centos

If you see your Postfix reporting:

Jun 4 10:45:35 host postfix/smtpd[13609]: warning: xsasl_cyrus_server_get_mechanism_list: no applicable SASL mechanisms
Jun 4 10:45:35 host postfix/smtpd[13609]: fatal: no SASL authentication mechanisms

If the Named service goes down we check its status with systemctl status named or journalctl -xe, however sometimes both commands do not contain any indication of specific zone causing the error:

To list all current sessions:

loginctl list-sessions

To investigate details of particular session run:

loginctl show-session [session_id]

The sessions files are located in /run/systemd/sessions on Fedora-based systems and in /run/systemd/sessions on Debian-based systems.

If sessions fill up the /run directory for 100% then per recommendation on
https://www.centos.org/forums/viewtopic.php?f=48&t=65472:

Sometimes we need to override large structure of directories and subdirectories with newer files.

There are two ways of copying all the files in one directory including subdirectories and hidden files to another directory:

cd /orig/dir
tar cvf - . | (cd /dest/dir; tar xvf -)

which tars up the current directory to stdout then pipes it to a subshell that first cd's to the destination directory before untarring stdin.

The second way of doing this is using cp:

yes | cp -rT /orig/dir /dest/dir 2> /dev/null

Enable the epel repository and run:

yum install python-pip to get:

yum install python-pip
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirror.nexcess.net
* epel: mirror.sfo12.us.leaseweb.net
* extras: centos.sonn.com
* updates: centos.sonn.com
Resolving Dependencies
--> Running transaction check
---> Package python-pip.noarch 0:7.1.0-1.el7 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

The easiest way to restore the old way Kernel/modules/udev rename your ethernet interfaces is supplying these kernel parameters to Fedora 19:

net.ifnames=0
biosdevname=0


To do so follow this steps:

1. Edit /etc/default/grub
2. At the end of GRUB_CMDLINE_LINUX line append "net.ifnames=0 biosdevname=0"
3. Save the file
4. Type "grub2-mkconfig -o /boot/grub2/grub.cfg"
5. Type "reboot"

If you see the “Disk contains BIOS metadata, but is not part of any recognized BIOS RAID sets. Ignoring disk sda” error message during OS installation, then you need to remove the raid metadata the “classic” way:

dmraid -r -E /dev/sda
Do you really want to erase "pdc" ondisk metadata on /dev/sda ? [y/n] :
y


Intrusions can take place from both authorized (insiders) and unauthorized (outsiders) users. My personal experience shows that unhappy user can damage the system, especially when they have a shell access. Some users are little smart and removes history file (such as ~/.bash_history) but you can monitor all user executed commands.It is recommended that you log user activity using process accounting. Process accounting allows you to view every command executed by a user including CPU and memory time.