When analyzing the output of a bash script, it can be useful to prepend timestamp before each line to see how long it’s taking to do a specific action.

For this, you can use the ‘ts‘ command:

# echo -e "this\nis\na\ntest" | ts '[%Y-%m-%d %H:%M:%S]'
[2019-05-13 09:14:28] this
[2019-05-13 09:14:28] is
[2019-05-13 09:14:28] a
[2019-05-13 09:14:28] test

If the command ‘ts‘ is not available, you might need to install the package moreutils.

Seeing that error in HTTPd/Apache logs when trying to GET some pages?

(13)Permission denied: [client xxxxx]: access to /html/myfile.html denied because search permissions are missing on a component of the path

This is because of some SELinux policies blocking the calls. If you don’t want to turn SELinux off, a simple workaround is:

chcon -R --type=httpd_sys_rw_content_t /html/

When updating or installing a package on a Debian-based distribution, you can face that alert:

W: GPG error: http://ppa.launchpad.net trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C2518248EEA14886

This just means that a signing GPG key is missing or expired on your system. The error is giving you the ID of the missing key that you can use for looking for it on the Ubuntu website:

http://keyserver.ubuntu.com:11371/pks/lookup?op=get&search=0xC2518248EEA14886

Copy the key that you just got from the website above into a file – mykey.txt, for example – and import it with the apt-key command:

apt-key add mykey.txt

Try to install/update the package again, and the error should not appear anymore.

The PKCS12 format is replacing the old PFX format from Microsoft. This format will allow storage of X.509 private keys and the associated public certificates in a single encrypted file.

So you can extract the key and the certificate in a single common PEM file, you can use this openssl command:

openssl pkcs12 -in myCertificate.pfx -out myCertificateAndMyKey.pem

If you want to extract the key and the certificate independently, you can also use the options nocerts/nokeys along with openssl, to extract only one part:

openssl pkcs12 -in myCertificate.pfx -nocerts -out myCertificate.key
openssl pkcs12 -in myCertificate.pfx -nokeys -out myCertificate.pem

When doing update on a Debian/Ubuntu server, if a package is trying to modify a config file, it’s asking for a manual choice. If you’re trying to try to automate the process, you’d probably like to get rid of that ask and keep the current config file by default.

For that, you can use that script:

#!/bin/bash
apt-get update
listUpgrades=`apt list --upgradable |grep upgradable |cut -d/ -f1`
execUpgrades="DEBIAN_FRONTEND=noninteractive apt-get --yes --assume-yes -o DPkg::options::=\"--force-confdef\" -o DPkg::options::=\"--force-confold\" --only-upgrade install "$listUpgrades
eval $execUpgrades

The multiple options will enforce the update to keep current config and not overwrite it with the package default one.