#inittab

當 Daemon 死掉時自動重新跑起…

以前確保 daemon 掛掉時會重新跑起來大概有幾個方式，像是用 Monit 顧，然後再用 /etc/inittab 確保 Monit 不會掛掉…

在 systemd 的年代，因為 systemd 已經被保護起來，而重跑這個功能在 systemd 裡就有支援，不需要用 Monit 這類程式了。

在 manual 裡搜尋 restart 可以看到幾個參數：

Restart=

RestartForceExitStatus=

RestartPreventExitStatus=

RestartSec=

這次是遇到 SmokePing 的 FastCGI daemon 每隔幾天會自己死掉，導致 nginx 丟出 503 然後被 UptimeRobot 偵測到而拋出警告。

但這個問題只有在一台伺服器會發生，而 log 裡也沒翻到可以繼續 debug 的錯誤訊息，試著猜測一些情境去搜尋引擎找也沒翻到……

Have trouble connecting UART to raspi, symptoms could be nothing displayed on screen, no prompt on login or hanging of screen after connecting.

Causes -

1.Nothing displayed on screen - logging could be disabled in boot cmdline

Fix - 

In /boot/cmdline.txt check if text is

dwc_otg.lpm_enable=0 console=ttyAMA0,115200 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

2.No prompt on boot - getty respawn disabled

Fix - sudo vim /etc/inittab

Check for T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

your serial terminal is usually ttyAMA0 and the corresponding line could vary depending on your baud rate (mine is 115200)

If this line is commented witha  #, remove the #.

3.You can login through UART but session hangs in between - Someother process could be hijacking your UART and writing to ttyAMA0.

Answer: Using inittab to ensure sshd (and other important items) are still running — any drawbacks? #programming #dev #development

Using inittab to ensure sshd (and other important items) are still running any drawbacks?

Having managed to kill sshd on a remote machine (by running a script which used all available memory in the machine, oops…) which I have no access to other than visiting the hosting for[1], I was considering ways to ensure that sshd is always kept running.

Other than a hacky cron job to restart sshd every n…