Category Archives: CLI

CLI

Setup remote git repository with SSH & GIT

Leave a comment

I wanted to set up a simple git repository to synchronize my bash scripts between a couple hosts, no fancy github or gitlab software required. These are my notes on how I got it working. Thanks to this site for the information.

On the remote host (server)

mkdir GIT_PROJECT_DIR.git
cd GIT_PROJECT_DIR.git
git init --bare

On the local hosts (client)

Create a git repository and add files to it:

cd GIT_FOLDER
git init
git add *
git commit -m "Initial commit"
git remote add origin USER@REMOTE_HOST:GIT_PROJECT_DIR.git
git push origin master
git branch --set-upstream-to=origin/master
CLI

Modify network buffers in Linux using sysctl

Leave a comment

After installing Netdata I kept getting alerts that packets were being dropped. After some research I read you can alleviate this by increasing your system’s networking buffer. You can accomplish this with sysctl.

If you run sysctl manually it will not survive a reboot. If you want persistence you simply add the sysctl command line to /etc/sysctl.conf. Thanks to Brennen Smith on serverfault for the info on my particular problem with UDP drops:

#as root:
echo "net.core.rmem_default=8388608" >> /etc/sysctl.conf
echo "net.core.rmem_max=16777216" >> /etc/sysctl.conf
sysctl -p

The above solved my udp problem but you can modify it to change any sysctl things you want to quickly configure and persist.

CLI, OS

Mount encfs folder on startup with systemd

2 Comments

A quick note on how to encrypt a folder with encfs and then mount it on boot via a systemd startup script. In my case the folder is located on a network drive and I wanted it to happen whether I was logged in or not.

Create encfs folder:

encfs <path to encrypted folder> <path to mount decrypted folder>

Follow the prompts to create the folder and set a password.

Next create a file which will contain your decryption password

echo "YOUR_PASSWORD" > /home/user/super_secret_password_location
chmod 700 /home/user/super_secret_password_location

Create a simple script to be called by systemd on startup using cat to pass your password over to encfs

#!/bin/bash
cat super_secret_password_location | encfs -S path_to_encrypted_folder path_to_mount_decrypted_folder

Finally create a systemd unit to run your script on startup:

vim /etc/systemd/system/mount-encrypted.service
[Unit] 
Description=Mount encrypted folder 
After=network.target 

[Service] 
User=<YOUR USER> 
Type=oneshot 
ExecStartPre=/bin/sleep 20 
ExecStart=PATH_TO_SCRIPT
TimeoutStopSec=30 
KillMode=process 

[Install] 
WantedBy=multi-user.target

Then enable the unit:

sudo systemctl daemon-reload
sudo systemctl enable mount-encrypted.service
CLI, Virtualization

CPU Pinning in Proxmox

3 Comments

Proxmox uses qemu which doesn’t implement CPU pinning by itself. If you want to limit a guest VM’s operations to specific CPU cores on the host you need to use taskset. It was a bit confusing to figure out but fortunately I found this gist by ayufan which handles it beautifully.

Save the following into taskset.sh and edit VMID to the ID of the VM you wish to pin CPUs to. Make sure you have the “expect” package installed.

#!/bin/bash

set -eo pipefail

VMID=200

cpu_tasks() {
	expect <<EOF | sed -n 's/^.* CPU .*thread_id=\(.*\)$/\1/p' | tr -d '\r' || true
spawn qm monitor $VMID
expect ">"
send "info cpus\r"
expect ">"
EOF
}

VCPUS=($(cpu_tasks))
VCPU_COUNT="${#VCPUS[@]}"

if [[ $VCPU_COUNT -eq 0 ]]; then
	echo "* No VCPUS for VM$VMID"
	exit 1
fi

echo "* Detected ${#VCPUS[@]} assigned to VM$VMID..."
echo "* Resetting cpu shield..."

for CPU_INDEX in "${!VCPUS[@]}"
do
	CPU_TASK="${VCPUS[$CPU_INDEX]}"
	echo "* Assigning $CPU_INDEX to $CPU_TASK..."
	taskset -pc "$CPU_INDEX" "$CPU_TASK"
done

Update 9/29/18: Fixed missing done at the end. Also if you want to offset which cores this script uses, you can do so by modifying  the $CPU_INDEX variable to do a bit of math, like so:

        taskset -pc "$[CPU_INDEX+16]"

The above adds 16 to each process ID, so instead of staring on thread 0 it starts on thread 16.

CLI, Hardware, OS

Fix USB bluetooth in KDE Plasma on CentOS 7

Leave a comment

I spent too many hours trying to figure this stupid thing out.. but FINALLY! I have my bluetooth headset working in CentOS 7 with the KDE 4 Plasma environment. Read on if you dare…

First, you must configure dbus to allow your user to use the bluetooth dongle. Add the following above the closing /busconfig tag.  Be sure to replace USERNAME with your user account:

sudo nano /etc/dbus-1/system.d/bluetooth.conf
  <policy user="USERNAME">
    <allow send_destination="org.bluez"/>
    <allow send_interface="org.bluez.Agent1"/>
    <allow send_interface="org.bluez.GattCharacteristic1"/>
    <allow send_interface="org.bluez.GattDescriptor1"/>
    <allow send_interface="org.freedesktop.DBus.ObjectManager"/>
    <allow send_interface="org.freedesktop.DBus.Properties"/>
  </policy>

Remove and re-plug the adapter in.

Next, follow Arch Linux’s excellent guide on how to pair a bluetooth device using bluetoothctl

bluetoothctl
[bluetooth]# power on
[bluetooth]# agent on
[bluetooth]# default-agent
[bluetooth]# scan on

Now make sure that your headset is in pairing mode. It should be discovered shortly. For example,

[NEW] Device 00:1D:43:6D:03:26 Lasmex LBT10

shows a device that calls itself “Lasmex LBT10” and has MAC address “00:1D:43:6D:03:26”. We will now use that MAC address to initiate the pairing:

[bluetooth]# pair 00:1D:43:6D:03:26

After pairing, you also need to explicitly connect the device (every time?):

[bluetooth]# connect 00:1D:43:6D:03:26

If you’re getting a connection error org.bluez.Error.Failed retry by killing existing PulseAudio daemon first:

$ pulseaudio -k
[bluetooth]# connect 00:1D:43:6D:03:26

Finally, configure pulseaudio to automatically switch all audio to your headset by adding the following line to the bottom of /etc/pulse/default.pa:

nano /etc/pulse/default.pa

# automatically switch to newly-connected devices
load-module module-switch-on-connect

Update 7/27: I rebooted my machine and lost my bluetooth, to my dismay. I discovered that my user needs to be a member of the audio group. Since I’m in an active directory environment I think the local audio group got removed at reboot. So, to restore it, as root I had to run this:

usermod -aG audio <user>

After doing that, to prevent logging out and back in again, you can do the following:

su - <USERNAME>

Once that’s done all the bluetoothctl commands worked again.

CLI, OS, Virtualization

Backup and restore docker container configurations

1 Comment

I came across a need to start afresh with my docker setup. I didn’t want to re-create all the port and volume mappings for my various containers. Fortunately I found a way around this by using docker-autocompose to create .yml files with all my settings and docker-compose to restore them to my new docker host.

Backup

Docker-autocompose source: https://github.com/Red5d/docker-autocompose

git clone https://github.com/Red5d/docker-autocompose.git
cd docker-autocompose
docker build -t red5d/docker-autocompose .

With docker-autocompose created you can then use it to create .yml files for each of your running containers by utilizing a simple BASH for loop:

for image in $(docker ps --format '{{.Names}}'); do docker run -v /var/run/docker.sock:/var/run/docker.sock red5d/docker-autocompose $image > $image.yml; done

Simple.

Restore

To restore, install and use docker-compose:

sudo curl -L https://github.com/docker/compose/releases/download/1.21.2/docker-compose-$(uname -s)-$(uname -m) -o /usr/local/bin/docker-compose
sudo chmod +x /usr/local/bin/docker-compose

Next we use another simple for loop to go through each .yml file and import them into Docker. The sed piece escapes any $ characters in the .yml files so they will import properly.

for file in *.yml; do sed 's/\$/\$\$/g' -i $file;
docker-compose -f $file up --force-recreate -d; done

You can safely ignore the warnings about orphans.

That’s it!

Troubleshooting

ERROR: Invalid interpolation format for “environment” option in service “Transmission”: “PS1=$(whoami)@$(hostname):$(pwd)$ “

This is due to .yml files which contain unescaped $ characters.

Escape any $ with another $ using sed

sed 's/\$/\$\$/g' -i <filename>.yml

ERROR: The Compose file ‘./MariaDB.yml’ is invalid because:
MariaDB.user contains an invalid type, it should be a string

My MariaDB docker .yml file had a user: environment variable that was a number, which docker compose interpreted as a number instead of a string. I had to modify that particular .yml file and add quotes around the value that I had for the User environment variable.

CLI

Accept multiple SSH RSA keys with ssh-keyscan

Leave a comment

I came across a new machine that needed to connect to many SSH hosts via ansible. I had a problem where ansible was prompting me for each post if I wanted to accept the RSA key. As I had dozens of hosts I didn’t want to type yes for every single one; furthermore the yes command didn’t appear to work. I needed a way to automatically accept all SSH RSA keys from a list of server names. I know you can disable RSA key checking but I didn’t want to do that.

I eventually found this site which suggested a small for loop, which did the trick beautifully. I modified it to suit my needs.

This little two-liner takes a file (in my case, my ansible hosts file) and then runs ssh-keyscan against it and adds the results to the .ssh/known_hosts file. The end result is an automated way to accept many SSH keys.

SERVER_LIST=$(cat /etc/ansible/hosts)
for host in $SERVER_LIST; do ssh-keyscan -H $host >> ~/.ssh/known_hosts; done
CLI, Hardware

Using a Bus Pirate to fix Seagate drives

1 Comment

I wrote these notes almost three years ago but never published them. Since I’ve now referenced them again I’ll publish them albeit in a crude state.

7200.11 BSY bug

I had a need to fix the firmware of a Seagate  7200.11 BSY bug, which involved connecting to the RS232 serial ports on the drive and issuing a few commands to clear SMART data. Details here:

http://www.arvydas.co.uk/2012/07/fixing-a-seagate-7200-11-hard-drive-with-arduino/

http://hackaday.com/2012/07/30/recovering-from-a-seagate-hdd-firmware-bug/

https://plus.google.com/u/0/+BillFarrow/posts/ir1xnfu46TE

http://webcache.googleusercontent.com/search?q=cache:F1J2P5E3mrIJ:haquesprojects.com/embedded-device-hacking/using-a-bus-pirate-as-a-usb-ttl-serial-converter/+&cd=4&hl=en&ct=clnk&gl=us

http://fillwithcoolblogname.blogspot.com/2011/02/fixing-seagate-720011-bsy-0-lba-fw-bug.html

Using a Bus Pirate:

Find out what device the bus pirate is given:

dmesg | tail

usb 1-1.6.3: FTDI USB Serial Device converter now attached to ttyUSB0

Next, add your user to the dialout group (thanks to here for the hint)

usermod -a -G dialout $USER

You may need to log out and log back in after issuing the above command for it to take effect.

Fire up a terminal editor (I used screen after learning about my options from here.)

screen /dev/ttyUSB0 115200 8N1

Press Enter and you should be greeted with the Bus Pirate’s HiZ> prompt. Next, enter the following:

1. m – to change the mode
2. 3 – for UART mode
3. 7 – for 38400 bps
4. 1 – for 8 bits of data, no parity control
5. 1 – for 1 stop bit
6. 1 – for Idle 1 receive polarity
7. 2 – for Normal output type

At the “UART>” prompt. Enter “(0)” to show available macros:

UART>(0)
0.Macro menu
1.Transparent bridge
2.Live monitor
3.Bridge with flow control

Now enter “(3)”  (don’t forget the parenthesis – this burned me) to enter bridge mode with flow control and hit “y” at the “Are you sure?” prompt. The terminal will receive input from your device.

UART>(3)
UART bridge
Reset to exit
Are you sure?

Now plug in pins to hard drive. Use this site as a guide for which pins to use. The drive should be upside down to expose the controller board.
BP Gnd (top left) to Gnd on drive (Second pin from the left)
BP MISO (UART RX – bottom right) to TX on drive (far right pin)
BP MOSI (UART TX) to RX on drive (Seconf from the right pin)

I only ended up needing MISO & MOSI, ground wasn’t required.

Un-screw hard drive, add shim to prevent electrical contact

Power on drive

CTRL+Z

/2

(wait 30 seconds)

Z

(un-shim, re-screw hard drive)

U

/1

N1

Power down drive, wait few seconds, power back up

CTRL + Z

m0,2,2,0,0,0,0,22 (enter)

Clear SMART data

A couple years later I came across some old NAS drives that I wanted to use. I ran a full battery of burn-in tests using badblocks and the drives passed with flying colors. The only problem is they had SMART data saying Reallocated_Sector_Ct was past the threshold. Barely. I decided to roll the dice with these drives anyway given their proven performance currently and over the years.

The problem is FreeNAS will e-mail spam you about that SMART attribute. I couldn’t find a good way to suppress those alerts yet have them alert if that number gets worse, so I decided to cheat and clear all SMART data from those drives, thus getting FreeNAS happy with me yet alerting me if the reallocated sector count increases in the future.

I read a few sources to accomplish this with my bus pirate.

https://blog.zencoffee.org/2011/07/bus-pirate-as-ftdi-cable/

https://forum.hddguru.com/viewtopic.php?f=1&t=33886&start=20&mobile=mobile

https://forum.hddguru.com/viewtopic.php?f=1&t=33886&start=20

Use the same instructions as above for hooking up the bus pirate to the drive’s RS232 ports (to the right of the SATA port.)

Once you’ve serial connected to the drive, it’s three simple commands to clear the SMART data:

CTRL + Z
/1
N1
CLI, OS

CentOS 7 Enterprise desktop setup

Leave a comment

These are my notes for standing up a CentOS 7 desktop in an enterprise environment.

Packages

Install the EPEL repository for a better experience:

sudo yum -y install epel-release

Desktop experience packages:

sudo yum -y install vlc libreoffice java gstreamer gstreamer1 gstreamer-ffmpeg gstreamer-plugins-good gstreamer-plugins-ugly gstreamer1-plugins-bad-freeworld gstreamer1-libav pidgin rhythmbox ffmpeg keepass xdotool ntfs-3g gvfs-fuse gvfs-smb fuse sshfs redshift-gtk stoken-gui stoken-cli

Additional packages that may come in handy

sudo yum -y install http://li.nux.ro/download/nux/dextop/el7/x86_64/nux-dextop-release-0-5.el7.nux.noarch.rpm
sudo yum -y install libdvdcss gstreamer{,1}-plugins-ugly gstreamer-plugins-bad-nonfree gstreamer1-plugins-bad-freeworld libde265 x265

Enable ssh:

sudo systemctl enable sshd
sudo systemctl start sshd

Google Chrome

Paste into /etc/yum.repos.d/google-chrome.repo:

[google64]
name=Google - x86_64
baseurl=http://dl.google.com/linux/rpm/stable/x86_64
enabled=1
gpgcheck=1
gpgkey=https://dl-ssl.google.com/linux/linux_signing_key.pub
sudo yum -y install google-chrome-stable

Domain

It’s just easier to use PowerBroker Open from beyondtrust

sudo wget -O /etc/yum.repos.d/pbiso.repo http://repo.pbis.beyondtrust.com/yum/pbiso.repo
sudo yum -y install pbis-open

Cliff notes for joining the domain:

domainname=<your_domain_name>
domain_prefix=<your_domain_netbios_name>
domainaccount=<your_domain_admin_account

sudo domainjoin-cli join $domainname $domainaccount 
<enter password>

sudo /opt/pbis/bin/config UserDomainPrefix $domain_prefix
sudo /opt/pbis/bin/config AssumeDefaultDomain true
sudo /opt/pbis/bin/config LoginShellTemplate /bin/bash
sudo /opt/pbis/bin/config HomeDirTemplate %H/%U

Add domain admins to sudo, escaping spaces with a backlsash and replacing DOMAIN with your domain:

sudo visudo
%DOMAIN\\Domain\ Administrators ALL=(ALL) ALL

Reboot to make all changes go into effect.

Certificate

You might need to copy your domain’s CA certificate to your certificate trust store:

sudo cp <CA CERT FILENAME> /etc/pki/ca-trust/source/anchors/
sudo update-ca-trust

Drive mapping

I use a simple script to use gvfs-mount to mount network drives. Change suffix to match your domain and mounts to suit your needs.

#!/bin/bash
#Simple script to mount network drives on login

suffix=<DOMAIN_SUFFIX>
MOUNTS=(
	server1$suffix/folder1
	server2$suffix/folder2
        server3$suffix/folder3
)

for i in "${MOUNTS[@]}" 
do
	gvfs-mount "smb://$i"
done

Configure in gnome to run on startup:

Add the following to ~/.config/autostart/mount-drives.desktop, changing Exec= to the path of the above script.

[Desktop Entry]
Name=Mount network drives
GenericName=Mount network drives
Comment=Script to mount network drives
Exec=<location of mount script>
Terminal=false
Type=Application
X-GNOME-Autostart-enabled=true

Network Config

If you wish to add static IP and configure your DNS suffix (search domain) then run

nm-connection-editor

The other GUI for network configuration doesn’t have an option for search domains for some reason.

Smartcard

sudo yum -y install opensc pcsc-tools pcsc-lite

Be sure to install the drivers for your particular card reader. Mine came from here and here.

After installing you can test by starting pcscd and using pcsc_scan

sudo systemctl start pcscd
pcsc_scan

Vmware horizon view

Smartcard support

There is a problem with how the VMware View interacts with the opensc smartcard drivers shipped in popular Linux distributions such as CentOS and Ubuntu. View cannot load the drivers in the default configuration; therefore in order to get VMware View working with smartcards you need manually patch and compile the opensc package (thanks to this site for the information needed to do so.)

First, install the necessary development packages

sudo yum -y groupinstall "Development Tools"
sudo yum -y install openssl-devel pcsc-lite-devel

Next, download and extract opensc-0.13 from sourceforge:

wget http://downloads.sourceforge.net/project/opensc/OpenSC/opensc-0.13.0/opensc-0.13.0.tar.gz
tar zxvf opensc-0.13.0.tar.gz
cd opensc-0.13.0

Now we have to patch two specific files in the source before compiling:

echo "--- ./src/pkcs11/opensc-pkcs11.exports
 +++ ./src/pkcs11/opensc-pkcs11.exports
 @@ -1 +1,3 @@
  C_GetFunctionList
 +C_Initialize
 +C_Finalize
 --- ./src/pkcs11/pkcs11-spy.exports
 +++ ./src/pkcs11/pkcs11-spy.exports
 @@ -1 +1,3 @@
  C_GetFunctionList
 +C_Initialize
 +C_Finalize" > opensc.patch

patch -p1 -i opensc.patch

Next, compiling and installing:

./bootstrap
./configure
make
sudo make install

Assuming there were no errors, you can now link the compiled driver to the location VMware view expects it. Note: you must rename the library from opensc-pkcs11.so to libopensc-pkcs11.so for this to work (another lovely VMware bug)

sudo mkdir -p /usr/lib/vmware/view/pkcs11/
sudo ln -s /usr/local/lib/pkcs11/opensc-pkcs11.so /usr/lib/vmware/view/pkcs11/libopensc-pkcs11.so

Lync

Install the pidgin-sipe plugin as detailed here

sudo yum -y install pidgin pidgin-sipe

Choose “Office Communicator” as the protocol. Enter your e-mail address for the username, then go to the Advanced tab and check “Use single sign-on.”

On first run all contact names were missing. Per here, simply close and restart the application.

Gnome 3

Disable audible bell

Taken from here

Disable audible bell and enable visual bell with:

gsettings set org.gnome.desktop.wm.preferences audible-bell false
gsettings set org.gnome.desktop.wm.preferences visual-bell true

and change the type of the visual bell if you don’t need the fullscreen flash:

gsettings set org.gnome.desktop.wm.preferences visual-bell-type frame-flash

Extensions

If you can find your extension via yum it tends to work better than the gnome extension site. Make sure you’re using the correct shell version from the site:

gnome-shell --version
sudo yum -y install gnome-shell-extension-top-icons gnome-shell-extension-dash-to-dock

Other useful extensions:

backslide, multi monitors add-on , No topleft hot corner, Dropdown terminal, Media player indicator, Focus my window, Workspace indicator, Native window placement, Openweather, Panel osd, Dash to dock, Gpaste

RSA

For if you have the misfortune of being in an environment that uses RSA SecurID for two factor authentication, here is the official guide

Necessary packages to be installed:

sudo yum -y install selinux-policy-devel policycoreutils-devel
  1.  Download & extract PAM agent, cd to extracted directory 
    tar -xvf PAM-Agent*.tar
  2. Create /var/ace directory and place necessary files inside. Create sdopts.rec and add the IP address of the desktop. 
    mkdir /var/ace
cp sdconf.rec /var/ace
vi /var/ace/sdopts.rec
CLIENT_IP=<IP ADDRESS OF DESKTOP>
  3. Run the install_pam script and specify UDP authentication 
    ./install_pam.sh
  4.  Modify /etc/pam.d/password-auth to add the RSA authentication agent. Insert above pam_lsass.so smartcard_prompt try_first_pass line, then comment out pam_lsass.so smartcard_prompt try_first_pass line 
    auth required pam_securid.so
auth required pam_env.so
auth sufficient pam_lsass.so
  5. Add new system in RSA console: Access / Authentication Agents / Add new
  6. Test to make sure everything works: 
    /opt/pam/bin/64bit/acetest
CLI, OS

Managing Windows hosts with Ansible

Leave a comment

I spun my wheels for a while trying to get Ansible to manage windows hosts. Here are my notes on how I finally successfully got ansible (on a Linux host) to use an HTTPS WinRM connection to connect to a windows host using Kerberos for authentication. This article was of great help.

Ansible Hosts file

[all:vars]
ansible_user=<user>
ansible_password=<password>
ansible_connection=winrm
ansible_winrm_transport=kerberos

Packages to install (CentOS 7)

sudo yum install gcc python2-pip
sudo pip install kerberos requests_kerberos pywinrm certifi

Playbook syntax

Modules involving Windows hosts have a win_ prefix.

Troubleshooting

Code 500

WinRMTransportError: (u'http', u'Bad
HTTP response returned from server. Code 500')

I was using -m ping for testing instead of -m win_ping. Make sure you’re using win_ping and not regular ping module.

Certificate validation failed

"msg": "kerberos: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:579)"

I had a self signed CA certificate on the box ansible was trying to connect to. Python doesn’t appear to trust the system’s certificate trust chain by default. Ansible has a configuration directive

ansible_winrm_ca_trust_path

but even with that pointing to my system trust it wouldn’t work. I then found this gem on the winrm page for ansible:

The CA chain can contain a single or multiple issuer certificates and each entry is contained on a new line. To then use the custom CA chain as part of the validation process, set ansible_winrm_ca_trust_path to the path of the file. If this variable is not set, the default CA chain is used instead which is located in the install path of the Python package certifi.

Challenge #1: I didn’t have certifi installed.

sudo pip install certifi

Challenge #2: I needed to know where certifi’s default trust store was located, which I discovered after reading the project github page

python
import certifi
certifi.where()

In my case the location was ‘/usr/lib/python2.7/site-packages/certifi/cacert.pem’. I then symlinked my system trust to that location (backing up existing trust first)

sudo mv /usr/lib/python2.7/site-packages/certifi/cacert.pem /usr/lib/python2.7/site-packages/certifi/cacert.pem.old
sudo ln -s /etc/pki/tls/cert.pem /usr/lib/python2.7/site-packages/certifi/cacert.pem

Et voila! No more trust issues.

Ansible Tower

Note: If you’re running Ansible Tower, you have to work with their own bundled version of python instead of the system version. For version 3.2 it was located here:

/var/lib/awx/venv/ansible/lib/python2.7/site-packages/requests/cacert.pem

I fixed it by doing this:

sudo mv /var/lib/awx/venv/ansible/lib/python2.7/site-packages/requests/cacert.pem /var/lib/awx/venv/ansible/lib/python2.7/site-packages/requests/cacert.pem.old
sudo ln -s /etc/pki/tls/cert.pem /var/lib/awx/venv/ansible/lib/python2.7/site-packages/requests/cacert.pem

This resolved the trust issues.