linux-ops-cheatsheet

# Linux Ops Cheatsheet / Linux 运维速查 System-administration one-liners for Linux hosts. Read-only diagnostics are safe to run as-is. Commands that touch the kernel, the bootloader, or running processes carry explicit DANGER markers and confirmation gates — read them before you paste. ## When to use / 何时使用 - Inspect memory usage (`free`) or disk IO (`iostat`). - Cap the kernel's usable RAM for low-memory testing (`mem=` boot param). - Detach a foreground job to the background so it survives logout (`bg` + `disown`). - Force an unresponsive host to reboot via the SysRq interface — **last resort only**. Do NOT use this skill for algorithm or data-structure design questions; the file name in the upstream corpus was mislabeled "algorithms" but the content is Linux ops. ## Global preconditions / 全局前提 - Distro examples target **Red Hat / Fedora family**. Paths differ on Debian/Ubuntu/SUSE. - Bootloader and SysRq actions require **root** (`sudo` or a root shell). - `iostat` ships in the `sysstat` package (`sudo yum install sysstat` / `sudo dnf install sysstat`). --- ## 1. Memory usage (read-only / 只读) — 查看内存使用情况 No guard needed; this only reads counters. ```bash free -m # show memory usage in MB / 以 MB 为单位查看内存使用情况 ``` Verify: output prints `Mem:` and `Swap:` rows. Add `-h` for human-readable units. --- ## 2. Disk IO statistics (read-only / 只读) — 查看系统的 IO 统计信息 No guard needed; this only samples kernel IO counters. ```bash iostat -k 3 # print in KB, refresh e...