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Ubuntu Server 22.04系统彻底删除snap组件

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最近在阿里轻量云买了一些机器, 同样都是1C/0.5G, Ubuntu 20.04 的机器运行非常正常, Ubuntu 22.04 的机器却隔一段时间就没有响应了. 具体表现为能ping通, 但是ssh登录会超时失败, 宿主机监控CPU/磁盘IO大涨. 登录VNC能看到类似这样的提示:

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[44211.553196] Out of memory: Killed process 95466(apt-check) ... shmem-rss:0KB, UID:0 pgtables:300KB dom_score_adj:0
[44213.738115] systemd[1]: Failed to start Refresh fwupd metadata and update motd.
[63358.618014] Out of memory: Killed process 123118(apt-check) total-vm:190376KB ... UID:0 pgtables:364kB oom_score_adj:0
[63359.212458] systemd[1] : Failed to start Dailyapt download activities.
[74055.581349] Out of memory: Killed process 126756 (apt-check) total-vm:190376kB, ... UID:0 pgtables:376kB oom_score_adj:0
[121996.542525] Out of memory: Killed process 210249 (apt-check) total-vm:100788kB, ... UID:0 pgtables:228kB oom_score_adj:0
[121996.882131] systemd[1]: snapd.service: Watchdogtimeout (limit 5min)
[121997.311208] systemd[1]: Failed to start Dailyapt download activities.
[179235.303036] Out of memory: Killed process 292938(apt-check) total-vm:190376KB, ... UID:0 pgtables:372kB oom_score_adj:0

而这台机器已经关闭了apt自动更新, 一番搜索之后发现snapd可能会引起这个问题:

  1. snap list
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Name    Version        Rev    Tracking       Publisher   Notes
core20  20240416       2318   latest/stable  canonical✓  base
lxd     5.0.3-80aeff7  29351  5.0/stable/…   canonical✓  -
snapd   2.63           21759  latest/stable  canonical✓  snapd
  1. 删除snap各个包(有依赖关系)
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sudo snap remove --purge lxd
sudo snap remove --purge core20
sudo snap remove --purge snapd
  1. 删除snap
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sudo apt remove snapd
sudo apt purge snapd
  1. 添加apt配置文件防止snapd重新被安装回来

sudo vim /etc/apt/preferences.d/nosnap.pref

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Package: snapd
Pin: release a=*
Pin-Priority: -10
  1. 清除apt缓存, 重新更新一下(可选)

sudo apt clean && sudo apt update

在完全删除掉snapd之后, 目前机器已经正常运行了两三天…

后续

后来发现还是不太行, 解决方案是给这个内存超级小的机器加上Swap. 因为阿里云没创建swap, 而且还把swappiness设置成了0! 为防止奇怪的事情发生, 弄成crontab脚本每分钟跑一下好了.

创建并启用swap

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dd if=/dev/zero of=/swap.img bs=1M count=1024
chmod 600 /swap.img
mkswap /swap.img
swapon /swap.img
````

添加分钟级任务 `sudo crontab -e`

@reboot swapon -s | grep -q swap || swapon /swap.img
@reboot echo 60 > /proc/sys/vm/swappiness

          • swapon -s | grep -q swap || swapon /swap.img
          • echo 60 > /proc/sys/vm/swappiness

### 参考

[Terminate unattended-upgrades or whatever is using apt in ubuntu 18.04 or later editions](https://askubuntu.com/questions/1186492/terminate-unattended-upgrades-or-whatever-is-using-apt-in-ubuntu-18-04-or-later)

[How to Remove Snap Packages in Ubuntu Linux](https://www.debugpoint.com/remove-snap-ubuntu/)

[How do I configure swappiness?](https://askubuntu.com/questions/103915/how-do-i-configure-swappiness)

[How to read oom-killer syslog messages?](https://serverfault.com/questions/548736/how-to-read-oom-killer-syslog-messages)

[How can I check if swap is active from the command line?](https://unix.stackexchange.com/questions/23072/how-can-i-check-if-swap-is-active-from-the-command-line)

[Linux Partition HOWTO: 9. Setting Up Swap Space](https://tldp.org/HOWTO/Partition/setting_up_swap.html)

[How to Clear RAM Memory Cache, Buffer and Swap Space on Linux](https://www.tecmint.com/clear-ram-memory-cache-buffer-and-swap-space-on-linux/)

[Swappiness: What it Is, How it Works & How to Adjust](https://phoenixnap.com/kb/swappiness)