Revisions to How can I get back a system file after deleting it from my Mac?

Bounty Ended with 50 reputation awarded by bmike♦

occurred Mar 16, 2014 at 19:11

explain benefits of this and risks - no internet, no reboot, potential version conflicts

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edited Mar 16, 2014 at 19:10

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If you don't mind or are sure your Recovery HD is patched to match the OS on your main system, you can snag a file and see if it works without needing to do a full reinstall of the OS orand without needing to boot into Recovery HD if you are OK modifying the system as it's runninga restart or an internet connection / saved installer.

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

If you are sure your Recovery HD is patched to match the OS on your main system, you can snag a file and see if it works without needing to do a full reinstall of the OS or without needing to boot into Recovery HD if you are OK modifying the system as it's running.

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

If you don't mind or are sure your Recovery HD is patched to match the OS on your main system, you can snag a file and see if it works without needing to do a full reinstall of the OS and without needing a restart or an internet connection / saved installer.

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

added warning to the text. This is more dangerous than a reinstall or a restore from backup or even copying the files when booted from recovery. But it's still a cool answer.

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edited Mar 11, 2014 at 20:39

bmike ♦

241.3k
80
433
958

If you are sure your Recovery HD is patched to match the OS on your main system, you can snag a file and see if it works without needing to do a full reinstall of the OS or without needing to boot into Recovery HD if you are OK modifying the system as it's running.

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

If you are sure your Recovery HD is patched to match the OS on your main system, you can snag a file and see if it works without needing to do a full reinstall of the OS or without needing to boot into Recovery HD if you are OK modifying the system as it's running.

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

deleted 495 characters in body; added 291 characters in body

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edited Mar 10, 2014 at 19:00

grg ♦

205.6k
45
364
495

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Pacifist with OS X install media

If you've got an OS X install media and Pacifist, you can browse the install media and grab the file.

If you have Pacifist but no install media, it will prompt you to download the installer.

No known Apple install packages were found on any inserted disks

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Pacifist with OS X install media

If you've got an OS X install media and Pacifist, you can browse the install media and grab the file.

If you have Pacifist but no install media, it will prompt you to download the installer.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

Use the Recovery partition

Many¹ system files are also included on the Recovery partition and can be copied over.

Mount the Recovery HD
```
 diskutil mount Recovery\ HD
```

Mount the BaseSystem.dmg

 hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg

Copy the file

 FILE="/usr/bin/codesign"
 sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

This process can be combined into a single-line command if you have to run it frequently…

FILE="/usr/bin/codesign"; diskutil mount Recovery\ HD && hdiutil mount /Volumes/Recovery\ HD/com.apple.recovery.boot/BaseSystem.dmg && sudo cp -p /Volumes/OS\ X\ Base\ System/${FILE} ${FILE}

Even if you have deleted the cp binary (which could happen), there is /usr/bin/ditto, /usr/bin/tar and several other commands that can stand in for cp.

Reinstall OS X

If you've got the ability to reinstall OS X through the Recovery HD, Internet Recovery or an OS X install media then reinstalling OS X will 'repair' your install and copy any missing/broken system files back to your system.

I recommend that you do a permissions repair using Disk Utility after copying a file manually and then rebooting. If the fix works, now would be an excellent time for another backup snapshot.

^{¹ Not all system files are on the Recovery HD, but many are. If the copying command doesn't work, check that the file exists on the Recovery HD.}

thin out some of the answers that exist elsewhere. Perhaps making a second answer that people can vote on / scan about copying the files from a trusted source would be good? I'd up vote it :-)

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edited Mar 10, 2014 at 18:49

bmike ♦

241.3k
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433
958

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added 164 characters in body

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edited Feb 3, 2014 at 20:29

bmike ♦

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code formatting

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edited Jan 9, 2014 at 21:44

grg ♦

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Preserve permissions and make the file path clearly distinct from the base system path

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edited Jan 9, 2014 at 21:43

bmike ♦

241.3k
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created Jan 9, 2014 at 21:02

grg ♦

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Use the Recovery partition

Reinstall OS X

Use the Recovery partition

Reinstall OS X

Use the Recovery partition

Reinstall OS X

Use the Recovery partition

Reinstall OS X

Use the Recovery partition

Reinstall OS X

Use the Recovery partition

Reinstall OS X

Use the Recovery partition

Pacifist with OS X install media

Reinstall OS X

Use the Recovery partition

Pacifist with OS X install media

Reinstall OS X

Use the Recovery partition

Reinstall OS X