Tag Archives: linux

Fix Proxmox swapping issue

I recently had an issue with one of my Proxmox hosts where it would max out all swap and slow down to a crawl despite having plenty of physical memory free. After digging and tweaking, I found this post which directed to set the kernel swappiness setting to 0. More reading suggested I should set it to 1, which is what I did.

Append to /etc/sysctl.conf:

#Fix excessive swap usage
vm.swappiness = 1 

Apply settings with:

sysctl --system

This did the trick for me.

Rasbperry Pi as a dashboard computer

Here are my raw, unpolished notes on how I set up a raspberry pi to serve as a dashboard display:

Use Raspbian OS

Autostart Chrome in kiosk mode

Eliminate Chrome crash bubble thanks to this post

mkdir -p ~/.config/lxsession/LXDE-pi/
nano ~/.config/lxsession/LXDE-pi/autostart

Add this line:
@chromium-browser --kiosk --app=<URL>

Mouse removal

sudo apt-get install unclutter

in ~/.config/lxsession/LXDE-pi/autostart add

@unclutter -idle 5

Disable screen blank:

in /etc/lightdm/lightdm.conf add

[SeatDefaults]
xserver-command=X -s 0 -dpms

Open up SSH & VNC

Pi / Preferences / Raspberry Pi Configuration: Interfaces tab

SSH: Enable
VNC: Enable

Increase swap file

sudo nano /etc/dphys-swapfile
CONF_SWAPSIZE=2048M

Configure NTP

sudo apt-get install openntpd ntpdate
sudo systemctl enable openntpd
sudo ntpdate <IP of NTP server>

edit /etc/openntpd/ntpd.conf and modify servers lines to fit your NTP server

Disable overscan

Pi / Preferences / Raspberry Pi Configuration: System tab
Overscan: Disable

Recover files from ZFS snapshot of ProxMox VM

I recently needed to restore a specific file from one of my ProxMox VMs that had been deleted. I didn’t want to roll back the entire VM from a previous snapshot – I just wanted a single file from the snapshot. My snapshots are handled via ZFS using FreeNAS.

Since my VM was CentOS 7 it uses XFS, which made things a bit more difficult. I couldn’t find a way to crash-mount a read-only XFS snapshot – it simply resufed to mount, so I had to make everything read/write. Below is the process I used to recover my file:

On the FreeNAS server, find the snapshot you wish to clone:

sudo zfs list -t snapshot -o name -s creation -r DATASET_NAME

Next, clone the snapshot

sudo zfs clone SNAPSHOT_NAME CLONED_SNAPSHOT_NAME

Next, on a Linux box, use SSHFS to mount the snapshot:

mkdir Snapshot
sshfs -o allow_other user@freenas:/mnt/CLONED_SNAPSHOT_NAME Snapshot/

Now create a read/write loopback device following instructions found here:

sudo -i #easy lazy way to get past permissions issues
cd /path/to/Snapshot/folder/created/above
losetup -P -f VM_DISK_FILENAME.raw
losetup 
#Take note of output, it's likely set to /dev/loop0 unless you have other loopbacks

Note if your VM files are not in RAW format, extra steps will need to be taken in order to convert it to RAW format.

Now we have an SSH-mounted loopback device ready for mounting. Things are complicated if your VM uses LVM, which mine does (CentOS 7). Once the loopback device is set, lvscan should see the image’s logical volumes. Make the desired volume active

sudo lvscan
sudo lvchange -ay /dev/VG_NAME/LV_NAME

Now you can mount your volume:

mkdir Restore
mount /dev/VG_NAME/LV_NAME Restore/

Note: for XFS you must have read/write capability on the loopback device for this to work.

When you’re done, do your steps in reverse to unmount the snaspshot:

#Unmount snapshot
umount Restore
#Deactivate LVM
lvchange -an /dev/VG_NAME/LV_NAME
Remove loopback device
losetup -d /dev/loop0 #or whatever the loopback device was
#Unmount SSHfs mount to ZFS server
umount Snapshot

Finally, on the ZFS server, delete the snapshot:

sudo zfs destroy CLONED_SNAPSHOT_NAME

Troubleshooting

When I tried to mount the LVM partition at this point I got this error message:

mount: /dev/mapper/centos_plexlocal-root: can't read superblock

It ended up being because I was accidentally creating a read-only loopback device. I destroy the loopback device and re-created with write support and all was well.

Find video files in bash

I wanted a quick way to search my files for video types. I found here a quick snippet on how to do so. I augmented it after finding out how to remove some info and make it case insensitive. Here is the result:

find FULL_FOLDER_PATH -type f | grep -E "\.webm$|\.flv$|\.vob$|\.ogg$|\.ogv$|\.drc$|\.gifv$|\.mng$|\.avi$|\.mov$|\.qt$|\.wmv$|\.yuv$|\.rm$|\.rmvb$|/.asf$|\.amv$|\.mp4$|\.m4v$|\.mp*$|\.m?v$|\.svi$|\.3gp$|\.flv$|\.f4v$" -iname|sed 's/^.*://g'|sort

Upgrading AWX

AWX is the open source version of Ansible Tower. It’s a powerful tool, but unfortunately AWX has no in place upgrade capability. If you want to upgrade your AWX to the latest version it takes a bit of trickery (the easy way out being just to pay for Ansible Tower.)

Essentially to upgrade AWX you need to spin up a completely new instance and then migrate your data over to it. Fortunately there is a script out there that makes doing this a bit easier.

Below are my notes for how I upgraded my instance of AWX from version 1.0.6 to 2.1.0.

Create temporary AWX migration server

Spin up new server with ansible installed, then clone AWX

git clone https://github.com/ansible/awx.git 
cd awx 
git clone https://github.com/ansible/awx-logos.git

Modify AWX install to expose 5432 externally:

edit installer/roles/local_docker/tasks/standalone.yml and add

    ports:
      - "5432:5432" 

right above the when: pg_hostname is not defined or pg_hostname == '' line. Complete stanza looks like this:

- name: Activate postgres container
  docker_container:
    name: postgres
    state: started
    restart_policy: unless-stopped
    image: "{{ postgresql_image }}"
    volumes:
      - "{{ postgres_data_dir }}:/var/lib/postgresql/data:Z"
    env:
      POSTGRES_USER: "{{ pg_username }}"
      POSTGRES_PASSWORD: "{{ pg_password }}"
      POSTGRES_DB: "{{ pg_database }}"
      PGDATA: "/var/lib/postgresql/data/pgdata"
    ports:
      - "5432:5432"
  when: pg_hostname is not defined or pg_hostname == ''
  register: postgres_container_activate

Make sure you have port 5432 open on your host-based firewall.

Install AWX on the new host. Verify you can log into the empty instance and that it’s the version you want to upgrade to.

Prepare original AWX server to send

Kill the AWX postgres container on the source machine, and re-run awx installer after modifying it to expose its postgres port as described above.

Install tower-cli (this can be on either source or destination servers)

sudo pip install ansible-tower-cli

Configure tower-cli

tower-cli config username SRC_AWX_USERNAME
towercli config password SRC_AWX_PASSWORD
towercli config host SRC_AWX_HOST

Make sure to use full ansible URL as accessed from a browser for both source and destination

Install awx-migrate:

git clone https://github.com/autops/awx-migrate.git

Update awx-migrate/awx-migrate-wrapper with correct source and destination info

Run awx-migrate-wrapper. It will generate json files with your configuration.

Migrate database to temporary server

Modify tower-cli config, set host, username and password to that of the destination AWX instance

tower-cli config username DEST_AWX_USERNAME
towercli config password DEST_AWX_PASSWORD
towercli config host: DEST_AWX_HOST

Send JSON info to destination:

tower-cli send awx-data.json

You will now have a fresh new, updated AWX instance working, with imported database, on the destination host. Confirm you can log into it with the admin account you set it up with.

Prepare original AWX server to receive

Now, on the source, remove  the old AWX docker containers:

sudo docker rm -f postgres awx_task awx_web memcached rabbitmq

Move / delete the database folder the postgres docker container was using (as defined in awx installer inventory) in my case:

/var/lib/awx
/var/db/pgsqldocker

Remove and re-install AWX folder with a fresh git checkout

rm -rf awx
git clone https://github.com/ansible/awx.git
cd awx
git clone https://github.com/ansible/awx-logos.git

Re-run the AWX installer to re-create a blank database on the source host, modify the new awx/installer/inventory as needed. Also modify installer/roles/local_docker/tasks/standalone.yml as outlined above.

cd awx/installer
sudo ansible-playbook -i inventory install.yml

Migrate from temporary AWX server back to source AWX server

Once a new, empty version of awx is running on the source host,  start the awx-migrate process in reverse to migrate the database on the destination instance back to the source. Modify awx-migrate-wrapper and tower-cli to switch src and destination (the destination has become the source and the source has become the destination)

Use awx-migrate-wrapper to generate  new ansible version json files (don’t confuse them with the old json files – best to delete / move all json files before running awx-migrate-wrapper)

Modify tower-cli to point to original AWX URL

Run tower-cli send awx-data.json

Once completed, log in as the admin account. Input LDAP BIND password under settings, then delete any imported LDAP users.

Cleanup

You may want to remove the exposed postgres database ports. Simply undo the changes you made in awx/installer/roles/local_docker/tasks/standalone.yml to remove the Ports part of the first play, then remove your postgres container and re-install AWX with install.yml

Also remember to delete the JSON files generated with awx-migrate as they contain all your credentials in plaintext.

Success.

 

Configure ACLs in Linux

I came across a need to make files in a folder inherit certain permissions no matter who creates them. Thanks to Stack Overflow for help in figuring this out.
You first set a sticky bit for the parent folder, then use the setfacl command to set the ACL:
chmod g+s -R <folder>
setfacl -d -m "g:<group name>:<permissions>" -R <directory>
Example:
Grants all members of group testgrouprw read,write, and directory permissions to /var/www/html/wordpress:
setfacl -d -m "g:testgrouprw:rwX" -R /var/www/html/wordpress/
Sources:

Rotate videos for WordPress using ffmpeg

WordPress has an extremely annoying issue with reading EXIF data when posting photos and videos. There is a plugin to fix rotated pictures, but I couldn’t find one for rotated videos. If you happen to upload a video from your phone that was shot in portait orientation, it will likely upload to wordpress in landscape orientation (sideways.) Very annoying.

My fix to this is to re-encode the video so it is at the proper orientation before uploading to wordpress. Thanks to this site for the information – ffmpeg does this automatically for you. So the syntax is simple:

ffmpeg -i SOURCE_VIDEO_FILENAME -c:a copy FIXED_VIDEO_FILENAME.mp4

Success.

Active Directory / LDAP integration with WordPress

I struggled for a while to get WordPress to use Active Directory credentials on CentOS 7. Below is how I finally got it to work.

First, install necessary packages:

sudo yum -y install openldap-clients php-ldap

If you use self-signed certificate for ldaps, you’ll need to modify /etc/openldap/ldap.conf

HOST <HOSTNAME_OF_LDAP_SERVER>
PORT 636
TLS_CACERT <PATH_TO_CA_CERT>
TLS_REQCERT demand

With the above settings you can test your ldap string with ldapsearch

ldapsearch -x -D "<BIND USERNAME>" -b "<BASE_DN>" -H ldaps://<LDAP_SERVER_HOSTNAME> -W sAMAccountName=<USER_TO_QUERY>

Once ldapsearch works properly, install your AD integration plugin.  I use AuthLDAP by Andreas Heigl

I struggled with which LDAP strings and filters to use. This is what finally got everything working with our Active Directory environment:

LDAP URIldaps://<BIND_USERNAME>:<BIND_PASSWORD>@<AD_SERVER_ADDRESS>:636/<BASE DN>

Filter(sAMAccountName=%s)

Name-AttributegivenName

User-ID Attribute: sAMAccountName

Second Name Attributesn

Group-Attribute:memberOf

Group-Separator:  _

Group-Filter: (&(objectClass=user)(sAMAccountName=%s)(memberOf=*))

Role – group mapping

I had to change Group-Separator to _ above, because in Role – group mapping for active directory, you must put the FQDN, which includes commas. Put an underscore separated list of FQDNS for each of these fields you want.

Using expect with the Ansible shell module

In one of my ansible playbooks I need to obtain a file from a Windows share. I can’t find a module that handles this so I’m using the shell module to call the smbclient command to do what I need. The problem with this solution is that smbclient prompts for a password (and I don’t want to supply it on the command itself for security reasons.)

I tried using ansible’s built-in expect module, but frustratingly it only works on systems that have pexpect >= 3.3  , which CentOS 7 & Ubuntu 14.04 do not have.

My solution to this is to install the expect command on the host, and then use the ansible shell module to call it, following the example given in Ansible’s shell module page

Part of the process in my playbook is registering stdout from that command for later use. I then ran into a problem where I would run smbclient -c “ls <filename>” but ansible would register nothing. After some digging I found I also need to include the interact command after sending the password. Without it, anything after sending the password is not registered to stdout. Thanks to rostyslav-fridman on Stack Overflow for the answer.

My final problem was I was sending a password that had a ] character in it. It was causing this error on run:

missing close-bracket\n while executing\n\"send

I found here (thanks glenn-jackman) it was due to  the fact that the expect syntax uses tcl language, which treats those brackets as special characters. To get around this I had to use an ansible filter, specifically regex_escape()

Lastly I ran into an issue specifically with how I was spawning smbclient. I kept getting this message:

"stderr": "send: spawn id exp4 not open\n while executing\n\"send

It boiled down to single vs double quotes. If I put my -c arguments in single quotes it failed; with double quotes, it worked.

My completed play is below. Finally, success!

- name: Get RSA filename 
  shell: |
    set timeout 300
    spawn smbclient {{standards_location}} -W DOMAIN -U {{username}} -c "ls {{file_location}}*.tar"
    expect "password:"
    send {{ password | regex_escape() }}\r
    interact
    exit 0
  args:
    executable: /usr/bin/expect
  changed_when: false
  no_log: true
  register: RSA_filename_raw