S3E20: "Clockulators"

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2018-11-24 03:19:43 2018-12-03 03:28:45 "Edita"
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MP3 33e344cd7650f3308414ebd45e81e06ae26527710b0519f8ee6edb50ce360c28 click click
OGG 379de39d31f07d9ac1f1272df63cad1579394c91cef78f4cddb000fd50306b01 click click

In this episode, we talk about various timing tools in *nix (at, cron, systemd timers, NTP, etc.)

News

Notes

Starts at 14m07s.

I was drinking another Porterhouse’s An Brain Blásta. Paden was drinking water. Jthan was drinking Coors’ Light (which yes, Jthan, we did have on in S1E13 and S3E0).

  • Time-related tools in *NIX!
    • at
      • Automated one-time execution of commands (scripts, etc.).
      • Useful beginner’s guides can be found here and here, but it’s also in the RUTE and the pink book (see S0E11 notes for links to these).
    • cron(d)
      • You can find a crontab/cronjob parser here, you can find a generator here.
      • The ArchWiki documentation is great.
      • You cannot specify a specific year, Jthan, just how many times a year (down to once a year).
    • anacron
      • Relatedly, anacron is a form of alternate cron that helps you out on machines that are more sporadic with availability. Cronie provides both a crond and anacron interface, but more traditional cronds (such as Paul Vixie’s crond) require a separate or standalone anacron.
    • systemd Timers
      • The Arch wiki is still great, but the upstream docs aren’t too bad either.
      • The challange I posed to Jthan is actually more or less exactly given as an example in the Arch wiki article here.
        • Someone remind me to write a cron to systemd timer converter.
    • NTP
      • NTPv3 is defined in RFC 1305 and NTPv4 is defined in RFC 5905 (proposed).
      • There is a history of security issues related to NTP.
      • Manages a way to bring computers in line with a more reliable timekeeping source (such as NIST’s ytterbium atomic clock), and addressing the tendency to correct the “loose” timekeeping methods consumer timekeeping hardware keeps.
      • VERY important for encryption sessions (handshaking, etc.) and PKI such as X.509!
    • Protip, some DHCP clients, if they support BOOTP, can get their NTP server from DHCP.
      • And in DNSMASQ, you can even reference it by name: dhcp-option=option:ntp-server,1.1.1.1,2.2.2.2 would send the NTP servers 1.1.1.1 and 2.2.2.2.

Sysbadministration Award

In this segment, we highlight system administration mistakes. Think of them as the IT equivalent of the Darwin Awards. (46m20s)

While I love Calibre for my e-reader, the author is nuts. He thinks he can maintain python 2 all by himself (and that it’d be “less work” than converting the codebase).

Errata

  • I ignore Jthan at the beginning because no, we never did talk about NTP. We briefly mention OpenNTPD in S0E13, though.
  • I forgot to mention it on-air, but did you know that ESR (author of The Cathedral and the Bazaar) is the project tech lead of a hardened NTP implementation called NTPsec?
  • Jthan does indeed have a shitton of crons:
22:06:08< jthan> root@[redacted]:/root# crontab -l | wc -l 
22:06:09< jthan> 2209
22:13:51< jthan> +
22:13:51< jthan> -bash-4.3$ crontab -l | wc -l 
22:13:51< jthan>     1880

Music

Music Credits
Track Title Artist Link Copyright/License
Intro Whosi sawsquarenoise click CC-BY 4.0
Outro 66666666666666666666 66666666666666666666 66666666666666666666 66666666666666666666 66666666666666666666 66666666666666666666 Monplaisir click CC0 1.0
(All music is royalty-free, properly licensed for use, used under fair use, or public domain.)

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