Very useful and informative Linux commands.

While running Linux, if you want to list the contents of a folder in a vertical list format, just use the ls command with these switches.

[email protected]:~$ ls -luh --color=yes
total 48K
drwxr-xr-x 2 jason jason 4.0K Dec 15 03:03 Desktop
drwxr-xr-x 2 jason jason 4.0K Nov 29 17:00 Documents
drwxr-xr-x 2 jason jason 4.0K Nov 29 17:29 Downloads
-rw-r--r-- 1 jason jason 8.8K Nov 25 20:57 examples.desktop
drwxr-xr-x 2 jason jason 4.0K Nov 25 21:18 Music
-rw-r--r-- 1 jason jason  459 Dec  7 17:21 partsize
drwxr-xr-x 2 jason jason 4.0K Nov 25 21:19 Pictures
drwxr-xr-x 2 jason jason 4.0K Nov 25 21:18 Public
drwxr-xr-x 2 jason jason 4.0K Dec 15 03:03 Templates
drwxr-xr-x 2 jason jason 4.0K Nov 25 21:18 Videos

then you get the directory listing with human readable file sizes instead of being listed in bytes.

To list the partitions on a disk, just type

sudo fdisk -l /dev/sda

for example and it will list the partitions on the device. You need superuser priviledges to run this command. Then you get the output below.

[email protected]:~$ sudo fdisk -l /dev/sda
[sudo] password for jason: 
 
Disk /dev/sda: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders, total 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000d5c84
 
   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *        2048    39845887    19921920   83  Linux
/dev/sda2        39847934    41940991     1046529    5  Extended
/dev/sda5        39847936    41940991     1046528   82  Linux swap / Solaris

A very useful command. This is useful when I am double checking which partition to install Linux to on my hard drive so I do not overwrite the wrong partition.

Get CPU information from your machine using the cat /proc/cpuinfo command.

[email protected]:~$ cat /proc/cpuinfo 
processor	: 0
vendor_id	: GenuineIntel
cpu family	: 6
model		: 60
model name	: Intel(R) Core(TM) i5-4670K CPU @ 3.40GHz
stepping	: 3
microcode	: 0x9
cpu MHz		: 3399.030
cache size	: 6144 KB
physical id	: 0
siblings	: 1
core id		: 0
cpu cores	: 1
apicid		: 0
initial apicid	: 0
fpu		: yes
fpu_exception	: yes
cpuid level	: 13
wp		: yes
flags		: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts mmx fxsr sse sse2 ss syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts nopl xtopology tsc_reliable nonstop_tsc aperfmperf eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm ida arat xsaveopt pln pts dtherm fsgsbase tsc_adjust bmi1 avx2 smep bmi2 invpcid
bogomips	: 6798.06
clflush size	: 64
cache_alignment	: 64
address sizes	: 42 bits physical, 48 bits virtual
power management:

List all users on your Linux machine.

[email protected]:~$ sudo cut -d: -f1 /etc/passwd
[sudo] password for jason: 
root
daemon
bin
sys
sync
games
man
lp
mail
news
uucp
proxy
www-data
backup
list
irc
gnats
nobody
libuuid
syslog
messagebus
usbmux
dnsmasq
avahi-autoipd
kernoops
rtkit
saned
whoopsie
speech-dispatcher
avahi
lightdm
colord
pulse
hplip
jason
ntp

List all users with passwords in the /etc/shadow file.

[email protected]:~$ sudo awk 'length($0)>42' /etc/shadow
root:$6$94h9BlHF$xGJjZIKlOVfuDc4V7pXzc7Qhy3YUjthc3Qusj5axc6l1HpUFgCNbk0MybBKfP7Oj9zraEGV6w8aEA5gHuipcW.:16784:0:99999:7:::
jason:$1$/.DJdFfa$AdDAUD25jfdDBtS4vxfL5/:16765:0:99999:7:::

List all users on your Linux machine that can actually login, not system users.

[email protected]:~$ sudo awk -F':' '$2 ~ "\$" {print $1}' /etc/shadow
root
jason

Another way to list all users on your system with passwords, with the exception of the root user.

[email protected]:~$ sudo awk -F'[/:]' '{if ($3 >= 1000 && $3 != 65534) print $1}' /etc/passwd
jason

Another version. This will list all users with a UID over 500.

[email protected]:~$ sudo awk -F'[/:]' '{if ($3 >= 500 && $3 != 65534) print $1}' /etc/passwd
jason
1 responses to “Very useful and informative Linux commands.

Very nice and Informative, preparing for Linux Certification, wanted to learn some Linux Commands, can anyone suggest me some books and videos?

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