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Install Jekyll on Amazon Linux 2

Here’s the script to install Jekyll on Amazon Linux 2.

#!/bin/bash
sudo hostnamectl set-hostname jekyll
sudo yum update -y
sudo amazon-linux-extras install ruby2.4 -y
sudo yum install ruby ruby-devel -y
sudo yum groupinstall "Development Tools" -y
sudo gem install bundler 
sudo gem install rdoc
sudo gem update --system
sudo gem install jekyll
jekyll new myblog

To start the Jekyll server.

cd mysite
jekyll build
jekyll serve --host 0.0.0.0

Open your browser and point it to the external IP of your instance on port 4000. 

http://xxx.xxx.xxx.xxx:4000

You may to edit your security group to allow ingress 4000 from 0.0.0.0/0.

Checking Yum Transaction Logs

Check if package is on system.

rpm -q httpd
httpd-2.4.6-97.el7.centos.x86_64

Check the history logs.

yum history list
Loaded plugins: fastestmirror
ID     | Login user               | Date and time    | Action(s)      | Altered
-------------------------------------------------------------------------------
   115 | System <unset>           | 2021-02-01 03:40 | Update         |    1
   114 | System <unset>           | 2021-02-01 02:03 | I, U           |   10
   113 | System <unset>           | 2021-01-29 19:54 | Update         |    1
   112 | System <unset>           | 2021-01-21 14:41 | Update         |    1

Check detail transaction id.

yum history info 114 | grep python 
    Updated python-perf-3.10.0-1160.6.1.el7.x86_64          @updates
    Updated python-sss-1.16.5-10.el7_9.5.x86_64             @cah-cloud-centos7-updates
    Updated python-sssdconfig-1.16.5-10.el7_9.5.noarch      @cah-cloud-centos7-updates

It looks like python was updated in transaction id #114.

Restart RPC GSSD Service

If a Linux user is having an access problem with a NFS share, and particularly with key expiration, then check if the RPC GSSD service is up and running. NFS clients uses the RPCSEC_GSS protocol to establish security credentials with a NFS server using Kerberos authentication.

Here’s an example of a key expire error due to a NFS client not authenticated properly.

df -h
df: '/data/dir1': Key has expired
df: '/data/dir2': Key has expired
df: '/data/dir3': Key has expired

Check if RPC GSSD service is healthy. Restart the service if there are credential errors.

service rpc-gssd status

Here’s one with an authentication issue.

[root@server ~]# service rpc-gssd status
Redirecting to /bin/systemctl status rpc-gssd.service
● rpc-gssd.service - RPC security service for NFS client and server
   Loaded: loaded (/usr/lib/systemd/system/rpc-gssd.service; static; vendor preset: disabled)
   Active: active (running) since Sun 2021-01-31 03:16:43 CST; 2h 14min ago
 Main PID: 710 (rpc.gssd)
   Memory: 1.6M
   CGroup: /system.slice/rpc-gssd.service
           └─710 /usr/sbin/rpc.gssd
 
Jan 31 03:17:10 server.domain.com rpc.gssd[710]: ERROR: gssd_refresh_krb5_machine_credential: no usable keytab entry found
Jan 31 03:17:10 server.domain.com rpc.gssd[710]: ERROR: No credentials found for connection to server nas.domain.com
Jan 31 03:17:10 server.domain.com rpc.gssd[710]: ERROR: gssd_refresh_krb5_machine_credential: no usable keytab entry found
Jan 31 03:17:10 server.domain.com rpc.gssd[710]: ERROR: No credentials found for connection to server nas.domain.com

Restart the service.

service rpc-gssd stop
service rpc-gssd start

Here’s a service that’s healthy.

[root@server ~]# service rpc-gssd status
Redirecting to /bin/systemctl status rpc-gssd.service
● rpc-gssd.service - RPC security service for NFS client and server
   Loaded: loaded (/usr/lib/systemd/system/rpc-gssd.service; static; vendor preset: disabled)
   Active: active (running) since Sun 2021-01-31 05:33:54 CST; 28min ago
  Process: 9809 ExecStart=/usr/sbin/rpc.gssd $GSSDARGS (code=exited, status=0/SUCCESS)
 Main PID: 9810 (rpc.gssd)
   Memory: 804.0K
   CGroup: /system.slice/rpc-gssd.service
           └─9810 /usr/sbin/rpc.gssd
 
Jan 31 05:33:54 server.domain.com systemd[1]: Starting RPC security service for NFS client and server...
Jan 31 05:33:54 server.domain.com systemd[1]: Started RPC security service for NFS client and server.

Adding Domains in Certbot

You can register multiple domains to a single SSL certificate. This is particularly useful if you are hosting multiple domains on one server. This command adds more domains to your existing certificate.

certbot --expand -d existing.com -d newdomain1.com -d newdomain2.com

Check if the domains were added.

certbot certificates

Certbot certificates are valid for 90 days, but they automatically renew themselves if expiration is less than 30 days. If you need to renew manually for some odd reason, you can run this command. You can also perform a dry-run before renewing.

certbot renew
certbot renew --dry-run

Using Or on Regular Expressions

Here’s a regex using the pipe symbol as OR to allow only 6 possible values. 

regex="efs-(00|04|08|12|16|20)00"

Matches:

efs-0000
efs-0400
efs-0800
efs-1200
efs-1600
efs-2000

No matches:

efs-0100
efs-2200
efs-0600
efs-1400
efs-1800
efs-1110
111022
asdb023
2330asd
1200-efs
1205
abc

$var is compared with $regex to find a match. $var is any of the variables above.

if [[ $var != $regex ]]; then
  echo "Not a match"
else
  echo "It's a match"
fi