Showing posts with label Unix. Show all posts
Showing posts with label Unix. Show all posts

Thursday, November 17, 2022

What does f+++++++++ mean in rsync logs?

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Let's take a look at how rsync works and better understand the cryptic result lines:

1 - A huge advantage of rsync is that after an interruption the next time it continues smoothly.

The next rsync invocation will not transfer the files again, that it had already transferred, if they were not changed in the meantime. But it will start checking all the files again from the beginning to find out, as it is not aware that it had been interrupted.

2 - Each character is a code that can be translated if you read the section for -i, --itemize-changes in man rsync

Decoding your example log file from the question:

>f.st......

> - the item is received
f - it is a regular file
s - the file size is different
t - the time stamp is different

.d..t......

. - the item is not being updated (though it might have attributes 
    that are being modified)
d - it is a directory
t - the time stamp is different

>f+++++++++

> - the item is received
f - a regular file
+++++++++ - this is a newly created item

The relevant part of the rsync man page:

-i, --itemize-changes

Requests a simple itemized list of the changes that are being made to each file, including attribute changes. This is exactly the same as specifying --out-format='%i %n%L'. If you repeat the option, unchanged files will also be output, but only if the receiving rsync is at least version 2.6.7 (you can use -vv with older versions of rsync, but that also turns on the output of other verbose messages).

The "%i" escape has a cryptic output that is 11 letters long. The general format is like the string YXcstpoguax, where Y is replaced by the type of update being done, X is replaced by the file-type, and the other letters represent attributes that may be output if they are being modified.

The update types that replace the Y are as follows:

  • < means that a file is being transferred to the remote host (sent).
  • > means that a file is being transferred to the local host (received).
  • c means that a local change/creation is occurring for the item (such as the creation of a directory or the changing of a symlink, etc.).
  • h means that the item is a hard link to another item (requires --hard-links).
  • . means that the item is not being updated (though it might have attributes that are being modified).
  • * means that the rest of the itemized-output area contains a message (e.g. "deleting").

The file-types that replace the X are: f for a file, a d for a directory, an L for a symlink, a D for a device, and a S for a special file (e.g. named sockets and fifos).

The other letters in the string above are the actual letters that will be output if the associated attribute for the item is being updated or a "." for no change. Three exceptions to this are: (1) a newly created item replaces each letter with a "+", (2) an identical item replaces the dots with spaces, and (3) an unknown attribute replaces each letter with a "?" (this can happen when talking to an older rsync).

The attribute that is associated with each letter is as follows:

  • c means either that a regular file has a different checksum (requires --checksum) or that a symlink, device, or special file has a changed value. Note that if you are sending files to an rsync prior to 3.0.1, this change flag will be present only for checksum-differing regular files.
  • s means the size of a regular file is different and will be updated by the file transfer.
  • t means the modification time is different and is being updated to the sender’s value (requires --times). An alternate value of T means that the modification time will be set to the transfer time, which happens when a file/symlink/device is updated without --times and when a symlink is changed and the receiver can’t set its time. (Note: when using an rsync 3.0.0 client, you might see the s flag combined with t instead of the proper T flag for this time-setting failure.)
  • p means the permissions are different and are being updated to the sender’s value (requires --perms).
  • An o means the owner is different and is being updated to the sender’s value (requires --owner and super-user privileges).
  • g means the group is different and is being updated to the sender’s value (requires --group and the authority to set the group).
  • The u slot is reserved for future use.
  • The a means that the ACL information changed.
  • The x means that the extended attribute information changed.

One other output is possible: when deleting files, the "%i" will output the string "*deleting" for each item that is being removed (assuming that you are talking to a recent enough rsync that it logs deletions instead of outputting them as a verbose message).



https://stackoverflow.com/questions/4493525/what-does-f-mean-in-rsync-logs 

Saturday, June 12, 2021

10 Screen Command Examples to Manage Linux Terminals

 Screen is a full-screen software program that can be used to multiplexes a physical console between several processes (typically interactive shells). It offers a user to open several separate terminal instances inside a one single terminal window manager.

The screen application is very useful, if you are dealing with multiple programs from a command line interface and for separating programs from the terminal shell. It also allows you to share your sessions with others users and detach/attach terminal sessions.

Screen Command Examples

On my Ubuntu 10.04 Server Edition, Screen has been installed by default. But, in Linux Mint does not have screen installed by default, I need to install it first using apt-get command before using it. Please follow your distribution installation procedure to install screen.

# apt-get install screen (On Debian based Systems)
# yum install screen (On RedHat based Systems)

Actually, Screen is a very good command in Linux which is hidden inside hundreds of Linux commands. Let’s start to see the function of Screen.

Start screen for the first time

Just type screen at the command prompt. Then the screen will show with interface exactly as the command prompt.

pungki@mint ~ $ screen

Show screen parameter

When you enter the screen, you can do all your work as you are in the normal CLI environment. But since the screen is an application, so it have command or parameters.

Type “Ctrl-A” and “?” without quotes. Then you will see all commands or parameters on screen.

                                                             Screen key bindings, page 1 of 1.

                                                             Command key:  ^A   Literal ^A:  a

  break       ^B b         flow        ^F f         lockscreen  ^X x         pow_break   B            screen      ^C c         width       W
  clear       C            focus       ^I           log         H            pow_detach  D            select      '            windows     ^W w
  colon       :            hardcopy    h            login       L            prev        ^H ^P p ^?   silence     _            wrap        ^R r
  copy        ^[ [         help        ?            meta        a            quit        \            split       S            writebuf    >
  detach      ^D d         history     { }          monitor     M            readbuf     <            suspend     ^Z z         xoff        ^S s
  digraph     ^V           info        i            next        ^@ ^N sp n   redisplay   ^L l         time        ^T t         xon         ^Q q
  displays    *            kill        K k          number      N            remove      X            title       A
  dumptermcap .            lastmsg     ^M m         only        Q            removebuf   =            vbell       ^G
  fit         F            license     ,            other       ^A           reset       Z            version     v

^]  paste .
"   windowlist -b
-   select -
0   select 0
1   select 1
2   select 2
3   select 3
4   select 4
5   select 5
6   select 6
7   select 7
8   select 8
9   select 9
I   login on
O   login off
]   paste .

To get out of the help screen, you can press “space-bar” button or “Enter“. (Please note that all shortcuts which use “Ctrl-A” is done without quotes).

Detach the screen

One of the advantages of screen that is you can detach it. Then, you can restore it without losing anything you have done on the screen. Here’s the sample scenario:

You are in the middle of SSH-on your server. Let’s say that you are downloading 400MB patch for your system using wget command.

The download process is estimated to take 2 hours long. If you disconnect the SSH session, or suddenly the connection lost by accident, then the download process will stop. You have to start from the beginning again. To avoid that, we can use screen and detach it.

Take a look at this command. First, you have to enter the screen.

pungki@mint ~ $ screen

Then you can do the download process. For examples on my Linux Mint, I am upgrading my dpkg package using apt-get command.

pungki@mint ~ $ sudo apt-get install dpkg
Sample Output
Reading package lists... Done
Building dependency tree      
Reading state information... Done
The following packages will be upgraded:
  dpkg
1 upgraded, 0 newly installed, 0 to remove and 1146 not upgraded.
Need to get 2,583 kB of archives.
After this operation, 127 kB of additional disk space will be used.
Get:1 http://debian.linuxmint.com/latest/ testing/main dpkg i386 1.16.10 [2,583 kB]
47% [1 dpkg 1,625 kB/2,583 kB 47%]                                        14,7 kB/s

While downloading in progress, you can press “Ctrl-A” and “d“. You will not see anything when you press those buttons. The output will be like this:

[detached from 5561.pts-0.mint]
pungki@mint ~ $

Re-attach the screen

After you detach the screen, let say you are disconnecting your SSH session and going home. In your home, you start to SSH again to your server and you want to see the progress of your download process. To do that, you need to restore the screen. You can run this command:

pungki@mint ~ $ screen -r

And you will see that the process you left is still running.

When you have more than 1 screen session, you need to type the screen session ID. Use screen -ls to see how many screen are available.

pungki@mint ~ $ screen -ls
Sample Output
pungki@mint ~ $ screen -ls
There are screens on:
        7849.pts-0.mint (10/06/2013 01:50:45 PM)        (Detached)
        5561.pts-0.mint (10/06/2013 11:12:05 AM)        (Detached)
2 Sockets in /var/run/screen/S-pungki

If you want to restore screen 7849.pts-0.mint, then type this command.

pungki@mint ~ $ screen -r 7849

Using Multiple Screen

When you need more than 1 screen to do your job, is it possible? Yes it is. You can run multiple screen window at the same time. There are 2 (two) ways to do it.

First, you can detach the first screen and the run another screen on the real terminal. Second, you do nested screen.

Switching between screens

When you do nested screen, you can switch between screen using command “Ctrl-A” and “n“. It will be move to the next screen. When you need to go to the previous screen, just press “Ctrl-A” and “p“.

To create a new screen window, just press “Ctrl-A” and “c“.

Logging whatever you do

Sometimes it is important to record what you have done while you are in the console. Let say you are a Linux Administrator who manage a lot of Linux servers.

With this screen logging, you don’t need to write down every single command that you have done. To activate screen logging function, just press “Ctrl-A” and “H“. (Please be careful, we use capital ‘H’ letter. Using non capital ‘h’, will only create a screenshot of screen in another file named hardcopy).

At the bottom left of the screen, there will be a notification that tells you like: Creating logfile “screenlog.0“. You will find screenlog.0 file in your home directory.

This feature will append everything you do while you are in the screen window. To close screen to log running activity, press “Ctrl-A” and “H” again.

Another way to activate logging feature, you can add the parameter “-L” when the first time running screen. The command will be like this.

pungki@mint ~ $ screen -L

Lock screen

Screen also have shortcut to lock the screen. You can press “Ctrl-A” and “x” shortcut to lock the screen. This is handy if you want to lock your screen quickly. Here’s a sample output of lock screen after you press the shortcut.

Screen used by Pungki Arianto  on mint.
Password:

You can use your Linux password to unlock it.

Add password to lock screen

For security reason, you may want to put the password to your screen session. A Password will be asked whenever you want to re-attach the screen. This password is different with Lock Screen mechanism above.

To make your screen password protected, you can edit “$HOME/.screenrc” file. If the file doesn’t exist, you can create it manually. The syntax will be like this.

password crypt_password

To create “crypt_password” above, you can use “mkpasswd” command on Linux. Here’s the command with password “pungki123“.

pungki@mint ~ $ mkpasswd pungki123
l2BIBzvIeQNOs

mkpasswd will generate a hash password as shown above. Once you get the hash password, you can copy it into your “.screenrc” file and save it. So the “.screenrc” file will be like this.

password l2BIBzvIeQNOs

Next time you run screen and detach it, password will be asked when you try to re-attach it, as shown below:

pungki@mint ~ $ screen -r 5741
Screen password:

Type your password, which is “pungki123” and the screen will re-attach again.

After you implement this screen password and you press “Ctrl-A” and “x” , then the output will be like this.

Screen used by Pungki Arianto  on mint.
Password:
Screen password:

A Password will be asked to you twice. First password is your Linux password, and the second password is the password that you put in your .screenrc file.

Leaving Screen

There are 2 (two) ways to leaving the screen. First, we are using “Ctrl-A” and “d” to detach the screen. Second, we can use the exit command to terminating screen. You also can use “Ctrl-A” and “K” to kill the screen.

That’s some of screen usage on daily basis. There are still a lot of features inside the screen command. You may see screen man page for more detail.

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