Dicas shell

Coletânea de dicas úteis, para uso no shell (bash)

Colorir saída (log)

# ccze - A robust log colorizer 
apt-cache search ccze

# Instalar ccze
apt install ccze

# Exemplo de uso
journalctl -f | ccze

Confirmação ao realizar comando de restart ou shutdown

# molly-guard guard against accidental shutdowns/reboots
apt-cache search molly-guard

# instalar molly-guard
apt install molly-guard

Visualizar mais de uma saída de log

# MultiTail - browse through several files at once 
apt-cache search multitail

# instalar multitail
apt install multitail

# uso
multitail -f /var/log/messages /var/log/secure

Data e hora no histórico linux

Inserir a seguinte linha no arquivo .bashrc no diretório home do usuário

# Inserir a linha no profile caso queira que a opção seja global
export HISTTIMEFORMAT="%d-%m-%y %r "
echo 'export HISTTIMEFORMAT="%d-%m-%y %r " ' >> ~/.bashrc

# Forçar gravação após execução a cada comando
echo ‘PROMPT_COMMAND="history -a"’ >> .bashrc

Executar comando remoto em outra máquina usando sshpass

# Instalar sshpass
apt install sshpass

# Definir usuário e senha
SSH_USER='user'
SSH_PASS='pass'
SSH_IP='192.168.0.100'
SSH_COMMAND='cat /etc/fstab'

# Executar sshpass
sshpass -p "$SSH_PASS" ssh -o StrictHostKeyChecking=no -o ConnectTimeout=5 "$SSH_USER"@"$SSH_IP" "$SSH_COMMAND" > /dev/null 2>&1

Montar diretório remoto usando sshfs

# Instalar sshfs
apt install sshfs

# Realizar montagem
mount -t sshfs user@192.168.100.125:/opt/ /mnt

# Listar diretórios
ls /mnt

Desativar ipv6

# Editar o arquivo
nano /etc/sysctl.conf

# Adicionar as seguintes linhas no arquivo sysctl
# Disable IPv6
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1

# Aplicar configuração
sysctl -p

Listar arquivos com permissões Suid e Sguid:

# Listar arquivos usando find
find /  -path /proc -prune -o -type f \( -perm -4000 -o -perm -2000 \) -exec ls -l {} \;

Monitorar website — Usando cron

# Monitora site example.com a cada 5 min
*/5 * * * * curl -s -o /dev/null -w "%{http_code}" https://example.com | grep -q "200" || echo "$(date): Website Down" >> /path/to/log/website.log

Gerar senhas aleatórias com entropia de 128

# Gerar palavra
pwmake 128

Usar partições separadas para maior segurança

/(root) 
/boot  
/home  
/tmp 
/var

Forçar rotacionamento de logs:

# Realizar checagem manual do logrotate
logrotate -vdf /etc/logrotate.conf

Inicialização do sistema— systemd

# Analisar o tempo de carregamento
systemd-analyze blame

# 

Gerenciamento de logs — journalctl

# Listar serviço por unidade
journalctl -u sshd

# Listar detalhes
journalctl -xe

# Listar arquivos de log do kernel
journalctl -k

# Listar logs em tempo real
journalctl -f

# Listar tamanho do log
journalctl --disk-usage

# Verificar a consistencia dos logs
journalctl --verify

# Sanitizar os logs
journalctl --vacuum-size 10M

Gerenciamento de serviços — systemctl

# Listar todas a unidades
systemctl list-units

# Listar arquivos das unidades e estado do serviço
systemctl list-unit-files

# Listar serviço de uma unidade
systemctl show sshd

# Exibir configuração da unidade
systemctl cat sshd

# Listar dependências
systemctl list-dependencies sshd

# Listar serviços em execução
systemctl list-units --type=service --state=running

# Listar serviços habilitados
systemctl list-unit-files --type=service --state=enabled

# Listar sockets dos serviços
systemctl list-sockets

Montar diretório na memória -Ramdisk

# Criar diretório
mkdir /mnt/ramdisk

# Realizar montagem
mount -t tmpfs -o rw,size=2G tmpfs /mnt/ramdisk

Impedir script de rodar caso já esteja em execução

pidof -o %PPID -x "$(basename "$0")" > /dev/null && { echo "Script is already running"; exit 1; }

Comandos ip

# Adicionar ip na interface
ip address add 192.168.1.100/24 dev eth0

# Deletar ip na interface
ip address del 192.168.1.100/24 dev eth0

# Ativar interface
ip link set eth0 up

# Desativar interface
ip link set eth0 down

# Alterar mtu
ip link set eth0 mtu 1500

# Ativar captura de pacotes
ip link set eth0 promisc on

# Definir rota padrão
ip route add default via 192.168.1.1

# Definir rota estática
ip route add 172.16.0.0/16 via 192.168.1.254

# Definir rota estática escolhendo uma interface
ip route add 192.168.2.0/24 via 192.168.1.1 dev eth0

# Deletar uma rota
ip route del 172.16.0.0/16 via 192.168.1.254

# Exibir rota
ip route show

Remover comentários de arquivos

# Remover linhas com comentários
grep -vE '^(\s*#|\s*$)' arquivo

Verificar o tipo de arquivo

# Verificar o tipo de arquivo
file -b --mime-type arquivo

Enviar mensagem para usuário logado no sistema

# write <usuário> <número do tty>, usar em conjunto com o comando who
write root tty1

Receber alerta sobre algum evento de erro ocorrido no log do sistema

tail -f /var/log/syslog | grep --line-buffered 'ERROR' | while read line; do echo "$line" | mail -s "Syslog Error Alert" admin@example.com; done

Listar arquivos maiores que um tamanho especifico

find / -type f -exec du -h {} + | sort -rh | head -n 10

# Deletar arquivos maiores que 100M
find /tmp/ -type f -size +100M -exec rm -i {} \;

Links de referência:

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https://www.cyberciti.biz/tips/linux-security.html

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