Category: Linux

du -h --max-depth=1

经常用，这里做一个备份

位于/var/log/journal文件夹下面的journal 日志太大，一般系统限制为4GB, 对于一些硬盘比较小的VM就不太友好了

这个是由systemd-journal引起的，我们需要clean it 和limit its growth

Clean Existing Logs

Check current disk usage:

journalctl --disk-usage

Delete logs older than a certain time (e.g., 7 days):

journalctl --vacuum-time=7d

Or limit total size (e.g., 500MB):

journalctl --vacuum-size=500M

Or keep only N logs (e.g., last 10 boots):

journalctl --vacuum-files=10

 

Prevent Logs from Growing Too Large

Edit the persistent journal configuration:

sudo nano /etc/systemd/journald.conf

Look for or add these lines:

SystemMaxUse=500M
SystemKeepFree=100M
SystemMaxFileSize=100M
SystemMaxFiles=10

Then restart systemd-journald:

sudo systemctl restart systemd-journald

 

(Optional) Disable Persistent Journaling

If you don’t need persistent logs across reboots:

sudo rm -rf /var/log/journal
sudo mkdir /run/log/journal
sudo systemctl restart systemd-journald

This means logs will be lost after reboot.

对于我个人来说，我喜欢做如下设置:

journalctl --vacuum-size=200M

然后在/etc/systemd/journald.conf 中设置

SystemMaxUse=200M

SystemMaxFileSize=100M

最后重启journald服务

systemcl restart systemd-journald

Supermicro 进入boot meu，需要在启动的时候按F11.

开机界面显示的按Del，是直接进入Bios

即便是同一个文件夹的压缩文件，如果压缩的时间不一样，那么产生的压缩文件的md5值也是不一样的。

原因有三个:

1 Timestamps in Metadata – Many compression tools store file timestamps (creation, modification, and access times) inside the archive. If you compress the same folder at different times, these timestamps may differ, leading to a different MD5 hash.

2 Compression Algorithm Variations – Some compression tools use different compression settings, even if the same files are inside. Small variations in compression level or metadata can result in a different output file and a different MD5 hash.

3 Order of Files – If the compression tool does not always process files in the same order, the resulting archive may be structured differently, leading to a different MD5 hash.

如果想得到固定的MD5值，可以使用如下的三个方法:

1 Hash Individual Files – Instead of hashing the compressed folder, compute MD5 hashes for each file inside the folder and compare them.
2 Use Deterministic Compression – Some tools (like tar –sort=name with gzip –no-name) help create archives with consistent metadata.
3 Exclude Timestamps – Some formats allow you to omit timestamps (e.g., zip –latest-time).

Debian 的更新速度太快了，现在Debian 10 已经出来了，但是有的software 还没有支持debian 10

需要安装Debian 9 的， 可以从这个页面下载安装Debian 9

https://www.debian.org/releases/stretch/debian-installer/