Cheatsheet

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enable Wake on Lan

Add in /etc/network/interfaces

_post-up /usr/sbin/ethtool -s eno1 wol g_

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Process mem usage in Mb

ps aux | awk '{print $6/1024 " MB\t\t" $11}' | sort -n

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remove null from exp results in jq

jq '<expression> | select(.Timestamp != null)

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import CA certificate in a snap (mandatory for bitwarden client)

certutil -d /path/to/snap/.pki/nssdb -A -t "TC,," -n "CA name" -i /path/to/cert

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Banalize template source

test $EUID -eq 0 || { echo "Run this script as root"; exit 1; }

package-cleanup --oldkernels --count=1

logrotate -f /etc/logrotate.conf
rm -f /var/log/*-???????? /var/log/*.gz
rm -f /var/log/dmesg.old
rm -rf /var/log/anaconda

cat /dev/null > /var/log/audit/audit.log
cat /dev/null > /var/log/wtmp
cat /dev/null > /var/log/lastlog
cat /dev/null > /var/log/grubby

rm -rf /etc/ssh/*key*

sed -i 's/HOSTNAME=.*$/HOSTNAME=localhost/g' /etc/sysconfig/network
echo 'localhost' > /etc/hostname

find /etc/sysconfig/network-scripts -name ifcfg-* | while read cfg;do
  sed -i -e '/^HWADDR=/d' -e '/^UUID=/d' -e 's/^IPADDR=/#IPADDR=/g' $cfg
done

rm -f /etc/udev/rules.d/*-persistent-*.rules
rm -f /var/lib/dbus/machine-id
echo "uninitialized" > /etc/matchine-id
rm -f /etc/yum.repo.d/*.repo

yum clean all

rm -f /root/.bash_history

touch /.unconfigured

history -c

*For RHEL, add :*
subscription-manager remove --all
subscription-manager unregister
subscription-manager clean

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find files in date range, copy them to another folder

find -newerct "3 May 2024" ! -newerct "4 May 2024" | xargs cp -t ~/test

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Encrypt/descrypt with openssl

openssl enc -aes-256-cbc -pbkdf2 -pass pass:mypass -in myfile -out encrypted

openssl enc -aes-256-cbc -pbkdf2 -pass pass:mypass -d -in encrypted -out decrypted

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Enable DNSSEC at Scaleway

curl https://api.scaleway.com/domain/v2beta1/domains/mydomain/enable-dnssec \
-X POST \
-H "Content-Type: application/json" \
-H "X-Auth-Token: mytoken" \
-d '{
    "ds_record": {
        "key_id": "2371",
        "algorithm": "ecdsap256sha256",
        "digest": {
            "type": "sha_256",
            "digest": "mydigest"
        }
    }
}'

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Sort processes by swap usage

for file in /proc/*/status; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r

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get memory/swap usage by container id

for id in $(docker ps -a -q); do echo $id && docker inspect $id | grep -P '((Memory)|(PID))'; done