Linux System Administration Questions

pmap -x 1234 | sort -k3 -n

grep -A1 -E "Rss:|Pss:|Private_Clean:|Private_Dirty:" /proc/1234/smaps

valgrind --leak-check=full --show-leak-kinds=all --track-origins=yes ./service

valgrind --tool=massif ./service
ms_print massif.out.<pid>

import tracemalloc
tracemalloc.start()
# capture snapshot periodically
s1 = tracemalloc.take_snapshot()
# later:
s2 = tracemalloc.take_snapshot()
print(s2.compare_to(s1,'lineno')[:20])

fio --name=randwrite --ioengine=libaio --direct=1 --rw=randwrite --bs=4k \
  --iodepth=32 --numjobs=4 --runtime=300 --time_based --group_reporting \
  --filename=/dev/mapper/pgdata

#!/bin/sh
# /usr/local/bin/rotate_logs.sh
# POSIX sh script to rotate logs in a given directory
# Usage: rotate_logs.sh /path/to/logdir

LOGFILE=/var/log/rotate_custom.log
LOCKDIR=/var/lock/rotate_logs.lock
KEEP=7

timestamp() { printf '%s\n' "$(date '+%Y-%m-%d %H:%M:%S')"; }
log() { timestamp | awk '{printf "[%s] ", $0}'; printf '%s\n' "$1" >> "$LOGFILE" 2>/dev/null; }

if [ $# -ne 1 ]; then
  printf 'Usage: %s /path/to/logdir\n' "$0" >&2
  exit 2
fi

LOGDIR=$1

# Basic validations
if [ ! -d "$LOGDIR" ]; then
  log "ERROR: log directory not found: $LOGDIR"
  exit 2
fi

if [ ! -w "$LOGDIR" ]; then
  log "ERROR: no write permission on: $LOGDIR"
  exit 2
fi

# Acquire lock atomically
if mkdir "$LOCKDIR" 2>/dev/null; then
  # Ensure lock removed on exit
  trap 'rmdir "$LOCKDIR" 2>/dev/null; exit' INT TERM EXIT
else
  log "Another rotation is running; exiting."
  exit 0
fi

log "Starting rotation for $LOGDIR"

# Compress files older than 1 day (mtime +0) that are not already .gz
find "$LOGDIR" -type f ! -name '*.gz' -mtime +0 -print0 |
while IFS= read -r -d '' file; do
  if gzip --best -- "$file" 2>/dev/null; then
    log "Compressed: $file"
  else
    log "ERROR compressing: $file"
  fi
done

# Remove old archives, keep last $KEEP by modification time
# Only consider .gz in LOGDIR (not recursively)
set -- $(ls -1t "$LOGDIR"/*.gz 2>/dev/null)
if [ $# -gt "$KEEP" ]; then
  # build list of files to remove: from (KEEP+1)th to end
  i=0
  for f in "$LOGDIR"/*.gz; do
    [ -e "$f" ] || break
    i=$((i+1))
    if [ "$i" -gt "$KEEP" ]; then
      if rm -f -- "$f"; then
        log "Removed old archive: $f"
      else
        log "ERROR removing old archive: $f"
      fi
    fi
  done
fi

log "Rotation completed for $LOGDIR"

# Release lock and exit cleanly
rmdir "$LOCKDIR" 2>/dev/null
trap - INT TERM EXIT
exit 0