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====== generic cli command cheatsheet ======

===== OS version =====


==== find debian dist version ====
<code bash>
$ cat /etc/debian_version
11.5
</code>

==== find ubuntu dist version ====
<code bash>
$ lsb_release -a

No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.1 LTS
Release:	22.04
Codename:	jammy
</code>

==== find alpine dist version ====
<code bash>
$ sudo cat /etc/os-release

NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.16.2
PRETTY_NAME="Alpine Linux v3.16"
HOME_URL="https://alpinelinux.org/"
BUG_REPORT_URL="https://gitlab.alpinelinux.org/alpine/aports/-/issues"
</code>

===== sudo =====

==== sticky sudo ====
<code bash>
ubuntu@kamaradski:~$ sudo -i
root@kamaradski:~#
</code>

==== add user to sudo ====
<code bash>
# change to superuser
someuser@server$ su
password:

# add some user to sudo
root@server$ /sbin/usermod -aG sudo someuser

# confirm user is added
root@server$ getent group sudo
sudo:x:27:someuser

# test that it works
root@server$ su - someuser
someuser@server$ sudo whoami
[sudo] password for someuser:
root
</code>

===== user and group management =====

==== add user (interactive) ====

<code bash>
$ adduser kamaradski
Adding user `kamaradski' ...
Adding new group `kamaradski' (1000) ...
Adding new user `kamaradski' (1000) with group `kamaradski' ...
Creating home directory `/home/kamaradski' ...
Copying files from `/etc/skel' ...
New password: 
Retype new password: 
passwd: password updated successfully
Changing the user information for kamaradski
Enter the new value, or press ENTER for the default
        Full Name []: 
        Room Number []: 
        Work Phone []: 
        Home Phone []: 
        Other []: 
Is the information correct? [Y/n] y
</code>

===== RAM stats =====

==== type and speed of RAM ====
<code bash>
$ dmidecode --type 17 

# dmidecode 3.3
Getting SMBIOS data from sysfs.
SMBIOS 3.0.0 present.

Handle 0x0037, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0036
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 4 GB
        Form Factor: DIMM
        Set: None
        Locator: DIMM_A1
        Bank Locator: BANK 0
        Type: DDR4
        Type Detail: Synchronous
        Speed: 2400 MT/s
        Manufacturer: 859B
        Serial Number: 24C500AF9
        Asset Tag: 9876543210
        Part Number: CT4G4DFS824A.M8FE   
        Rank: 1
        Configured Memory Speed: 2133 MT/s
        Minimum Voltage: 1.2 V
        Maximum Voltage: 1.2 V
        Configured Voltage: 1.2 V

Handle 0x0038, DMI type 17, 40 bytes
Memory Device
        Array Handle: 0x0036
        Error Information Handle: Not Provided
        Total Width: 64 bits
        Data Width: 64 bits
        Size: 4 GB
        Form Factor: DIMM
        Set: None
        Locator: DIMM_B1
        Bank Locator: BANK 2
        Type: DDR4
        Type Detail: Synchronous
        Speed: 2400 MT/s
        Manufacturer: 859B
        Serial Number: 24C59B2F
        Asset Tag: 9876543210
        Part Number: CT4G4DFS824A.M8FE   
        Rank: 1
        Configured Memory Speed: 2133 MT/s
        Minimum Voltage: 1.2 V
        Maximum Voltage: 1.2 V
        Configured Voltage: 1.2 V
</code>

==== freeBSD => sorted list of processes by total size (res, swap, libraries etc etc) ====
<code bash>
$ top -S -w -o size
</code>

==== freeBSD => sorted list with top res (physical memory) ====
<code bash>
$ top -S -w -o res
</code>

==== freeBSD => sorted list by swap ====
<code bash>
$ top -S -w -o swap
</code>

===== cpu stats =====

==== find architeture ====
<code bash>
$ uname -m

# x86_64 => 64-bit version of the x86 (normal Intel or AMD) 
# aarch64 => shows with ubuntu in VM on Arm
# arm64 => apple M1/M2
</code>

==== find all cpu details ====
<code bash>
$ lscpu

Architecture:            x86_64
  CPU op-mode(s):        32-bit, 64-bit
  Address sizes:         39 bits physical, 48 bits virtual
  Byte Order:            Little Endian
CPU(s):                  2
  On-line CPU(s) list:   0,1
Vendor ID:               GenuineIntel
  Model name:            Intel(R) Celeron(R) 2955U @ 1.40GHz
    CPU family:          6
    Model:               69
    Thread(s) per core:  1
    Core(s) per socket:  2
    Socket(s):           1
    Stepping:            1
    CPU max MHz:         1400.0000
    CPU min MHz:         800.0000
    BogoMIPS:            2793.57
    Flags:               fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss
                         ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc
                         cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg cx16 xtpr pdcm pcid sse4_1 sse4_2
                         movbe popcnt tsc_deadline_timer xsave rdrand lahf_lm abm cpuid_fault epb invpcid_single pti ssbd ibrs ibpb sti
                         bp tpr_shadow vnmi flexpriority ept vpid ept_ad fsgsbase tsc_adjust erms invpcid xsaveopt dtherm arat pln pts
                         md_clear flush_l1d
Virtualization features:
  Virtualization:        VT-x
Caches (sum of all):
  L1d:                   64 KiB (2 instances)
  L1i:                   64 KiB (2 instances)
  L2:                    512 KiB (2 instances)
  L3:                    2 MiB (1 instance)
NUMA:
  NUMA node(s):          1
  NUMA node0 CPU(s):     0,1
Vulnerabilities:
  Itlb multihit:         KVM: Mitigation: VMX disabled
  L1tf:                  Mitigation; PTE Inversion; VMX conditional cache flushes, SMT disabled
  Mds:                   Mitigation; Clear CPU buffers; SMT disabled
  Meltdown:              Mitigation; PTI
  Mmio stale data:       Unknown: No mitigations
  Retbleed:              Not affected
  Spec store bypass:     Mitigation; Speculative Store Bypass disabled via prctl and seccomp
  Spectre v1:            Mitigation; usercopy/swapgs barriers and __user pointer sanitization
  Spectre v2:            Mitigation; Retpolines, IBPB conditional, IBRS_FW, STIBP disabled, RSB filling, PBRSB-eIBRS Not affected
  Srbds:                 Mitigation; Microcode
  Tsx async abort:       Not affected

</code>

===== time sync =====

related config file: /etc/systemd/timesyncd.conf

==== current time ====
<code bash>
$ date
Sat Nov 12 14:57:27 CET 2022
</code>

==== check state ====
<code bash>
$ timedatectl

               Local time: Mon 2022-10-31 17:39:26 CET
           Universal time: Mon 2022-10-31 16:39:26 UTC
                 RTC time: Mon 2022-10-31 16:39:26
                Time zone: Europe/Berlin (CET, +0100)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

</code>

==== detailed status ====
<code bash>
$ systemctl status systemd-timesyncd

● systemd-timesyncd.service - Network Time Synchronization
     Loaded: loaded (/lib/systemd/system/systemd-timesyncd.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2022-11-15 20:27:34 CET; 58min ago
       Docs: man:systemd-timesyncd.service(8)
   Main PID: 2680819 (systemd-timesyn)
     Status: "Initial synchronization to time server 51.75.67.47:123 (pool.ntp.org)."
      Tasks: 2 (limit: 1068)
     Memory: 1.2M
        CPU: 51ms
     CGroup: /system.slice/systemd-timesyncd.service
             └─2680819 /lib/systemd/systemd-timesyncd

Nov 15 20:27:34 hostname systemd[1]: Starting Network Time Synchronization...
Nov 15 20:27:34 hostname systemd-timesyncd[2680819]: Invalid PollIntervalMinSec=. Using default value.
Nov 15 20:27:34 hostname systemd-timesyncd[2680819]: PollIntervalMaxSec= is smaller than PollIntervalMinSec=. Using default value.
Nov 15 20:27:34 hostname systemd[1]: Started Network Time Synchronization.
Nov 15 20:27:45 hostname systemd-timesyncd[2680819]: Timed out waiting for reply from 172.67.191.29:123 (ntp.somewhere.com).
Nov 15 20:27:55 hostname systemd-timesyncd[2680819]: Timed out waiting for reply from 104.21.60.32:123 (ntp.somewhere.com).
Nov 15 20:28:05 hostname systemd-timesyncd[2680819]: Timed out waiting for reply from [2606:4700:3037::6815:3c20]:123 (ntp.somewhere.com).
</code>

==== set timezone ====
<code bash>
$ sudo timedatectl set-timezone America/New_York
</code>

==== turn ntp on (22.04 and above) ====
<code bash>
$ sudo timedatectl set-ntp on
</code>

===== wc (word count) =====

==== count of string lenght ====
<code bash>
$ echo "some-very-long-string" | wc -c
22
</code>

===== lsof (list open files) =====

==== list anything that is listing on a specific port ====
<code bash>
$ sudo lsof -i :53

COMMAND   PID            USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
systemd-r 629 systemd-resolve   13u  IPv4  16505      0t0  UDP localhost:domain
systemd-r 629 systemd-resolve   14u  IPv4  16506      0t0  TCP localhost:domain (LISTEN)
</code>

===== curl =====

==== download a file (and follow any redirects) ====
<code bash>
$ curl -LO https://path.to/some/file.tar.gz
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
  0     0    0     0    0     0      0      0 --:--:-- --:--:-- --:--:--     0
100 11.0M  100 11.0M    0     0  6226k      0  0:00:01  0:00:01 --:--:-- 10.9M
</code>

===== symlink =====

==== create symlink ====
<code bash>
$ ln /path/some/source.file /path/target/link.name

use -f to force a new symlink (overwrite)
use -s for a soft-link
</code>

===== zip/tar/etc =====

==== un-tar file, keep same structure ====
<code bash>
$ tar -xvf some_file.tar.gz

./somefolderinsidethezip/
./somefolderinsidethezip/file1
./somefolderinsidethezip/file2.txt
</code>

===== scp =====

==== from remote to local ====
<code bash>
$ scp user@remotehost:/source/folder/file.ext /local/target/folder/
file.ext                  15% 5706MB  56.8MB/s   09:21 ETA
</code>

==== from local to remote host ====
<code bash>
$ scp /local/file.ext user@remotehost:/remote/target/folder/
file.ext                      8% 3191MB  18.1MB/s   31:36 ETA
</code>

==== notes ====
- By default, when the target on the remote system is a directory and you don't provide a filename, scp expects that the source file name should be used. However, you must ensure that the directory path does not include a trailing slash if you don't specify the filename explicitly.  

- Make sure to always use proper paths for the files you are copying. For example for a file in the local folder from where you are issuing the command use "./local.file" instead of just "local.file". This will prevent issues with SCP misinterpreting your intentions.
===== other =====

==== track the output of a command by executing it every x-time ====
<code bash>
$ watch -n 1 docker ps

#display the output of "docker ps" and update it every 1 second (-n 1) including a screen refresh/clear. default to 2sec without -n parameter.
</code>
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