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# Решения
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### 1.
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Напишите .sh скрипт в котором в переменную date присваивается значение текущей даты, в переменную claim - строка "snow is white". После вызова скрипт должен выводить строку, используя переменные date и claim:
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```
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Ср 14 сен 2022 14:50:46 +04: The claim that “snow is white” is true if and only if snow is white.
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```
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Сделайте файл исполняемым для владельца и вызовите указанием полного или относительного пути к нему.
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содержимое скрипта 1.sh
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```
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date=$(date)
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claim='snow is white'
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echo "$date: The claim that \"$claim\" is true if and only if $claim."
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```
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### 2.
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Напишите функцию в скрипте, которая создает каталог, путь к которому передан в качестве первого аргумента и переходит в него. Проверьте работу функции в этом же файле. Работает ли функция за пределами контекста скрипта?
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```bash
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$ cat 2.sh
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mkdir_cd () {
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mkdir -p $1
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cd $1
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echo current dir: $(pwd)
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}
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mkdir_cd $1
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stud@stud15:~$ ./2.sh /tmp/1/2/3/4/5
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current dir: /tmp/1/2/3/4/5
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stud@stud15:~$
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```
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После выполнения скрипта текущая директория не изменилась.
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```bash
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$ mkdir_cd () {
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mkdir -p $1
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cd $1
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echo current dir: $(pwd)
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}
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stud@stud15:~$ mkdir_cd /tmp/a/b/c/d
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current dir: /tmp/a/b/c/d
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stud@stud15:/tmp/a/b/c/d$
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```
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После определения функции и вызова в оболочке изменилась.
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### 3.
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Менее известной, но полезной может быть подстановка дескриптора файла с результатом выполнения команды. `<( CMD )` выполнит `CMD` и поместит вывод во временный файл и заменит `<()` именем этого файла. Это полезно, когда команды ожидают, что значения будут переданы через файл, а не STDIN. Например, `diff <(ls foo) <(ls bar)` покажет различия между файлами в каталогах foo и bar.
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```
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$ diff <(cat buylist) <(cat bought)
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1,3c1,5
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< salad
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< milk
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< bread
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---
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> icecream
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> cheese
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> cake
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> lays
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> beer
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```
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### 4.
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Попробуйте условные выражения в скрипте в if конструкции:
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```bash
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$ cat 4.sh
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if [[ true && true ]]
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then
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echo "True"
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fi
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if [[ true || false ]]
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then
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echo "True"
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fi
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stud@stud15:~$ ./4.sh
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True
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True
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```
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### 5.
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Напишите скрипт, который проходит по всем файлам, переданным в качестве аргументов, и ищет в них строку hello. Перенаправьте grep `STDOUT` и `STDERR` в специальный файл `/dev/null`. Для каждого файла в if создайте файл с содержимым `hello`, если `grep` завершился с ошибкой.
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```bash
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$ cat 5.sh
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for f in $@; do
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grep hello $f 2> /dev/null 1> /dev/null
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if [[ $? -ne 0 ]]
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then
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echo "hello" > $f
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fi
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$ ./5.sh /tmp/one /tmp/two /tmp/three
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/tmp/one has no hello in it. correcting.
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/tmp/two has no hello in it. correcting.
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/tmp/three has no hello in it. correcting.
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$ grep hello /tmp/* 2> /dev/null
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/tmp/one:hello
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/tmp/three:hello
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/tmp/two:hello
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```
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### 6.
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Установите пакет shellcheck и проверьте написанный вами ранее скрипт одноименной командой.
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```bash
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$ shellcheck 5.sh
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In 5.sh line 1:
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for f in $@; do
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^-- SC2148 (error): Tips depend on target shell and yours is unknown. Add a shebang or a 'shell' directive.
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^-- SC2068 (error): Double quote array expansions to avoid re-splitting elements.
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In 5.sh line 2:
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grep hello $f 2> /dev/null 1> /dev/null
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^-- SC2086 (info): Double quote to prevent globbing and word splitting.
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Did you mean:
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grep hello "$f" 2> /dev/null 1> /dev/null
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In 5.sh line 3:
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if [[ $? -ne 0 ]]
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^-- SC2181 (style): Check exit code directly with e.g. 'if ! mycmd;', not indirectly with $?.
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In 5.sh line 5:
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echo $f has no hello in it. correcting.
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^-- SC2086 (info): Double quote to prevent globbing and word splitting.
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Did you mean:
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echo "$f" has no hello in it. correcting.
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In 5.sh line 6:
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echo "hello" > $f
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^-- SC2086 (info): Double quote to prevent globbing and word splitting.
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Did you mean:
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echo "hello" > "$f"
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For more information:
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https://www.shellcheck.net/wiki/SC2068 -- Double quote array expansions to ...
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https://www.shellcheck.net/wiki/SC2148 -- Tips depend on target shell and y...
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https://www.shellcheck.net/wiki/SC2086 -- Double quote to prevent globbing ...
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```
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### 7.
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Напишите скрипт, который выполняет следующий код:
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```bash
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$ cat ./7.sh
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#!/usr/bin/env python
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import sys
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for arg in reversed(sys.argv[1:]):
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print(arg)
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$ ./7.sh 1 2 3 4 5
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5
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4
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3
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2
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1
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```
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### 8.
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Функции выполняются в текущей среде оболочке, тогда как скрипты выполняются в своем собственном процессе.
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Проверьте, что функции могут изменять переменные среды, например, изменить текущий каталог, тогда как скрипт не может. Напишите скрипт, в котором инициализируются две переменные `A` и `B`. Перед одной из них указывается `export `. Выполните скрипт и посмотрите на выдачу команды `env`. Выполните файл командой source (source --help). Какие переменные экспортировались в оболочку?
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```bash
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$ cat 8.sh
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#!/bin/bash
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A=1
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export B=2
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stud@stud15:~$ ./8.sh
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stud@stud15:~$ env | grep -E "^A|B"
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stud@stud15:~$ source ./8.sh
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stud@stud15:~$ env | grep -E "^A|B"
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B=2
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```
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### 9.
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Напишите сценарий bash, который запускает следующий сценарий до тех пор, пока он не завершится аварийно, записывает стандартный вывод и потоки ошибок в файлы и печатает все в конце.
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```bash
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stud@stud15:~$ cat random_bug_script.sh
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#!/usr/bin/env bash
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n=$(( RANDOM % 100 ))
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echo $n
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if [[ n -eq 42 ]]; then
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echo "Something went wrong"
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>&2 echo "The error was using magic numbers"
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exit 1
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fi
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echo "Everything went according to plan"
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stud@stud15:~$ cat repeat_until_error.sh
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#!/bin/bash
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echo "" > output.log
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echo "" > error.log
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i=0
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while true; do
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bash $1 2>> error.log 1>> output.log
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if [[ $? -ne 0 ]]; then
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echo Took "$i" iterations to get an error.
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echo "\noutput.log"
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cat output.log
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echo "\nerror.log"
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cat error.log
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break
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fi
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i=$((i+1))
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done
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stud@stud15:~$ ./repeat_until_error.sh ./random_bug_script.sh
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Took 37 iterations to get an error.
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output.log
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Everything went according to plan
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Something went wrong
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error.log
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The error was using magic numbers
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```
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Бонусный балл, за то, что вы можете сообщить, сколько запусков потребовалось для сбоя сценария.
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```bash
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stud@stud15:~$ cat mean.sh
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#!/bin/bash
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script=$1
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iters=$2
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sum=0
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for i in $(seq $iters)
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do
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failedoniter=$(bash $script | grep 'Took' | awk '{ print $2; }')
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sum=$((sum+failedoniter))
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done
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echo Done $iters trials.
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echo Mean number of steps until error: $(( sum / iters ))
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$ time ./mean.sh "./repeat_until_error.sh ./random_bug_script.sh" 1000
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Done 1000 trials.
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Mean number of steps until error: 99
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real 2m6,924s
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user 1m36,964s
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sys 0m29,409s
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```
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### 10.
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Напишите скрипт, который:
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- создаёт пользователя на двух машинах,
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- кроме домашней директории заводит папку для пользователя в `/ceph/` с нужными правами,
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- создаёт ссылку в домашней директории на директорию в `/ceph/`,
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- ограничивает доступ к домашней папке всем, кроме владельца,
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- генерирует пользователям ключи ed25519, рассылает по машинам и регистрирует ключи для беспарольного перемещения пользователя между машинами.
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Настройка беспарольного перехода для суперпользователя между машинами
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```
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root@stud15:~# cat .ssh/config
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Host w001
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HostName 10.160.179.25
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Host w002
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HostName 10.160.179.55
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root@stud15:~# hostname -i
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10.160.179.25
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root@stud15-v1:~# hostname -i
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10.160.179.55
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root@stud15-v1:~# cat /etc/ssh/sshd_config | grep PermitRootLogin
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PermitRootLogin yes
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root@stud15-v1:~# systemctl restart sshd
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root@stud15:~# ssh-copy-id w002
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/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
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/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
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/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
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root@10.160.179.55's password:
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Number of key(s) added: 1
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Now try logging into the machine, with: "ssh 'w002'"
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and check to make sure that only the key(s) you wanted were added.
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root@stud15-v1:~# cat /etc/ssh/sshd_config | grep PermitRootLogin
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PermitRootLogin prohibit-password
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root@stud15-v1:~# systemctl restart sshd
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root@stud15:~# ssh-copy-id w001
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/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
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The authenticity of host '10.160.179.25 (10.160.179.25)' can't be established.
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ECDSA key fingerprint is SHA256:3K1vZ3p2zlZpJabnqm3ZqwUPkmxxnIHiqYplqRLEku8.
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Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
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/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
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/usr/bin/ssh-copy-id: WARNING: All keys were skipped because they already exist on the remote system.
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(if you think this is a mistake, you may want to use -f option)
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```
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Скрипт
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```bash
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root@stud15:~# cat create_user.sh
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#!/bin/bash
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help() {
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echo "Usage: ./create_user.sh file_with_node_ip_addresses user_name"
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}
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if [[ $# < 2 ]]
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then
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help
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exit
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fi
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nodes=$(cat $1)
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user=$2
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create_user_and_link_command="useradd $user --create-home --shell=/bin/bash --key HOME_MODE=0700; \
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mkdir -p /ceph/$user -m 0700; \
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chown $user:$user /ceph/$user; \
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ln -s /ceph/$user /home/$user/ceph; \
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chown $user:$user --no-dereference /home/$user/ceph"
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mkdir -p /root/users.ssh/$user/
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ssh-keygen -t ed25519 -N "" -f "/root/users.ssh/$user/id_ed25519"
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sed --in-place "s/root/user/" "/root/users.ssh/$user/id_ed25519.pub"
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cat /root/users.ssh/$user/id_ed25519.pub > /root/users.ssh/$user/authorized_keys
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echo "" > /root/users.ssh/$user/known_hosts
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for node in $nodes; do
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ssh-keyscan -H "$node" >> /root/users.ssh/$user/known_hosts
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done
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for node in $nodes; do
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echo "$node" "$create_user_and_link_command"
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ssh "$node" "$create_user_and_link_command"
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scp -r /root/users.ssh/$user/ $node:/home/$user/.ssh
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ssh "$node" "chown -R $user:$user /home/$user/.ssh && chmod 0700 /home/$user/.ssh/"
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done
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root@stud15:~# cat nodes
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10.160.179.25
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10.160.179.55
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```
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Проверка
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```
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root@stud15:~# ./create_user.sh nodes user6
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Generating public/private ed25519 key pair.
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Your identification has been saved in /root/users.ssh/user6/id_ed25519
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Your public key has been saved in /root/users.ssh/user6/id_ed25519.pub
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The key fingerprint is:
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SHA256:FdusRTajDoM/7us/Tyf3VCmu/8kAWjWoYkerUGKggzg root@stud15
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The key's randomart image is:
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+--[ED25519 256]--+
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| . . = |
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|o . . . O.o |
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|Eo o..o.+.+o |
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| .. . o..=oo. . .|
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| . oS+oo . ..|
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| o.+.o o . .|
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| ... ooo .|
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| . ...+oo.|
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| .+o.+o..+.|
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+----[SHA256]-----+
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# 10.160.179.25:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.25:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.25:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.25:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.25:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.55:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.55:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
|
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# 10.160.179.55:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
|
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# 10.160.179.55:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
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# 10.160.179.55:22 SSH-2.0-OpenSSH_8.4p1 Debian-5+deb11u1
|
|
|
10.160.179.25 useradd user6 --create-home --shell=/bin/bash --key HOME_MODE=0700; mkdir -p /ceph/user6 -m 0700; chown user6:user6 /ceph/user6; ln -s /ceph/user6 /home/user6/ceph; chown user6:user6 --no-dereference /home/user6/ceph
|
|
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id_ed25519.pub 100% 93 484.7KB/s 00:00
|
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|
id_ed25519 100% 399 2.8MB/s 00:00
|
|
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authorized_keys 100% 93 746.1KB/s 00:00
|
|
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known_hosts 100% 1957 12.5MB/s 00:00
|
|
|
10.160.179.55 useradd user6 --create-home --shell=/bin/bash --key HOME_MODE=0700; mkdir -p /ceph/user6 -m 0700; chown user6:user6 /ceph/user6; ln -s /ceph/user6 /home/user6/ceph; chown user6:user6 --no-dereference /home/user6/ceph
|
|
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id_ed25519.pub 100% 93 434.1KB/s 00:00
|
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id_ed25519 100% 399 2.4MB/s 00:00
|
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authorized_keys 100% 93 625.8KB/s 00:00
|
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known_hosts 100% 1957 10.4MB/s 00:00
|
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root@stud15:~#
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user6@stud15:~$ ssh 10.160.179.55
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Linux stud15-1v15 5.10.0-17-amd64 #1 SMP Debian 5.10.136-1 (2022-08-13) x86_64
|
|
|
|
|
|
The programs included with the Debian GNU/Linux system are free software;
|
|
|
the exact distribution terms for each program are described in the
|
|
|
individual files in /usr/share/doc/*/copyright.
|
|
|
|
|
|
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
|
|
|
permitted by applicable law.
|
|
|
user6@stud15-1v15:~$ ssh 10.160.179.25
|
|
|
Linux stud15 5.10.0-16-amd64 #1 SMP Debian 5.10.127-1 (2022-06-30) x86_64
|
|
|
|
|
|
The programs included with the Debian GNU/Linux system are free software;
|
|
|
the exact distribution terms for each program are described in the
|
|
|
individual files in /usr/share/doc/*/copyright.
|
|
|
|
|
|
Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
|
|
|
permitted by applicable law.
|
|
|
user6@stud15:~$
|
|
|
|
|
|
|
|
|
root@stud15:~# ls -la /home/user6/
|
|
|
total 28
|
|
|
drwx------ 3 user6 user6 4096 сен 15 11:49 .
|
|
|
drwxr-xr-x 13 root root 4096 сен 15 11:47 ..
|
|
|
-rw------- 1 user6 user6 18 сен 15 11:49 .bash_history
|
|
|
-rw-r--r-- 1 user6 user6 220 мар 27 22:40 .bash_logout
|
|
|
-rw-r--r-- 1 user6 user6 3526 мар 27 22:40 .bashrc
|
|
|
lrwxrwxrwx 1 user6 user6 11 сен 15 11:47 ceph -> /ceph/user6
|
|
|
-rw-r--r-- 1 user6 user6 807 мар 27 22:40 .profile
|
|
|
drwx------ 2 user6 user6 4096 сен 15 11:47 .ssh
|
|
|
root@stud15:~# ls -la /ceph
|
|
|
total 32
|
|
|
drwxr-xr-x 8 root root 4096 сен 15 11:47 .
|
|
|
drwxr-xr-x 21 root root 4096 сен 15 11:12 ..
|
|
|
drwx------ 2 user1 user1 4096 сен 15 11:14 user1
|
|
|
drwx------ 2 user2 user2 4096 сен 15 11:25 user2
|
|
|
drwx------ 2 user3 user3 4096 сен 15 11:38 user3
|
|
|
drwx------ 2 user4 user4 4096 сен 15 11:42 user4
|
|
|
drwx------ 2 user5 user5 4096 сен 15 11:44 user5
|
|
|
drwx------ 2 user6 user6 4096 сен 15 11:47 user6
|
|
|
``` |