How will you solve the problem if your colleague deleted /usr/bin/chmod and there is no donor system for downloading? How will you change permissions and file modifications in this system?

I will use /lib/ld-linux-x86-64.so.2 /bin/busybox chmod or a similar command depending on the architecture and the availability of busybox.

If busybox is not available, I will try to use /lib/ld-linux-x86-64.so.2 with another system utility that can change permissions, such as /usr/bin/install.

# Example of using install to change permissions
/lib/ld-linux-x86-64.so.2 /usr/bin/install -m 755 /path/to/file /path/to/file

If /lib/ld-linux-x86-64.so.2 or a similar ld is missing, or the required utility is unavailable, I will consider the following options:

1. Using other utilities with built-in functionality: Some programs can change access rights as part of their operation (e.g., some archiving utilities during extraction). This is unlikely for files already in the system but may be useful in specific scenarios.
2. Shell scripts (bash, sh) if a shell is available: Some basic file operations, including possibly changing permission bits, can be indirectly accessed through kernel calls, but this is a very low-level and complex approach dependent on available utilities in the shell. It is highly unlikely that bash alone can change permissions without external utilities.
3. Reboot into recovery mode or with a LiveCD/LiveUSB: This is the most reliable way to restore chmod or directly change permissions by mounting the root filesystem in another environment.
4. Using perl or python if available: If scripting language interpreters are accessible, they often have built-in functions for filesystem operations, including changing permissions.

# Example using Python
import os

try:
    os.chmod('/path/to/file', 0o755)
    print("Permissions changed")
except Exception as e:
    print(f"Error: {e}")

# Example using Perl
#!/usr/bin/perl
chmod(0755, "/path/to/file") or die "Cannot change permissions: $!";
print "Permissions changed\n";

The priority of actions will depend on which utilities and interpreters are available in the system. I will first check for busybox, then other system binaries, and if unsuccessful, I will resort to LiveCD/Recovery Mode as the most reliable solution.