Securely wipe a disk linux
One-pass overwrite with zeros + verify (use hdparm ATA for NVMe)
shred -vzn 1 /dev/sdb
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Check SMART disk health
smartctl -a /dev/sda | grep -E 'SMART overall|Reallocated|Pending|Uncorrectable'
Benchmark sequential disk IO
dd if=/dev/zero of=/tmp/testfile bs=1M count=1024 conv=fdatasync
Show running containers namespaces
lsns -t net,pid,mnt
Inspect cgroup hierarchy
systemd-cgls
Count lines in all logs
find /var/log -name '*.log' -exec wc -l {} + | sort -rn | head -20