Linux Commands: The Obscure Ones
May 03, 2023
sudo !!
Damn I forgot to use sudo (maybe I should just log in as root?).
No! Just use this bad boy.
fontora@banshee:~$ systemctl daemon-reload
==== AUTHENTICATING FOR org.freedesktop.systemd1.reload-daemon ===
Authentication is required to reload the systemd state.
Authenticating as: fontora
Password:
fontora@banshee:~$ sudo !!
sudo systemctl daemon-reload
mtr
My Traceroute .. it’s like traceroute but better.
fontora@banshee:~$ mtr google.com
My traceroute [v0.95]
banshee (129.24.56.77) -> google.com (172.217.24.46) 2023-05-03T13:06:06+1000
Keys: Help Display mode Restart statistics Order of fields quit
Packets Pings
Host Loss% Snt Last Avg Best Wrst StDev
1. ns1rtr1-ten-lan.binarylane.cloud 6.2% 16 0.3 0.3 0.2 0.4 0.0
2. 74.125.52.4 0.0% 16 0.6 1.2 0.4 7.0 1.8
3. 108.170.247.81 0.0% 16 1.0 1.0 0.8 2.1 0.3
4. 216.239.57.119 0.0% 15 1.3 1.2 1.1 1.3 0.1
5. syd15s20-in-f14.1e100.net 0.0% 15 0.8 0.7 0.7 0.9 0.1
namei
Intended for troubleshooting symlink hell, can be useful to troubleshoot permissions.
fontora@banshee:~$ namei -l /etc/ssh/sshd_config
f: /etc/ssh/sshd_config
drwxr-xr-x root root /
drwxr-xr-x root root etc
drwxr-xr-x root root ssh
-rw-r--r-- root root sshd_config
stat
ls -l is for chumps.
fontora@banshee:~$ stat /etc/ssh/sshd_config
File: /etc/ssh/sshd_config
Size: 3256 Blocks: 8 IO Block: 4096 regular file
Device: fc01h/64513d Inode: 791 Links: 1
Access: (0644/-rw-r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2023-04-29 18:42:33.932000000 +1000
Modify: 2022-07-22 12:28:12.779931939 +1000
Change: 2022-07-22 12:28:12.779931939 +1000
Birth: 2022-07-22 12:28:12.779931939 +1000
pstree vs ps
Do you like pstree? Meh.
Do you like ps? Correct!
fontora@banshee:~# ps -eF f
Bonus points if you do something like ps –ppid 2 -NF f
man ascii
Pretty useful.
fontora@banshee:~$ man ascii
...
Oct Dec Hex Char Oct Dec Hex Char
────────────────────────────────────────────────────────────────────────
000 0 00 NUL '\0' (null character) 100 64 40 @
001 1 01 SOH (start of heading) 101 65 41 A
002 2 02 STX (start of text) 102 66 42 B
003 3 03 ETX (end of text) 103 67 43 C
004 4 04 EOT (end of transmission) 104 68 44 D
005 5 05 ENQ (enquiry) 105 69 45 E
006 6 06 ACK (acknowledge) 106 70 46 F
007 7 07 BEL '\a' (bell) 107 71 47 G
010 8 08 BS '\b' (backspace) 110 72 48 H
011 9 09 HT '\t' (horizontal tab) 111 73 49 I
012 10 0A LF '\n' (new line) 112 74 4A J
013 11 0B VT '\v' (vertical tab) 113 75 4B K
014 12 0C FF '\f' (form feed) 114 76 4C L
015 13 0D CR '\r' (carriage ret) 115 77 4D M
...
vmstat
Another tool for checking performance (use htop if you’re not btw).
Dummies guide: If the second last column (CPU wait) is never not zero, it’s bad.
fontora@banshee:~$ vmstat 5 5
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
r b swpd free buff cache si so bi bo in cs us sy id wa st
0 0 0 113484 63620 588460 0 0 4 7 24 43 0 0 100 0 0
0 0 0 113484 63624 588460 0 0 0 33 36 56 0 0 99 0 0
1 0 0 113484 63624 588464 0 0 1 0 42 81 1 0 99 0 0
0 0 0 113484 63632 588464 0 0 0 8 32 54 0 0 100 0 0
0 0 0 113484 63632 588464 0 0 0 0 24 40 0 0 100 0 0
vimdiff
It’s like diff… but better in every way.
fontora@banshee:~$ vimdiff /etc/ca-certificates.conf /etc/ca-certificates.conf.dpkg-old
video