Visit Our UNIX and Linux User Community

Linux and UNIX Man Pages

Test Your Knowledge in Computers #80
Difficulty: Easy
Many operating systems today, including Android, Chrome OS, Steam OS, and myriad embedded systems for devices, are based on Linux.
True or False?
Linux & Unix Commands - Search Man Pages

sync(8) [freebsd man page]

SYNC(8) 						    BSD System Manager's Manual 						   SYNC(8)

NAME
sync -- force completion of pending disk writes (flush cache) SYNOPSIS
sync DESCRIPTION
The sync utility can be called to ensure that all disk writes have been completed before the processor is halted in a way not suitably done by reboot(8) or halt(8). Generally, it is preferable to use reboot(8) or halt(8) to shut down the system, as they may perform additional actions such as resynchronizing the hardware clock and flushing internal caches before performing a final sync. The sync utility utilizes the sync(2) function call. SEE ALSO
fsync(2), sync(2), syncer(4), halt(8), reboot(8) HISTORY
A sync utility appeared in Version 4 AT&T UNIX. BSD
May 31, 1993 BSD

Check Out this Related Man Page

SYNC(8) 						      System Manager's Manual							   SYNC(8)

NAME
sync - synchronize data on disk with memory SYNOPSYS
sync [--help] [--version] DESCRIPTION
sync writes any data buffered in memory out to disk. This can include (but is not limited to) modified superblocks, modified inodes, and delayed reads and writes. This must be implemented by the kernel; The sync program does nothing but exercise the sync(2) system call. The kernel keeps data in memory to avoid doing (relatively slow) disk reads and writes. This improves performance, but if the computer crashes, data may be lost or the filesystem corrupted as a result. sync ensures that everything in memory is written to disk. sync should be called before the processor is halted in an unusual manner (e.g., before causing a kernel panic when debugging new kernel code). In general, the processor should be halted using the shutdown(8) or reboot(8) or halt(8) commands, which will attempt to put the system in a quiescent state before calling sync(2). (Various implementations of these commands exist; consult your documentation; on some systems one should not call reboot(8) and halt(8) directly.) GNU STANDARD OPTIONS
--help Print a usage message on standard output and exit successfully. --version Print version information on standard output, then exit successfully. -- Terminate option list. ENVIRONMENT
The variables LANG, LC_ALL, LC_CTYPE, and LC_MESSAGES have the usual meaning. CONFORMING TO
POSIX 1003.2 NOTES
On Linux, sync is only guaranteed to schedule the dirty blocks for writing; it can actually take a short time before all the blocks are finally written. The reboot(8) and halt(8) commands take this into account by sleeping for a few seconds after calling sync(2). This page describes sync as found in the fileutils-4.0 package; other versions may differ slightly. Mail corrections and additions to aeb@cwi.nl. Report bugs in the program to fileutils-bugs@gnu.ai.mit.edu. SEE ALSO
sync(2), halt(8), reboot(8), update(8) GNU fileutils 4.0 1998-11 SYNC(8)

15 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

TIME SYNC (NTP)

Is there a utility which offers the ability to utilize NTP to sync time on machine. If so please point to man page or web site (3 Replies)
Discussion started by: SmartJuniorUnix
3 Replies

2. UNIX for Dummies Questions & Answers

How to place restrictions in a directory

I have a directory called sync and the directory path is ftp/exports/sync. What I would like to do is place some documents in sync for external users to view and would like to have access restriction for the sync directory. i.e. login and password. How do I go about doing this in a Unix enviorment.... (3 Replies)
Discussion started by: coburn
3 Replies

3. Linux

HELP PLEASE about Resync and sync interval in linux

Can anyone could tell me what is the meaning of this problem: Last successful check resync is greater than min sync interval (1195785433 > 7200) And what can do to solve this problem. Thank you..Please HElp me! (4 Replies)
Discussion started by: o_m_g
4 Replies

4. UNIX for Advanced & Expert Users

how to sync remote folders without overwriting

Hi, I need to sync 2 remote folders so i setup with rsync which is working very fine. But, there comes another requirement to maintain multiple versions of files on destination (NOT to overwrite the destination file). If there is difference between source file and destination file, it must... (2 Replies)
Discussion started by: prvnrk
2 Replies

5. UNIX for Advanced & Expert Users

Does sync(2) block writes until completed?

Gentle readers, I am trying to observe system behavior on our RHEL 5.2 machines. I notice that, it appears to me, based on random iterations of dd if=/dev/zero of=/var/tmp/bigfile bs=1024 count=20000 ...that if the pdflush is flushing buffers at the time of my write, my write will take... (4 Replies)
Discussion started by: mschwage
4 Replies

6. UNIX for Advanced & Expert Users

identify the unix process performing high disk i/o reads and writes

Guys, Is there any UNIX command that captures the 'Unix process which is performing high disk I/O reads and writes'. can you help me in this? -Swamy (6 Replies)
Discussion started by: avsswamy
6 Replies

7. AIX

how to remove the stale entry without a reboot??

my AIX server used to have scsi disk hdisk4. Now i removed that disk. But still it is still listed in lspv. So how can i remove the stale entry of it ? (6 Replies)
Discussion started by: navadeep
6 Replies

8. Filesystems, Disks and Memory

Corrupted disk on reboot

Could someone please help me. Users were unable to access SCO Server. Attempted to reboot the machine and following error was reported: UX: vxfs mount: ERROR: /dev/dsk/c1b0t3d0s1 is corrupted, needs checking UX: vxfs mount: ERROR: /dev/dsk/c1b0t3d0s2 is corrupted, needs checking etc. ... (4 Replies)
Discussion started by: mandarin
4 Replies

9. Shell Programming and Scripting

Remove directory with exceptions

Hi, I want to remove a directory recursively except the inside directories calles .SYNC (designsync dirs) I am looking for something like: \rm -rf < find . * | grep -v .SYNC The find works ok but I do not know how to redirect it. Please help. Regards, Ziv (3 Replies)
Discussion started by: zivsegal
3 Replies

10. UNIX for Advanced & Expert Users

How to Sync two servers

Hi All, want to sync. two servers , both are having solaris os. If am updating any thing in one server , it will automatically sync. with the other server . Is it possible , if so den how ? (3 Replies)
Discussion started by: natraj005
3 Replies

11. Shell Programming and Scripting

How to copy very large directory trees

I have constant trouble with XCOPY/s for multi-gigabyte transfers. I need a utility like XCOPY/S that remembers where it left off if I reboot. Is there such a utility? How about a free utility (free as in free beer)? How about an md5sum sanity check too? I posted the above query in another... (3 Replies)
Discussion started by: siegfried
3 Replies

12. Red Hat

Best way to sync time on a Linux machine

I wanted to know which should be the best way to sync time for a linux machine. We have an application server and a database server, both using RHEL 5.8 as the OS. It is important that the time on both these servers match together and also sync with a common time source. As per my knowledge, these... (11 Replies)
Discussion started by: RHCE
11 Replies

13. Shell Programming and Scripting

How can we automaitcally sync/copy files from one directoy to another ?

Hi, I would like to achieve below requirement, I have a directory "/mydir" and I want to automatically sync/copy all the content of /mydir directory to "/yourdir" directory all the time. meaning, if some application creates a file in /mydir, it supposed to be copied/available in "/yourdir"... (4 Replies)
Discussion started by: aaron8667
4 Replies

14. Red Hat

How to sync time with bios in rhel7?

Hi All, I deployed the rhel7 server in the bare metal hardware. I want to configure the rhel7 server to sync time with bios. I tired the below commands. Still it did not sync the time with bios. Thanks, Kalai (3 Replies)
Discussion started by: kalpeer
3 Replies

15. Shell Programming and Scripting

System shell nologin script required

Hi Part of our security audit we found that following system account's had shells configured; sync halt shutdown I believe this can be achieved by following commands: chsh -s /sbin/nologin (user) usermod -s /sbin/nologin (user) However, I would like simple script to... (5 Replies)
Discussion started by: Gamma
5 Replies

Featured Tech Videos