How to find out when a Linux machine was booted via SCP

Why it doesn't work

When you attempt to change the modification time of a file with touch, or more generally with the underlying system call utime, there are two cases.

• You are attempting to set the file's modification time to a specific time. This requires that you are the owner of the file. (Technically speaking, the process's effective user ID must be the owner of the file.²)
• You are attempting to set the file's modification time to the current time. This works if and only if you have permission to write to the file. The reason for this exception is that you could achieve the same effect anyway by overwriting an existing byte of the file with the same value¹.

Why this typically doesn't matter

• When you copy files with ftp, scp, rsync, etc., the copy creates a new file that's owned by whoever did the copy. So the copier has the permission to set the file's times.
• With rsync, you won't be able to set the time of existing directories: they'll be set to the time when a file was last synchronized in them. In most cases, this doesn't matter. You can tell rsync not to bother with directory times by passing --omit-dir-times (-O).
• With version control systems, revision dates are stored inside files; the metadata on the files is mostly irrelevant.

Solutions

This all has to do with enabling PHP development in a single-developer scenario (ie: without SCM).

Ok, stop right there. Just because there's a single developer doesn't mean you shouldn't use SCM. You should be using SCM. Have the developer check in a file, and give him a way to press a “deploy” button to check out the files from SCM into the live directory.

There is absolutely no technical reason why you shouldn't be using SCM, but there may be a human reason. If the person working on these files styles himself “developer”, he should be using SCM. But if this is a non-technical person pushing documents in, SCM might be too complicated. So go on pushing the files over FTP or SSH. There are three ways this can work.

• Do you really need to synchronize times? As indicated above, rsync has an option to not synchronize times. Scp doesn't unless you tell it to. I don't know WinSCP but it probably can too.
• Continue doing what you're doing, just ignore messages about times. The files are still being copied. This isn't a good option, because ignoring errors is always risky. But it is technically possible.
• If you need flexibility in populating the files owned by the apache user, then the usual approach would be to allow the user SSH access as apache. The easy approach is to have the user create an SSH private key and add the corresponding public key to ~apache/.ssh/authorized_keys. This means the user will be able to run arbitrary commands as the apache user. Since you're ok with giving the user sudo rights anyway, it doesn't matter in your case. It's possible, but not so easy, to put more restrictions (you need a separate user database entry with a different name, the same user ID, a restricted shell and a chroot jail; details in a separate question, though this may already be covered on this site or on Server Fault).

¹ _{Or, for an empty file, write a byte and then truncate.}
² _{Barring additional complications, but none that I know of applies here.}

You should make part or all of your .bashrc not run when your shell is non-interactive. (An scp is an example of a non-interactive shell invocation, unless someone has radically altered your systems.) Then put all commands that can possibly generate output in that section of the file.

A standard way to do this in an init file is:

# Put all the commands here that should run regardless of whether
# this is an interactive or non-interactive shell.

# Example command:
umask 0027

# test if the prompt var is not set
if [ -z "$PS1" ]; then
    # prompt var is not set, so this is *not* an interactive shell
    return
fi

# If we reach this line of code, then the prompt var is set, so
# this is an interactive shell.

# Put all the commands here that should run only if this is an
# interactive shell.

# Example command:
echo "Welcome, ${USER}.  This is the ~/.bashrc file."

You might also see people use

[ -z "$PS1" ] && return

instead of my more verbose if statement.

If you don't want to rearrange your whole file, you can also just make certain lines run only in interactive context by wrapping them like so:

if [ -n "$PS1" ]; then
    echo "This line only runs in interactive mode."
fi

If you segregate your .bashrc this way, then your scp commands should no longer have this problem.