Category: admin

pgrep looks through the currently running processes and lists the process IDs. Use

pgrep -f 'process_name'

to find the process ID of a process.

To create a user (sftp) with readonly  access via sftp to a single directory (/var/sftp_readonly), perform the following steps:

sudo su #become root

useradd sftp #create new user

passwd sftp #set a password

groupadd sftp_readonly #create a group

mkdir /var/sftp_readonly #create a directory

usermod -G sftp_readonly sftp # add user to group

chmod 755 /var/sftp_readonly/ #allow others to read

cp /etc/ssh/sshd_config ~/sshd_config.bck #backup your ssh config

editor  /etc/ssh/sshd_config # edit your ssh_config

Add the following lines to the bottom of /etc/ssh/sshd_config

Match Group sftp_readonly
  X11Forwarding no
  AllowTcpForwarding no
  ChrootDirectory /var/sftp_readonly/
  ForceCommand internal-sftp

Also make sure that the following line is present

Subsystem sftp internal-sftp

Reload your ssh service

sudo service ssh reload

The unix tool date can be used to print the current date. It also can be used to calculate time spans or to reformat time strings.

Examples:
1. Print the current date in a conventional form

date +"%d. %B %Y"

2. Use certain locale. Find supported list in /usr/share/i18n/SUPPORTED

LANG=de_DE.UTF-8 date +"%d. %B %Y"

3. Print an arbitrary (but valid) timestring in a conventional form

date -d 2003-11-22 +"%d. %B %Y"

4. Print the current date as seconds since 1970 (unix epoche)

date +%s

5. Calculate the difference of two dates in days. Explanation can be found here.

A="2002-10-20"
B="2003-11-22"
echo $(( ($(date -d $B +%s) - $(date -d $A +%s)) / 86400 )) days

6. Print seconds after 1970 (unix epoche) in a conventional form.

TZ=UTC LANG=en_EN.UTF-8  date -d@0 +"%H:%M:%S %d. %B %Y"

Note: if TZ=UTC is left out, date will add or subtract an offset in accordance to systems timezone.

7. Find timezone offset

OFF_1=$(date -d '1 Jan' +%z)
OFF_7=$(date -d '1 Jul' +%z)
echo $OFF_1 $OFF_7

The unix tool yes provides one simple yet very useful functionality. It repeatedly  prints ‘yes’ (or any other string) to the console.

This can be used to automatically answer questions in scripted environments.

Example:

yes|sudo rpm -ivh mysql-community-release-el7-5.noarch.rpm