Repairing Fedora grub from chroot

Notes from repairing a Fedora drive.

Mount system in chroot.

If the system is a raid drive and your not able to access it refer to this post.  May just need to install the raid utilities.

For mounting the chroot environment refer to this post

Repairing grub

yum install grub2-efi-*

Install grub.  Change /sda to your drive, may need to specify the efi partition.

grub2-install /dev/sda

If your boot and efi partitions are mounted.

grub2-mkconfig -o /boot/efi/EFI/fedora/grub.cfg

Reboot.

DNF/YUM not working in chroot environment

The reason is probably because the chrooted environment can’t resolve DNS.

Test it with

ping incredigeek.com

If it is not resolving, edit “/etc/resolv.conf” and change/add your nameserver.  Or just replace everything in it with

echo "nameserver 4.2.2.2" > /etc/resolv.conf

It should now be able to resolve and you should be able to use yum, or dnf.

yum update

RAID Volume not accessible in Linux

Typically your RAID volumes will show up as /dev/mdXXX

If it is not, it could be because the device mapper module is not loaded.  Load it by running the following command.

modprobe dm-mod

As a side note you can list the block devices using

dmraid -b

https://bbs.archlinux.org/viewtopic.php?id=42321

If your still having trouble you can try installing mdadm and dmraid

apt-get install -y dmraid mdadm

 

Delete SNMPv3 User on Linux

Don’t know if this is the recommended way to delete a user, but it seems to work.

sudo service snmpd stop

Open up the snmpd.conf file in /var/lib and find the line with the SNMP user and delete the line

sudo vi /var/lib/snmp/snmpd.conf

The above file may be in the following location on RPM based systems.

sudo vi /var/lib/net-snmp/snmpd.conf

Save, exit, and start snmpd

sudo service snmpd start

These steps work for Ubuntu, but should work for any Debain based distro as well as CentOS, Fedora, RedHat etc.

Install dig on Ubuntu, Debian or Kali Linux

install dig
Help options for dig


Dig is a DNS lookup utility.  It is included in most Linux distributions by default, but if it isn’t you can easily install dig with the following command.

The dig utility is apart of the dnsutils package

sudo apt-get install dnsutils -y

After it is installed, we can verify that it is working with

dig -v

For more information on how to use dig, refer to the following link.

https://www.howtogeek.com/663056/how-to-use-the-dig-command-on-linux/

The following is copied and pasted from the dig man page.

NAME
       dig - DNS lookup utility

SYNOPSIS
       dig [@server] [-b address] [-c class] [-f filename] [-k filename] [-m] [-p port#] [-q name]
           [-t type] [-v] [-x addr] [-y [hmac:]name:key] [[-4] | [-6]] [name] [type] [class]
           [queryopt...]

       dig [-h]

       dig [global-queryopt...] [query...]

DESCRIPTION
       dig is a flexible tool for interrogating DNS name servers. It performs DNS lookups and
       displays the answers that are returned from the name server(s) that were queried. Most DNS
       administrators use dig to troubleshoot DNS problems because of its flexibility, ease of use
       and clarity of output. Other lookup tools tend to have less functionality than dig.

       Although dig is normally used with command-line arguments, it also has a batch mode of
       operation for reading lookup requests from a file. A brief summary of its command-line
       arguments and options is printed when the -h option is given. Unlike earlier versions, the
       BIND 9 implementation of dig allows multiple lookups to be issued from the command line.

       Unless it is told to query a specific name server, dig will try each of the servers listed
       in /etc/resolv.conf. If no usable server addresses are found, dig will send the query to the
       local host.

       When no command line arguments or options are given, dig will perform an NS query for "."
       (the root).

       It is possible to set per-user defaults for dig via ${HOME}/.digrc. This file is read and
       any options in it are applied before the command line arguments. The -r option disables this
       feature, for scripts that need predictable behaviour.

       The IN and CH class names overlap with the IN and CH top level domain names. Either use the
       -t and -c options to specify the type and class, use the -q the specify the domain name, or
       use "IN." and "CH." when looking up these top level domains.

SIMPLE USAGE
       A typical invocation of dig looks like:

            dig @server name type

       where:

       server
           is the name or IP address of the name server to query. This can be an IPv4 address in
           dotted-decimal notation or an IPv6 address in colon-delimited notation. When the
           supplied server argument is a hostname, dig resolves that name before querying that name
           server.

           If no server argument is provided, dig consults /etc/resolv.conf; if an address is found
           there, it queries the name server at that address. If either of the -4 or -6 options are
           in use, then only addresses for the corresponding transport will be tried. If no usable
           addresses are found, dig will send the query to the local host. The reply from the name
           server that responds is displayed.

       name
           is the name of the resource record that is to be looked up.

       type
           indicates what type of query is required — ANY, A, MX, SIG, etc.  type can be any valid
           query type. If no type argument is supplied, dig will perform a lookup for an A record.


					

Add multiple IP bindings to Mikrotik Hotspot – Bash Script

Copy and paste the following into a file named mtbypass.sh and then “chmod +x mtbypass.sh”  Or download from this direct link.  Be sure to change the username and password

#!bin/bash
filelist="bypasslist.txt"
username="admin"
password="password!"
ip="$1"

for i in `cat ${filelist}`
do
address=`echo $i | cut -d= -f1`
mac=`echo $i | cut -d= -f2`
sshpass -p ${password} ssh ${username}@${ip} "ip hotspot ip-binding add address=${address} mac-address=${mac} type=bypassed"
done

Now create a file named bypasslist.txt and put all the addresses you want bypassed.  You’ll need the Mac Address and the IP Address.

Example file

192.168.88.2=4C:5E:0C:B8:4E:01
192.168.88.3=3E:AA:A1:2D:8B:2C
192.168.88.5=DE:D1:39:65:91:4E

Usage of script is

./mtbypass.sh MikrotikIP

Example:

./mtbypass.sh 192.168.88.1

LibreNMS Error: Missing dependencies! Run the following command to fix:

Received this error while trying to access LibreNMS in web browser.

Error: Missing dependencies! Run the following command to fix:

./scripts/composer_wrapper.php install –no-dev

 

Tried sshing into the LibreNMS server and running the script, but that didn’t fix the issue.

Ran ./validate.php and it came up with the some of the following errors.

[FAIL] Missing PHP extension: mbstring
[FIX] Please install mbstring
[FAIL] The poller (localhost.localdomain) has not completed within the last 5 minutes, check the cron job.
[WARN] Your install is over 24 hours out of date, last update: Thu, 7 May 2018 19:18:35 +0000
[FIX] Make sure your daily.sh cron is running and run ./daily.sh by hand to see if there are any errors.

Installed mbstring.  You may need to change the number if yum is complaining about package conflicts.  Use “yum search mbstring” to show all the versions available.

yum install php71w-mbstring

Ran ./validate.php again and it wanted this script run

./scripts/composer_wrapper.php install --no-dev

Restart Apache

systemctl restart httpd