Tag Archives: uptime

UNIX & Linux

Too good to #0012

Today: Mounting tar archives, a novel take on uptime, ipxe escapes.

ratarmount – Access large archives as a filesystem efficiently, e.g., TAR, RAR, ZIP, GZ, BZ2, XZ, ZSTD archives

$ virtualenv ~/.local/ratarmount
$ ~/.local/ratarmount/bin/pip3 install -U ratarmount
$ ~/.local/ratarmount/bin/ratarmount
$ install -D ~/.local/ratarmount/bin/ratarmount ~/bin/

$ mkdir -p ~/mnt
$ curl -O https://data.iana.org/time-zones/tzdata-latest.tar.gz
$ ratarmount tzdata-latest.tar.gz ~/mnt
$ find ~/mnt
$ fusermount -u ~/mnt

tuptime – Report historical and statistical real time of the system, keeping it between restarts. Total uptime

tuptime calculates overall uptime of the system it’s running on. It also flags shutdowns as “BAD” if it comes up without having been gracefully stopped before.

As I grew up in an age where uptime braggery was common even among professionals, my entirely unreasonable use case here is to determine uptime since the previous unclean shutdown:

function tuptime-graceful () {
        local tuptime_since=1
        local temp_array
        while read -r line 
        do
                if [[ "${line}" =~ ' BAD ' ]]
                then
                        read -r -a temp_array <<< "${line}"
                        tuptime_since=$(( temp_array[0] + 1 ))
                        break
                fi
        done < <(tuptime --table --order e --reverse)
        tuptime --since "${tuptime_since}"
}

Ampersand in ipxe script

Example is from a Debian preseed environment where preseed/late_command downloads and executes a shell script

set amp &
set latecmd in-target wget ${script_url} ${amp}${amp} in-target bash script.sh
kernel [...] preseed/late_command="${latecmd}"
Too Good To, UNIX & Linux

Too good to #0003

Linux uptime in seconds, once and for all

awk '{printf "%i\n", $1}' /proc/uptime

“Sudo on demand”, re-exec shell script with sudo if not running as root

#!/usr/bin/env bash
printf "Running as: %s\n" "$(id -un)"
[[ ${EUID} -ne 0 ]] && printf "Re-executing with sudo.\n" && exec sudo "${0}"

See also TGT0006, this is just as useful for downgrading privileges on the fly.

“When was the last time apt-get on that Debian/Ubuntu machine installed package upgrades?”

  • Reliably answering this is a lot harder than it looks, subject of countless discussions and really does need to parse /var/log/apt/history.log, which is painful.
  • The script below maintains a file /var/log/apt/lastupgrade with the last upgrade’s time stamp, for further processing.
  • Does NOT track invocations of apt-get upgrade that did not lead to package upgrades.
  • Does NOT look behind logfile rotations, which should not be a problem because it’s closely hooked to dpkg.

/usr/sbin/apt-lastupgrade:

#!/bin/bash

while IFS=: read -r key value
do
	if [[ "${key}" == 'Start-Date' ]]
	then
		upgraded=0
	elif [[ "${key}" == 'Upgrade' ]]
	then
		upgraded=1
	elif [[ "${key}" == 'End-Date' ]]
	then
		if [[ ${upgraded} -eq 1 ]]
		then
			printf -v lastupgrade "%s" "${value}"
		fi
		upgraded=0
	fi
done < /var/log/apt/history.log

if [[ -v lastupgrade ]]
then
	tee /var/log/apt/lastupgrade <<-Here
	# Timestamp of last upgrade: ${lastupgrade}
	Here
	touch -d "${lastupgrade}" /var/log/apt/lastupgrade
fi

/etc/apt/apt.conf.d/90lastupgrade:

DPkg::Post-Invoke {"/usr/bin/systemd-run --on-active=60 /usr/sbin/apt-lastupgrade || /bin/true"};

Path of running shell script, dirname for locating config files, includes etc.

me_path="$(readlink -f "${0}")"
me_dir="$(dirname "${me_path}")"
me_base="$(basename "${me_path}")"