Category Archives: CLI

Fix icedtea Cannot grant permissions to unsigned jars error

I banged my head on a wall for a while before I finally found a fix to this one. OpenJDK8 has new security features that break compatibility with the IPMI interfaces of my older servers. The problem in my case stemmed from the fact that the java applet is signed, just with an algorhythm that JDK8 blacklists. So, I had to remove MD5 from the blacklisted algorhythms to get this to work. Thanks to this site for guidance on how to do this.

Per that site, this is what I did to fix the issue:

Find the java.security file. In my case it is located in /usr/lib/jvm/java-8-openjdk-amd64/jre/lib/security/java.security

Then find the row:

1
jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024

Comment it out, copy it, delete the MD5 string.

1
2
#jdk.jar.disabledAlgorithms=MD2, MD5, RSA keySize < 1024
jdk.jar.disabledAlgorithms=MD2, RSA keySize < 1024

MariaDB with Active Directory authentication via PAM module

I needed to get mariadb authenticating users via Active Directory at work. Configuration was confusing until I stumbled across this article saying you can just tie into the system’s PAM configuration., which in my case is already configured for AD authentication. Awesome!

First, enable PAM plugin and restart mariadb:

/etc/my.cnf, anywhere in the mysqld section

plugin-load=auth_pam.so

Restart mariadb:

sudo systemctl restart mariadb

Next, configure a PAM file to interface with mariadb:

sudo vi /etc/pam.d/mysql
auth include system-auth 
account required pam_nologin.so 
account include system-auth 
password include system-auth 
session optional pam_keyinit.so force revoke 
session include system-auth 
session required pam_loginuid.so

Create catch all user in MariaDB and configure to use your PAM configuration:

CREATE USER ''@'%' IDENTIFIED VIA pam USING 'mysql';

Lastly, grant permissions in mariadb being sure to specify pam as the mechanism:

GRANT ALL PRIVILEGES on <database>.* to '<user>'@'<host>' IDENTIFIED VIA pam;

Profit.

Rename files to reflect modified time while preserving extension

I’m undergoing a big project of scanning old family scrapbooks. I have two scanners involved, each with their own naming scheme, dumping files of various types (pdf, jpg) into the same folder. I need to have an accurate chronological view of when things were scanned (nothing was scanned at the exact same moment.) At this point the only way to get this information is to sort all the files by modified time,  but no other programs but a file manager look at files this way. I needed a way to rename all the files to reflect their modified time.

I found a couple different ways to do this, but settled on a bash for loop utilizing the stat, sed, and mv commands.

Challenge 1

Capture the extension of the files.

Using sed:

ls <filename> | sed 's/.*\(\..*\)$/\1/'

Challenge 2

Obtain the modified time of your file in an acceptable format. I do this using the stat command.

stat -c %y <filename>

%y is the best option here – it leaves no room for ambiguity. You could also choose %Y so the filenames aren’t so large and don’t contain colons (some systems struggle with this.) The downside do this is you only have to-the-second precision. In my case I had a few files that had the same epoch timestamp, which caused problems. More on how to format this can be found here and here.

Stringing it all together

I wrapped it all up in a bash for loop with appropriate variables. This was my final command, which I ran inside the directory I wanted to modify:

for file in *; do name=$(stat -c %y "$file"); ext=$(echo "$file" | sed 's/.*\(\..*\)$/\1/'); mv -n "$file" "$name$ext"; done

The for loop goes through each file one at a time and assigns it to the $file variable.  I then create the name variable which uses the stat command to obtain a precise date modified timestamp of the file. The ext variable is derived from the filename but only keeps the extension (using sed.) The last step uses mv -n (no clobber mode – don’t overwrite anything) to rename the original file to its date modified timestamp. The result: a directory where each file is named precisely when it was modified – a true chronology of what was scanned irrespective of file extension or which scanner created the file. Success.

Make Java run on privileged ports in CentOS 7

I recently gnashed my teeth at trying to get java to directly bind to port 443 instead of using nginx to proxy to a java application I had to use. I was surprised at the complication of finding the solution, but I eventually did thanks to the following sites:

https://superuser.com/questions/710253/allow-non-root-process-to-bind-to-port-80-and-443/892391

https://github.com/kaitoy/pcap4j/issues/63

First, determine the full path of your current java install:

sudo update-alternatives --config java

In my CentOS 7 install, the java binary was located here:

/usr/lib/jvm/java-1.8.0-openjdk-1.8.0.151-1.b12.el7_4.x86_64/jre/bin/java

Next, use setcap to configure java to be able to bind to port 443:

sudo setcap CAP_NET_BIND_SERVICE=+eip /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.151-1.b12.el7_4.x86_64/jre/bin/java

Now, test to make sure java works:

java -version

java: error while loading shared libraries: libjli.so: cannot open shared object file: No such file or directory

The above error means that after setting setcap, it breaks how java looks for its library to run. To fix this, we need to symlink the library it’s looking for into /usr/lib, then run ldconfig

sudo ln -s /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.151-1.b12.el7_4.x86_64/jre/lib/amd64/jli/libjli.so /usr/lib/
sudo ldconfig

Now test Java again:

java -version

It took longer than I like to admit to get this working, but it it does indeed work this way.

gvfs-mount doesn’t use kerberos ticket fix

I had a very frustrating issue when I switched my work desktop from Linux Mint to CentOS 7. My network drives no longer would mount using a kerberos ticket. Before, when I would initialize a kerberos ticket I could mount network shares without any kind of username or password prompt:

kinit
gvfs-mount smb://server/share

With CentOS 7, though, the above process would produce a username and password prompt. After much searching I came across this forum that contained the answer: append your fully qualified domain name to the server. Now the process is like this:

kinit
gvfs-mount smb://server.full.fqdn.name/share

and it worked!

Fix no bluetooth devices found in Linux Mint

I had a peculiar issue today where I suddenly lost the ability to see any bluetooth devices on my Linux Mint 18.2 desktop utilizing a Plugable USB Bluetooth adapter.

The fix involved checking kernel messages for anything insightful. In my case this is what led me to the solution:

[ 608.988353] Bluetooth: hci0: BCM: Patch brcm/BCM20702A1-0a5c-21e8.hcd not found
[ 609.156320] Bluetooth: hci0: BCM: chip id 63
[ 609.172330] Bluetooth: hci0: LPP-3389-WIN
[ 609.173313] Bluetooth: hci0: BCM20702A1 (001.002.014) build 1764
[ 609.173347] bluetooth hci0: Direct firmware load for brcm/BCM20702A1-0a5c-21e8.hcd failed with error -2

After some googling I finally came across the solution here. The fix is to download the firmware for your bluetooth adapter and place it in the place the bluetooth kernel module expects it to be in, then to reload the bluetooth kernel module.

sudo mkdir -p /lib/firmware/brcm
sudo wget https://s3.amazonaws.com/plugable/bin/fw-0a5c_21e8.hcd -O /lib/firmware/brcm/BCM20702A1-0a5c-21e8.hcd
sudo rmmod btusb bnep bluetooth btrtl btintel bnep btbcm
sudo modprobe btusb bnep bluetooth btrtl btintel bnep btbcm

That did the trick! You can also reboot your machine instead of removing / re-loading the kernel modules and it will accomplish the same thing.

Fix WordPress “Sorry, you are not allowed to access this page.”

I recently came across an issue with my WordPress installation. It’s situated behind a load balancer where SSL is terminated. The load balancer takes HTTPS traffic, then forwards it as HTTP on port 80 to the wordpress server.

I was running issues with a redirect loop after installing wordpress. The solution was to add this bit of code to wp-config.php:

define('FORCE_SSL_ADMIN', true);
if ($_SERVER['HTTP_X_FORWARDED_PROTO'] == 'https')
 $_SERVER['HTTPS']='on';

This solves the redirect loop issue but then I ran into a different problem. When I tried to sign into wp-admin I would get this message:

Sorry, you are not allowed to access this page.

After much digging I found this post which emphasizes that you must place that code BEFORE anything else in wp-config.php (except for the beginning PHP tag.) Success!

Fix no sound in Wine

Lately I’ve been doing 100% of my gaming in Linux. The latest versions of wine in Arch Linux have been fantastic (for the most part.) I recently installed a game called Gauntlet (a windows-only steam game.) For some reason I had no sound. Sound worked fine in other Wine games, just not this one.

After much digging I found this post on the Arch Linux forums which fixed my issue. The issue was not having the proper 32bit sound libraries installed. The fix was as simple as:

sudo pacman -Sy lib32-alsa-plugins lib32-libpulse lib32-openal

Success!

Backup your systems with urBackup

In addition to my ZFS snapshots I decided to implement a secondary backup system. I decided to land on urbackup for ease of use and, more importantly, it was easier to set up.

Server Install

Assuming a Cent-based system:

cd /etc/yum.repos.d/
sudo wget http://download.opensuse.org/repositories/home:uroni/CentOS_7/home:uroni.repo
sudo yum -y install urbackup-server
sudo systemctl enable urbackup-server
sudo systemctl start urbackup-server

Open up necessary ports for the server:

sudo firewall-cmd --add-port=55413-55415/tcp --permanent
sudo systemctl reload firewalld

By default urbackup listens on port 55414 for connections. You can change this to port 80 and/or 443 for HTTPS by installing nginx and having it proxy the connections for you.

sudo yum -y install nginx
sudo systemctl enable nginx
sudo setsebool -P httpd_can_network_connect 1 #if you're using selinux

Copy the following into /etc/nginx/conf.d/urbackup.conf (make sure to change server_name to suit your needs)

server {
        server_name backup;

        location / {
                proxy_pass http://localhost:55414/;
        }
}

Then start nginx:

sudo systemctl start nginx

You should then be able to access the urbackup console by navigating to the IP / hostname of your backup server in a browser.

Client Install:

Urbackup can use a snapshot system known as dattobd. You should use it if you can in order to get more consistent backups, otherwise urbackup will simply copy files from the host which isn’t always desirable (databases, for example)

Install dattobd (optional):

sudo yum -y update
# reboot if your kernel ends up being updated
sudo yum -y localinstall https://cpkg.datto.com/datto-rpm/repoconfig/datto-el-rpm-release-$(rpm -E %rhel)-latest.noarch.rpm
sudo yum -y install dkms-dattobd dattobd-utils

Install urbackup client:

TF=`mktemp` && wget "https://hndl.urbackup.org/Client/2.1.15/UrBackup%20Client%20Linux%202.1.15.sh" -O $TF && sudo sh $TF; rm $TF
#Select dattobd when prompted if desired

Configure Firewall:

sudo firewall-cmd --add-port=35621-35623/tcp --permanent
sudo systemctl reload firewalld

Once a client is installed, assuming they’re on the same network as the backup server, they will automatically add themselves and begin backing up. If they don’t show up it’s usually a firewall issue.

Restore

Restoration of individual files is easily done through the web console. If you have a windows system, restoring from an image backup is also easy.

Linux hosts

Recovery is trickier if you want to restore a Linux system. Install an empty system of same distribution. Give it the same hostname. Install the client as outlined above, then run:

sudo /usr/local/bin/urbackupclientctl restore-start -b last

Troubleshooting

If for some reason the client not showing up after removing it from the GUI: Uninstall & re-install client software

sudo /usr/local/sbin/uninstall_urbackupclient
TF=`mktemp` && wget "https://hndl.urbackup.org/Client/2.1.15/UrBackup%20Client%20Linux%202.1.15.sh" -O $TF && sudo sh $TF; rm $TF