Huawei Android lying around somewhere, with a Swedish SIM-card in it. My dirt cheap subscription has couple of gigs data transfer per month in it, which I never use. I came up with a plan to temporarily use the cell phone as an Internet connection. The idea would be to hook it up into my Linux router with an USB-cable, make sure the Android pops up as a network interface and then configure the Linux to use that network interface as primary connection.
Thethering
I found tons of information about Android-tethering from Arch Linux wiki. It basically says:
- Make sure your Android is newer than 2.2
- Connect the phone to a Linux
- Enable USB-tethering from the phone's connection sharing -menu
- Confirm the new network interface's existence on the Linux end
On my phone, there was two settings for personal hotspot. Wifi/Bluetooth and USB:
Connection
New phones have USB-C, but its such a new connector type, that anything older than couple years, has most likely micro-USB -connector:
Hooking it up to a Linux will output tons of dmesg and and ultimately result in a brand new network interface:
# ip addr show
5: enp0s20u4u3:
link/ether 82:49:a8:b4:96:c9 brd ff:ff:ff:ff:f
inet 192.168.42.90/24 brd 192.168.42.255 scope
valid_lft 3595sec preferred_lft 3595sec
inet6 fe80::7762:e1a9:9fa:69f5/64 scope link
valid_lft forever preferred_lft forever
Routing configuration
Now that there was a new connection, I tried pinging something in the wild world:
ping -I enp0s20u4u3 193.166.3.2
Nope. Didn't work.
I confirmed, that the default network gateway was still set up into the broken link:
# ip route show
default via 192.168.100.1 dev enp1s0 proto static metric 100
That needs to go to enable some functionality. But what to replace the bad gateway with?
Since the connection had IP-address from Telco DHCP, there is a lease-file with all the necessary information:
# cat /var/lib/NetworkManager/dhclient-*-enp0s20u4u3.lease
lease {
interface "enp0s20u4u3";
fixed-address 192.168.42.90;
option subnet-mask 255.255.255.0;
option routers 192.168.42.129;
The fixed-address in the file matches the above ip addr show -information. Required information was gathered, and the idea was to ditch the original gateway and replace it with a one from the Android phone's telco:
# ip route del default via 192.168.100.1
# ip route add default via 192.168.42.129 dev enp0s20u4u3
# ip route show
default via 192.168.42.129 dev enp0s20u4u3 proto static metric 101
Now it started cooking:
# ping -c 5 ftp.funet.fi
PING ftp.funet.fi (193.166.3.2) 56(84) bytes of data.
64 bytes from ftp.funet.fi (193.166.3.2): icmp_seq=1 ttl=242 time=35.6 ms
64 bytes from ftp.funet.fi (193.166.3.2): icmp_seq=2 ttl=242 time=31.7 ms
To finalize the access from my LAN, I ran following firewall-cmd --direct commands:
--remove-rule ipv4 nat POSTROUTING 0 -o enp1s0 -j MASQUERADE
--add-rule ipv4 nat POSTROUTING 0 -o enp0s20u4u3 -j MASQUERADE
--add-rule ipv4 filter FORWARD 0 -i enp3s0 -o enp0s20u4u3 -j ACCEPT
--add-rule ipv4 filter FORWARD 0 -i enp0s20u4u3 -o enp3s0 \
-m state --state RELATED,ESTABLISHED -j ACCEPT
There is no firewall-cmd --permanent on purpose. I don't intend those to stick too long. I just wanted to play the darn game!
Done!
Now my gaming PC would connect to The Big Net. I could suft the web, read mail and even Origin logged me in.
That's it! Day saved!
