Databases, Systems & Networks

I am a new Ubuntu Linux laptop user. I setup my computer name to ‘tom’ during installation but now I would like to change the computer name to ‘jerry’. Can you tell me how do I I remove tom and set it to jerry on Ubuntu Linux? How do I change the Ubuntu computer name from ‘ubuntu’ to ‘AvlinStar’? Can you tell me more about Ubuntu Linux change hostname command?

You can use the hostname command to see or set the system’s host name. The host name or computer name is usually at system startup in /etc/hostname file. Open the terminal application and type the following commands to set or change hostname or computer name on Ubuntu.

Display the current Ubuntu hostname

Simply type the following command:
$ hostname
Sample outputs:

Ubuntu change hostname command

The procedure to change the computer name on Ubuntu Linux:

1. Type the following command to edit /etc/hostname using nano or vi text editor:
   sudo nano /etc/hostname
   Delete the old name and setup new name.
2. Next Edit the /etc/hosts file:
   sudo nano /etc/hosts
   Replace any occurrence of the existing computer name with your new one.
3. Reboot the system to changes take effect:
   sudo reboot

Sample outputs:

How to change the Ubuntu server hostname without a system restart?

Type the following commands:
$ sudo hostname new-server-name-here
Next edit the /etc/hostname file and update hostname:
$ sudo nano /etc/hostname
Finally, edit the /etc/hosts file and update the lines that reads your old-host-name:
$ sudo nano /etc/hosts
From:
127.0.1.1 old-host-name
To:
127.0.1.1 new-server-name-here
Save and close the file.

Ubuntu Linux Change Hostname Using hostnamectl

Systemd based Linux distro such as Ubuntu Linux 16.04 LTS and above can simply use the hostnamectl command to change hostname. To see current setting just type the following command:
$ hostnamectl
Sample outputs:

   Static hostname: nixcraft
         Icon name: computer-laptop
           Chassis: laptop
        Machine ID: 291893e6499e4d99891c3cf4b70a138b
           Boot ID: 9fda2365b77841649e40a141fde46537
  Operating System: Ubuntu 17.10
            Kernel: Linux 4.13.0-21-generic
      Architecture: x86-64

To change hostname from nixcraft to viveks-laptop, enter:
$ hostnamectl set-hostname viveks-laptop
$ hostnamectl

System administrators (sysadmins) are responsible for day-to-day operations of production systems and services. One of the critical roles of sysadmins is to ensure that operational services are available round the clock. For that, they have to carefully plan backup policies, disaster management strategies, scheduled maintenance, security audits, etc. Like every other discipline, sysadmins have their tools of trade. Utilizing proper tools in the right case at the right time can help maintain the health of operating systems with minimal service interruptions and maximum uptime.

This article will present some of the most popular and useful CLI tools recommended for sysadmins in their day to day activities. If you would like to recommend any useful tool which is not listed here, don’t forget to share it in the comment section.

Network Tools

1. ping: Check end-to-end connectivity (RTT delay, jitter, packet loss) of a remote host with ICMP echo/reply. Useful to check system status and reachability.

2. hping: Network scanning and testing tool that can generate ICMP/TCP/UDP ping packets. Often used for advanced port scanning, firewall testing, manual path MTU discovery and fragmentation testing.

3. traceroute: Discover a layer-3 forwarding path from a local host to a remote destination host with TTL-limited ICMP/UDP/TCP probe packets. Useful to troubleshoot network reachability and routing problems.

4. mtr: A variation of traceroute which characterizes per-hop packet loss/jitter with running statistics. Useful to characterize routing path delays.

5. netcat/socat: A swiss army knife of TCP/IP networking, allowing to read/write byte streams over TCP/UDP. Useful to troubleshoot firewall policies and service availability.

6. dig: DNS troubleshooting tool that can generate forward queries, reverse queries, find authoritative name servers, check CNAME, MX and other DNS records. Can be instructed to query a specific DNS server of your choosing.

7. nslookup: Another DNS checking/troubleshooting tool. Works with all DNS queries and records. Can query a particular DNS server.

8. dnsyo: A DNS testing tool which checks DNS propagation by performing DNS lookup from over a number of open resolvers located across 1,500 different networks around the world.

9. lsof: Show information about files (e.g., regular files, pipes or sockets) which are opened by processes. Useful to monitor processes or users in terms of their open network connections or opened files.

10. iftop: A ncurses-based TUI utility that can be used to monitor in real time bandwidth utilization and network connections for individual network interfaces. Useful to keep track of bandwidth hogging applications, users, destinations and ports.

11. netstat: A network statistics utility that can show status information and statistics about open network connections (TCP/UDP ports, IP addresses), routing tables, TX/RX traffic and protocols. Useful for network related diagnosis and performance tuning.

12. tcpdump: A popular packet sniffer tool based on libpcap packet capture library. Can define packet capturing filters in Berkeley Packet Filters format.

13. tshark: Another CLI packet sniffer software with full compatibility with its GUI counterpart, Wireshark. Supports 1,000 protocols and the list is growing. Useful to troubleshoot, analyze and store information on live packets.

14. ip: A versatile CLI networking tool which is part of iproute2 package. Used to check and modifying routing tables, network device state, and IP tunneling settings. Useful to view routing tables, add/remove static routes, configure network interfaces, and otherwise troubleshoot routing issues.

15. ifup/ifdown: Used to bring up or shut down a particular network interface. Often a preferred alternative to restarting the entire network service.

16. autossh: A program which creates an SSH session and automatically restarts the session should it disconnect. Often useful to create a persistent reverse SSH tunnel across restrictive corporate networks.

17. iperf: A network testing tool which measures maximum bi-directional throughput between a pair of hosts by injecting customizable TCP/UDP data streams in between.

18. elinks/lynx: text-based web browsers for CLI-based server environment.

Lire la suite…

Source: BinaryTides

Hardware information

Like for every thing, there are plenty of commands to check information about the hardware of your linux system. Some commands report only specific hardware components like cpu or memory while the rest cover multiple hardware units.

This post takes a quick look at some of the most commonly used commands to check information and configuration details about various hardware peripherals and devices. The list includes lscpu, hwinfo, lshw, dmidecode, lspci etc.

1. lscpu

The lscpu command reports information about the cpu and processing units. It does not have any further options or functionality.

$ lscpu
Architecture:          x86_64
CPU op-mode(s):        32-bit, 64-bit
Byte Order:            Little Endian
CPU(s):                4
On-line CPU(s) list:   0-3
Thread(s) per core:    1
Core(s) per socket:    4
Socket(s):             1
NUMA node(s):          1
Vendor ID:             GenuineIntel
CPU family:            6
Model:                 23
Stepping:              10
CPU MHz:               1998.000
BogoMIPS:              5302.48
Virtualization:        VT-x
L1d cache:             32K
L1i cache:             32K
L2 cache:              2048K
NUMA node0 CPU(s):     0-3

2. lshw – List Hardware

A general purpose utility, that reports detailed and brief information about multiple different hardware units such as cpu, memory, disk, usb controllers, network adapters etc. Lshw extracts the information from different /proc files.

$ sudo lshw -short

H/W path        Device      Class       Description
===================================================
                            system      ()
/0                          bus         DG35EC
/0/0                        processor   Intel(R) Core(TM)2 Quad CPU    Q8400  @ 2.66GHz
/0/0/1                      memory      2MiB L2 cache
/0/0/3                      memory      32KiB L1 cache
/0/2                        memory      32KiB L1 cache
/0/4                        memory      64KiB BIOS
/0/14                       memory      8GiB System Memory
/0/14/0                     memory      2GiB DIMM DDR2 Synchronous 667 MHz (1.5 ns)
/0/14/1                     memory      2GiB DIMM DDR2 Synchronous 667 MHz (1.5 ns)
/0/14/2                     memory      2GiB DIMM DDR2 Synchronous 667 MHz (1.5 ns)
/0/14/3                     memory      2GiB DIMM DDR2 Synchronous 667 MHz (1.5 ns)
/0/100                      bridge      82G35 Express DRAM Controller
/0/100/2                    display     82G35 Express Integrated Graphics Controller
/0/100/2.1                  display     82G35 Express Integrated Graphics Controller
/0/100/19       eth0        network     82566DC Gigabit Network Connection
/0/100/1a                   bus         82801H (ICH8 Family) USB UHCI Controller #4
/0/100/1a.1                 bus         82801H (ICH8 Family) USB UHCI Controller #5
/0/100/1a.7                 bus         82801H (ICH8 Family) USB2 EHCI Controller #2
/0/100/1b                   multimedia  82801H (ICH8 Family) HD Audio Controller
/0/100/1c                   bridge      82801H (ICH8 Family) PCI Express Port 1
/0/100/1c.1                 bridge      82801H (ICH8 Family) PCI Express Port 2
/0/100/1c.2                 bridge      82801H (ICH8 Family) PCI Express Port 3
/0/100/1c.2/0               storage     JMB368 IDE controller
/0/100/1d                   bus         82801H (ICH8 Family) USB UHCI Controller #1
/0/100/1d.1                 bus         82801H (ICH8 Family) USB UHCI Controller #2
/0/100/1d.2                 bus         82801H (ICH8 Family) USB UHCI Controller #3
/0/100/1d.7                 bus         82801H (ICH8 Family) USB2 EHCI Controller #1
/0/100/1e                   bridge      82801 PCI Bridge
/0/100/1e/5                 bus         FW322/323 [TrueFire] 1394a Controller
/0/100/1f                   bridge      82801HB/HR (ICH8/R) LPC Interface Controller
/0/100/1f.2                 storage     82801H (ICH8 Family) 4 port SATA Controller [IDE mode]
/0/100/1f.3                 bus         82801H (ICH8 Family) SMBus Controller
/0/100/1f.5                 storage     82801HR/HO/HH (ICH8R/DO/DH) 2 port SATA Controller [IDE m
/0/1            scsi3       storage     
/0/1/0.0.0      /dev/sda    disk        500GB ST3500418AS
/0/1/0.0.0/1    /dev/sda1   volume      70GiB Windows NTFS volume
/0/1/0.0.0/2    /dev/sda2   volume      395GiB Extended partition
/0/1/0.0.0/2/5  /dev/sda5   volume      97GiB HPFS/NTFS partition
/0/1/0.0.0/2/6  /dev/sda6   volume      97GiB Linux filesystem partition
/0/1/0.0.0/2/7  /dev/sda7   volume      1952MiB Linux swap / Solaris partition
/0/1/0.0.0/2/8  /dev/sda8   volume      198GiB Linux filesystem partition
/0/3            scsi4       storage     
/0/3/0.0.0      /dev/cdrom  disk        DVD RW DRU-190A

Check out the following post to learn more about lshw

Get hardware information on Linux with lshw command

Lire la suite…

“inotify”, Remplaçant de “dnotify”, est une technologie, intégrée au noyau Linux (>=2.6.13) , destinée à notifier les événements, modifications, accès, etc, effectués sur le contenu d’un système de fichiers en ce basant sur le contrôle des “inodes” (structures de données contenant des informations sur les fichiers d’un systèmes de fichiers).

« incron« , Pour « INotify CRON », permet d’exploiter les informations « d’inotify » afin d’effectuer une action, commande(s), scripts, etc, en cas de modifications de fichiers ou de répertoires donnés.

Installation de inotify

« inotify » Est intégré au noyau et est activé dans les kernels fournis par les distributions.

« incron » Est, de son côté, empaqueté sur la plupart des distributions mais nécessitera, sur Red Hat et ses dérivées (CentOS, Scientific Linux, etc) l’ajout des miroirs EPEL (« Extra Packages for Enterprise Linux » voir « Ajout des miroirs EPEL (Extra Packages for Enterprise Linux) sous Red Hat like (CentOS, RHEL, SL, …) » sur Admin Linux). L’installation s’effectue via le gestionnaire de paquet de votre distribution.

Sous Ubuntu, Debian et ses dérivés :

# apt-get install incron

Sous les dérivés de Red Hat :

# yum install incron

Sous Gentoo Linux « emerge » se chargera de l’installation tous comme « pacman » le fera très bien sous Arch Linux.

Lire la suite…

Source: ServerDensity

The industry is hotting up at the moment, and there are more tools than you can shake a stick at. Here lies the most comprehensive list on the Internet (of monitoring tools). Featuring over 80 ways to monitor your machines. Within this article we outline:

• Command line tools
• Network related
• System related monitoring
• Log monitoring tools
• Infrastructure monitoring tools

It’s hard work monitoring and debugging performance problems, but it’s easier with the right tools at the right time. But how much of your valuable time do you think it would take you to investigate all of these tools and find out which one is best for you?

Why not check out Server Density first, it has a beautiful UI, an api that’s easy to use and alerts that will keep downtime to a minimum.

Top 10  System Monitoring Tools

1. Top

This is a small tool which is pre-installed in many unix systems. When you want an overview of all the processes or threads running in the system: top is a good tool. You can order these processes on different criteria and the default criteria is CPU.

2. htop

Htop is essentially an enhanced version of top. It’s easier to sort by processes. It’s visually easier to understand and has built in commands for common things you would like to do. Plus it’s fully interactive.

3. atop

Atop monitors all processes much like top and htop, unlike top and htop however it has daily logging of the processes for long-term analysis. It also shows resource consumption by all processes. It will also highlight resources that have reached a critical load.

4. apachetop

Apachetop monitors the overall performance of your apache webserver. It’s largely based on mytop. It displays current number of reads, writes and the overall number of requests processed.

5. ftptop

ftptop gives you basic information of all the current ftp connections to your server such as the total amount of sessions, how many are uploading and downloading and who the client is.

Lire la suite…