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dazzmos avatar Ubuntu

Custom modt script prevents me from logging in on server. Am I doing something wrong?

ru flag
dazzmos

I am running Ubuntu 22.04 LTS Server on an old computer I have, and I would like to have a custom script be run when I login to print useful information.

I have the script (linked below), placed it in /etc/profile.d/motd.sh so it runs at login, and ran sudo chmod -x /etc/update-motd.d/* so the default Ubuntu motd isn't executed. But upon logging in, it logs me out immediately. (both via SSH and physically) I had to boot into a live USB on the machine to remove my custom script to be able to login on the server again.

Can't find anything wrong with the script either. If I run it on the server it works as intended (screenshot below), but it hangs when executed as motd...

So I have two questions:

  1. How can I make it so the script doesn't prevent me from logging in? What am I doing wrong?

  2. Is it possible to disable the login for just one user? So in case it ever hangs again for the default user, I can just login to a secondary user that has motd disabled? Thereby avoiding the need for physical access to the server.

This is the output of the script:

enter image description here

It works flawlessly if I run it on the server:

This is the content of the script:

#!/bin/bash


# ---::: Colors :::--- 


RED='\e[38;2;212;51;83m'
GREEN='\e[38;5;2m'
ZGREEN='\e[38;2;186;241;221m'
BLUE='\e[38;5;4m'
PINK='\e[38;2;255;175;255m'
LILAC='\e[38;2;218;186;255m'
EOC='\e[0m' # End of color


# ---::: Global Variables :::--- 


arch=$(uname -m)
distribution=$(lsb_release -s -d)
platform=$(uname -o)
kernel=$(uname -r)
lip=$(ip addr show enp2s0f1 | grep 'inet '| awk '{print $2}' | cut -f1 -d'/')
system_uptime=$(uptime -p | cut -d ' ' -f 2-)
cpu=$(</sys/class/thermal/thermal_zone0/temp)
temperature="$(printf %.1f "$(echo "${cpu}" | awk '{print $1 / 1000}')")°C"

processes=`ps -eo user=|sort|uniq -c | awk '{ print $2 " " $1 }'`
process_all=`echo "$processes"| awk {'print $2'} | awk '{ SUM += $1} END { print SUM }'`
process_root=`echo "$processes"| grep root | awk {'print $2'}`
process_user=`echo "$processes"| grep -v root | awk {'print $2'} | awk '{ SUM += $1} END { print SUM }'`

upgradable=$(apt list --upgradable 2> /dev/null | grep -c upgradable)
security_updates=$(apt list --upgradable 2>/dev/null | grep "\-security" | wc -l)

barWidth=20


# ---::: Logic CPU :::--- 


cpuBarContent=""

percent_cpu=$(awk '{u=$2+$4; t=$2+$4+$5; if (NR==1){u1=u; t1=t;} else print ($2+$4-u1) * 100 / (t-t1) " "; }' <(grep -w "cpu" /proc/stat) <(sleep 0.5;grep -w "cpu" /proc/stat))
percent_cpu=$(echo ${percent_cpu%.*})

usedCPUBarWidth=$((($percent_cpu*$barWidth)/100))

# Color when $percent_cpu is 0-49
cpuColor="$ZGREEN"

if [[ "${percent_cpu}" -ge 65 && "${percent_cpu}" -lt 85 ]]; then
  cpuColor="$LILAC"
elif [[ "${percent_cpu}" -ge 85 && "${percent_cpu}" -le 100 ]]; then
  cpuColor="$RED"
fi

for sep in $(seq 1 $usedCPUBarWidth); do
  cpuBarContent="${cpuBarContent}${cpuColor}■$EOC"
done
cpuBarContent="${cpuBarContent}"
for sep in $(seq 1 $(($barWidth-$usedCPUBarWidth))); do
  cpuBarContent="${cpuBarContent}-"
done
cpuBar="[${cpuBarContent}] $percent_cpu%"


# ---::: Logic RAM :::--- 


used_ram=" " read USED <<<$(free -htm | grep "Mem" | awk {'print $3'} | cut -f1 -d'i')
total_ram=" " read TOTAL <<<$(free -htm | grep "Mem" | awk {'print $2'} | cut -f1 -d'i')
percent_ram=$(vmstat -s | awk ' $0 ~ /total memory/ {total=$1 } $0 ~/free memory/ {free=$1} $0 ~/buffer memory/ {buffer=$1} $0 ~/cache/ {cache=$1} END{print (total-free-buffer-cache)/total*100}')
percent_ram=`echo ${percent_ram%.*}`

ramBarContent=""
usedRAMBarWidth=$((($percent_ram*$barWidth)/100))

# Color when $percent_ram is 0-49
ramColor="$ZGREEN" 

if [[ "${percent_ram}" -ge 65 && "${percent_ram}" -lt 85 ]]; then
    ramColor="$LILAC"
elif [[ "${percent_ram}" -ge 85 && "${percent_ram}" -le 100 ]]; then
    ramColor="$RED"
fi

for sep in $(seq 1 $usedRAMBarWidth); do
    ramBarContent="${ramBarContent}${ramColor}■$EOC"
done

ramBarContent="${ramBarContent}"
for sep in $(seq 1 $(($barWidth-$usedRAMBarWidth))); do
    ramBarContent="${ramBarContent}-"
done
ramBar="[${ramBarContent}]"


# ---::: Logic Storage :::--- 


mountpoints=('/')

storage=$(df -h / | grep '/dev/sda2' | awk '{print $3" / "$2" - "}')
storage_percent=$(df -h / | grep '/dev/sda2' | awk '{print $5}')

for point in "${mountpoints[@]}"; do
    line=$(df -h "${point}")
    percent_hd=$(echo "$line"|tail -n1|awk '{print $5;}'|sed 's/%//')
    usedBarWidth=$(((percent_hd*barWidth)/100))
    hdBarContent=""
    # Color when $percent_hd is 0-49
    hdColor="$ZGREEN"

    if [[ "${percent_hd}" -ge 65 && "${percent_hd}" -lt 85 ]]; then
        hdColor="$LILAC"
    elif [[ "${percent_hd}" -ge 85 && "${percent_hd}" -le 100 ]]; then
        hdColor="$RED"
    fi
    
    hdBarContent="${hdCcolor}"
    for sep in $(seq 1 $usedBarWidth); do
        hdBarContent="${hdBarContent}${hdColor}■$EOC"
    done
    hdBarContent="${hdBarContent}"
    for sep in $(seq 1 $(($barWidth-$usedBarWidth))); do
        hdBarContent="${hdBarContent}-"
    done
    hdBar="[${hdBarContent}]"
done


# ---::: Logic Docker Services :::--- 


export LANG='en_US.UTF-8'
# set column width
COLUMNS=2

length=13

mapfile -t containers < <( docker ps --format "{{.Names}} {{.Status}}" -a | awk '{ print $1,$2 }' | sed '/^\s*$/d' | tail -n +1)

IFS=$'\n' containers=($(sort <<<"${containers[*]}"))
unset IFS

serviceCount=`echo ${#containers[@]}`

services=""
for i in "${!containers[@]}"; do
    IFS=" " read serviceName status <<< ${containers[i]}

    # add ... to service name
    count=`echo -n "$serviceName" | wc -c`
    remaining=`expr $length - $count`
    for j in $(seq $remaining); do 
        serviceName+="."
    done
    
    if [[ "${status}" == "Up" ]]; then
        services+=" $PINK-$EOC ${serviceName}: ${GREEN}running$EOC  "
    else
        services+=" $PINK-$EOC ${serviceName}: ${RED}stopped$EOC    "
    fi
    # insert \n every $COLUMNS column
    if [ $((($i+1) % $COLUMNS)) -eq 0 ] && [[ $i+1 -lt $serviceCount ]]; then
        services+="\n"
    fi
done
#services+="\n"

outServices=`echo "$services"`


# ---::: Printed Elements :::--- 


echo -e "╔═══════════════════════════════ஓ๏⊙๏ஓ═════════════════════════════╗
                             WELCOME
╚═══════════════════════════════ஓ๏⊙๏ஓ═════════════════════════════╝

$BLUE===================================================================$EOC
 $PINK-$EOC Local IP.....: ${GREEN}${lip}$EOC
 $PINK-$EOC Processes....: ${GREEN}${process_all}$EOC (total), ${GREEN}${process_user}$EOC (user), ${GREEN}${process_root}$EOC (root)
 $PINK-$EOC Uptime.......: ${GREEN}${system_uptime}$EOC
$BLUE===================================================================$EOC
 $PINK-$EOC CPU usage....: $cpuBar - ${GREEN}${temperature}$EOC      
 $PINK-$EOC RAM used.....: $ramBar $USED / $TOTAL - ${GREEN}$percent_ram%$EOC
 $PINK-$EOC Disk Space...: $hdBar $storage${GREEN}$storage_percent$EOF
$BLUE===================================================================$EOC
$outServices
$BLUE===================================================================$EOC
$distribution ($platform $kernel $arch)"


# check if there are updates available

stamp="/var/lib/update-notifier/updates-available"

[ ! -r "$stamp" ] || cat "$stamp"

find $stamp -newermt 'now-7 days' 2> /dev/null | grep -q -m 1 '.' || /usr/share/update-notifier/notify-updates-outdated


# check if there are firmware updates
 
if [ -f /run/motd.d/85-fwupd ]; then
    cat /run/motd.d/85-fwupd
fi


# Unattended Upgrades

if [ -x /usr/share/unattended-upgrades/update-motd-unattended-upgrades ]; then
    exec /usr/share/unattended-upgrades/update-motd-unattended-upgrades
fi


# check if there are release upgrades

if [ -x /usr/lib/ubuntu-release-upgrader/release-upgrade-motd ]; then
    exec /usr/lib/ubuntu-release-upgrader/release-upgrade-motd
fi


# checks if reboot is required

if [ -x /usr/lib/update-notifier/update-motd-reboot-required ]; then
    exec /usr/lib/update-notifier/update-motd-reboot-required
fi
74
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user535733 avatar
cn flag
user535733
Review your logs to determine why you cannot login. Since you have access to the hardware but cannot login, you might need to use a LiveUSB's "Try Ubuntu" environment to access the logs.
0
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hr flag
steeldriver
At least with the default Ubuntu `/etc/profile`, files in `/etc/profile.d/` are *sourced* rather than simply run - your script is then using `exec`, which *replaces* the current process - i.e. your login shell
1
Reply
Raffa avatar
jp flag
Raffa
... In particular, you're replacing your login shell with a non-shell e.g. `exec /usr/share/unattended-upgrades/update-motd-unattended-upgrades` ... That has similar effect of e.g. `exec /bin/test` which will log you out (*terminate your session*) as well if you are at $SHLVL 1
1
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Raffa avatar
jp flag
Raffa
@steeldriver Your comment looks pretty much like an answer to me and it probably should be.
0
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hr flag
steeldriver
... fundamentally, `/etc/profile.d/` is the wrong place for a dynamic motd script - you already know the right place (`/etc/update-motd.d/`) so I don't understand why you are not using that location?
0
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Raffa avatar
jp flag
Raffa
... *"It works flawlessly if I run it on the server:"* ... That's because you're executing it which will run it in a subshell and the subshell is the one getting replaced by `exec` i.e. a shell one level deep from your current shell ... But try to run it in the current shell instead e.g. with `source scriptfile` and it will log you out.
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dazzmos avatar
ru flag
dazzmos
@steeldriver @Raffa Thanks guys. I have switched `exec` to `sh`, as those are sh scripts. I followed a guide on youtube and it said to put it in profile.d. I will put it in update-motd.d tomorrow and test it all out. Will update here once I do. Thanks for the info!
0
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hr flag
steeldriver
... when you do that, make sure the file name obeys the conventions listed under `BEST PRACTICES` in `man update-motd`
0
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dazzmos avatar
ru flag
dazzmos
@steeldriver Thank you, it worked!
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