bash rematch结合chroot在Plesk虚拟主机无输出问题求助

Hey Simon, let's break down why your setup works on your root server but fails in Plesk, and how to apply the absolute path requirement your provider mentioned.

First, let's get the core issue straight: Plesk's virtual host chroot environments are heavily restricted. They often have a stripped-down PATH variable, and system commands might live in non-standard locations compared to your full root server. When you run chroot without specifying absolute paths, bash can't find the commands it needs, leading to that silent exit you're seeing.

Here's how to fix this step by step:

1. Find Absolute Paths for Commands in the Chroot Environment #

First, you need to know where bash and any other tools you're using (like grep, sed, etc.) live inside the Plesk chroot. There are two reliable ways to do this:

• If you can access the chroot directory from the host system (usually something like /var/www/vhosts/your-domain.com/chroot/), list the contents to confirm paths:

  ls /var/www/vhosts/your-domain.com/chroot/bin/bash
  ls /var/www/vhosts/your-domain.com/chroot/usr/bin/grep
  

• Or, manually enter the chroot to test (if your provider allows it):

  chroot /path/to/plesk-chroot /bin/bash
  # Once inside, run these to get exact paths
  which bash
  which grep
  

Jot down these paths—you'll need them for your script.

2. Update Chroot Calls to Use Absolute Paths for Bash #

When you invoke chroot in your script, you need to specify the absolute path to bash inside the chroot (not the host system's bash). For example:

Bad (relies on PATH, which fails in Plesk): #

chroot /path/to/chroot bash -c '[[ "$my_var" =~ ^[0-9]+$ ]] && echo "Match!"'

Good (uses absolute path to chroot's bash): #

chroot /path/to/chroot /bin/bash -c '[[ "$my_var" =~ ^[0-9]+$ ]] && echo "Match!"'

Replace /bin/bash with the actual path you found in step 1 if it's different (like /usr/local/bin/bash).

3. Use Absolute Paths for External Commands in Your Rematch Logic #

If your script uses external tools (like grep, sed) alongside bash's built-in =~ rematch, you need to replace those with their absolute paths inside the chroot. For example:

Bad (uses relative grep): #

chroot /path/to/chroot /bin/bash -c '
if [[ "$log_entry" =~ ^ERROR: ]]; then
  grep "critical" /var/log/app.log
fi
'

Good (uses absolute path to chroot's grep): #

chroot /path/to/chroot /bin/bash -c '
if [[ "$log_entry" =~ ^ERROR: ]]; then
  /usr/bin/grep "critical" /var/log/app.log
fi
'

Again, use the exact path you found for grep in step 1.

4. Fix Your Script's Shebang Line #

If your script is meant to run inside the chroot, update its shebang to use the absolute path to bash in the chroot. Instead of:

#!/usr/bin/env bash

Use:

#!/bin/bash

(Or whatever absolute path you found for bash in the chroot.) This avoids relying on env, which might not exist or work correctly in the restricted Plesk environment.

Quick Test to Verify #

Once you've updated your script, test it by running it in the Plesk environment. If it still fails, try running the chroot command manually with verbose output to debug:

chroot /path/to/chroot /bin/bash -vx -c '[[ "$test_var" =~ ^test$ ]] && echo "Success"'

The -vx flags will print each command as it runs, helping you spot any missing paths or hidden errors.

内容的提问来源于stack exchange，提问作者Simon