30 Oct 2018 Email notification on SSH login using PAM
There are cases where you are interested in getting a email message on every successful login through SSH. This could have been solved by adding a simple line in .bash_profile for every user, but this solution does not catch all SSH logins. The preferred way of doing it is by using PAM and a custom email notify script.
Add the following line to the bottom of file /etc/pam.d/sshd
session optional pam_exec.so seteuid /usr/local/bin/login-notify.sh
This is the contents of /usr/local/bin/login-notify.sh
#!/bin/sh
# Change these two lines:
sender="root@example.com"
recepient="root"
if [ "$PAM_TYPE" != "close_session" ]; then
host="`hostname`"
subject="SSH Login: $PAM_USER from $PAM_RHOST on $host"
# Message to send, e.g. the current environment variables.
message="`env`"
echo "$message" | mailx -r "$sender" -s "$subject" "$recepient"
fi
Make the script executable
# chmod 0700 /usr/local/bin/login-notify.sh
This is the email message you receive the next time you or someone else log in using SSH
SSH Login: username from hostname-remote.user.com on target-host.example.com
XDG_SESSION_ID=775
SELINUX_ROLE_REQUESTED=
PAM_SERVICE=sshd
SELINUX_USE_CURRENT_RANGE=
PAM_RHOST=hostname-remote.user.com
PAM_USER=username
PWD=/
SELINUX_LEVEL_REQUESTED=
SHLVL=1
PAM_TYPE=open_session
PAM_TTY=ssh
XDG_RUNTIME_DIR=/run/user/9000
_=/usr/bin/env
This has been tested on CentOS 7 and Ubuntu 18.04, but I guess most recent distributions supports this.
DATA PRIVACY
Sending emails on login may conflict with data privacy on multiuser systems. This can be circumvented by just sending emails for specific users or root (if at all accessible via SSH). I might cover that in a later post.
Tags: email, notification, pam, ssh
Posted by Hans-Henry Jakobsen
18 Sep 2018 Reinstall grub using Live-CDROM
After a failed upgrade to Ubuntu 14.04 the server complains about missing disk error. The solution was to reinstall grub and reboot. The procedure is loosely described here.
Boot your Ubuntu server using av Live CDROM you have downloaded from Ubuntu. Choose to Test Ubuntu since installation is not the desired option at this time.
Open a terminal window and become root using the sudo command and make the LVM disks available
# lvm vgscan -v
# vgchange -a y vgdisk-for-root-partition
# mkdir /mnt/rootMount
# mount /dev/vgdisk-for-root-partition/root /mnt/root
Create a chroot environment where you can run the grub-install command
# mount –bind /dev /mnt/root/bind
# mount –bind /proc /mnt/root/proc
# mount /boot /mnt/root/boot
# chroot /mnt/root /bin/bash
# grub-install –root /dev/sda
Always make sure you are working on the right disk before using the grub-install command since it overwrites the boot loader.
Reboot the server when the grub-install command has been successfully run. The server should now be rebooting and working again as it used to.
Tags: chroot, grub-install, lvm, mount, vgchange
Posted by Hans-Henry Jakobsen
17 Jul 2018 Install HAProxy 1.8 on CentOS 7
This is just a short write-up on installing HAProxy version 1.8 on CentOS 7 using Software Collections. HAProxy is an application layer (Layer 7) load balancing and high availability solution that you can use to implement a reverse proxy for HTTP and TCP-based Internet services. I am using it to expose my webservices through a reverse proxy.
If default HAProxy version 1.5 is installed then it should be removed because it is blocking the new version we are going to install.
# yum remove haproxy ... warning: /etc/haproxy/haproxy.cfg saved as /etc/haproxy/haproxy.cfg.rpmsave ...
This warning indicates that your old HAProxy config file is renamed. This is useful to know if you are planning to use the same file in HAProxy version 1.8.
Install the Software Collections (SCL) repository to get access to the new HAProxy version
# yum install centos-release-scl
Update your repositories and accept the new repository.
Installing HAProxy 1.8
# yum install rh-haproxy18-haproxy rh-haproxy18-haproxy-syspaths
The rh-haproxy18-haproxy-syspaths package is a system-wide wrapper for the rh-haproxy18-haproxy package and allows us to run HAProxy 1.8 as a service. This package conflicts with the HAProxy and cannot be installed on one system.
If we now look in /etc/haproxy/haproxy.cfg we will see that the config file is a symling to the new package
# ls -l /etc/haproxy/ lrwxrwxrwx. 1 root root 44 Jul 17 18:19 haproxy.cfg -> /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg
If you had HAProxy 1.5 installed previously and would like to continue using the config file, copy it to the new location. First we preserve the original HAProxy 1.8 config file by renaming it or just copy the rules that you need from the old config.
# mv /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg.original # cp /etc/haproxy/haproxy.cfg.rpmsave /etc/opt/rh/rh-haproxy18/haproxy/haproxy.cfg
We are now ready to start HAProxy 1.8 with our old config file
# systemctl start rh-haproxy18-haproxy # systemctl status rh-haproxy18-haproxy
If we would like to have the new HAProxy version to auto-start on reboot
# systemctl enable rh-haproxy18-haproxy
Done.
Installing HAProxy 1.8 on RedHat 7 is similar, except you use subscription-manager and add the software collections repository.
Tags: CentOS, haproxy, scl, software_collections
Posted by Hans-Henry Jakobsen
02 Mar 2018 Configure VLAN on top of network team using nmcli / NetworkManager
This post is almost similar as the previous where I created a team with two network nics as members using NetworkManager nmcli from a console. This time I have added a VLAN on top of my LACP network team with two member nics.
First we need to install the teamd package if it is not already installed.
# yum install teamd
Using the console command nmcli and NetworkManager and a json-config file with the default config for the team, filename team-master-conf.json:
{
"runner": {
"active": true,
"fast_rate": true,
"name": "lacp",
"tx_hash": [ "eth", "ipv4" ]
},
"tx_balancer": { "name": "basic" },
"link_watch": { "name": "ethtool" }
}
# nmcli con add type team con-name team0 ifname team0 config team-master-conf.json # nmcli con add type team-slave con-name team0-em1 ifname em1 master team0 # nmcli con add type team-slave con-name team0-em2 ifname em2 master team0
I have not added an IP-address to the new team since I will add that on the VLAN interface.
Check the status of the team
# nmcli con status NAME UUID TYPE DEVICE team0 7f0c0038-b8c1-45bb-a286-501d02304700 team team0 team0-em1 0394e2ae-6610-4997-92db-775876866d0d 802-3-ethernet em1 team0-em2 7050d641-83bb-497a-ae23-6af029386117 802-3-ethernet em2
Check the state of the team
# teamdctl team0 state
setup:
runner: lacp
ports:
em1
link watches:
link summary: up
instance[link_watch_0]:
name: ethtool
link: up
down count: 1
runner:
aggregator ID: 12, Selected
selected: yes
state: current
em2
link watches:
link summary: up
instance[link_watch_0]:
name: ethtool
link: up
down count: 0
runner:
aggregator ID: 12, Selected
selected: yes
state: current
runner:
active: yes
fast rate: yes
Add a VLAN to the network team
# nmcli con add type vlan con-name team0-vlan12 dev team0 id 12 ip4 10.1.0.20/24 gw4 10.1.0.1
The new config looks like this
# nmcli con s | grep team team0 7f0c0038-b8c1-45bb-a286-501d02304700 team team0 team0-vlan12 d5de0d83-d490-4535-915c-4cbdcf39830b vlan team0.12 team0-em1 0394e2ae-6610-4997-92db-775876866d0d 802-3-ethernet em1 team0-em2 7050d641-83bb-497a-ae23-6af029386117 802-3-ethernet em2
This config is confirmed working on RHEL 7.4 and Centos.
I assume the switch is configured as needed before starting this config on the server.
Tags: CentOS, lacp, nmcli, RedHat, rhel7, teamd, teamdctl, vlan
Posted by Hans-Henry Jakobsen
