How do I revert a Git repository to a previous commit

Question

How do I revert from my current state to a snapshot made on a certain commit   If I do git log  then I get the following output     git log commit a867b4af366350be2e7c21b8de9cc6504678a61b  Author  Me  lt me me com gt  Date    Thu Nov 4 18 59 41 2010 -0400  blah blah blah     commit 25eee4caef46ae64aa08e8ab3f988bc917ee1ce4 Author  Me  lt me me com gt  Date    Thu Nov 4 05 13 39 2010 -0400  more blah blah blah     commit 0766c053c0ea2035e90f504928f8df3c9363b8bd Author  Me  lt me me com gt  Date    Thu Nov 4 00 55 06 2010 -0400  And yet more blah blah     commit 0d1d7fc32e5a947fbd92ee598033d85bfc445a50 Author  Me  lt me me com gt  Date    Wed Nov 3 23 56 08 2010 -0400  Yep  more blah blah    How do I revert to the commit from November 3  i e  commit 0d1d7fc

User · Answer

The best option for me and probably others is the Git reset option:

git reset --hard <commidId> && git clean -f

This has been the best option for me! It is simple, fast and effective!

** Note:** As mentioned in comments don't do this if you're sharing your branch with other people who have copies of the old commits

Also from the comments, if you wanted a less 'ballzy' method you could use

git clean -i

User · Answer

After all the changes  when you push all these commands  you might have to use   git push -f       And not only git push

User · Answer

Caution  This command can cause losing commit history  if user put the wrong commit mistakenly  Always have en extra backup of your git some   where else just in case if you do mistakes  than you are a bit safer         I have had a similar issue and wanted to revert back to an earlier commit  In my case I was not interested to keep the newer commit  hence I used Hard   This is how I did it   git reset --hard CommitId  amp  amp  git clean -f   This will revert on the local repository  and here after using git push -f will update the remote repository   git push -f

User · Answer

Before answering let s add some background  explaining what this HEAD is  First of all what is HEAD  HEAD is simply a reference to the current commit  latest  on the current branch  There can only be a single HEAD at any given time  excluding git worktree   The content of HEAD is stored inside  git HEAD  and it contains the 40 bytes SHA-1 of the current commit   detached HEAD If you are not on the latest commit - meaning that HEAD is pointing to a prior commit in history it s called detached HEAD   On the command line it will look like this - SHA-1 instead of the branch name since the HEAD is not pointing to the the tip of the current branch    A few options on how to recover from a detached HEAD   git checkout git checkout  lt commit id gt  git checkout -b  lt new branch gt   lt commit id gt  git checkout HEAD X    x is the number of commits t go back  This will checkout new branch pointing to the desired commit  This command will checkout to a given commit  At this point you can create a branch and start to work from this point on    Checkout a given commit    Doing so will result in a  detached HEAD  which mean that the  HEAD    is not pointing to the latest so you will need to checkout branch   in order to be able to update the code  git checkout  lt commit-id gt     Create a new branch forked to the given commit git checkout -b  lt branch name gt    git reflog You can always use the reflog as well  git reflog  will display any change which updated the HEAD and checking out the desired reflog entry will set the HEAD back to this commit  Every time the HEAD is modified there will be a new entry in the reflog git reflog git checkout HEAD        This will get you back to your desired commit   git reset HEAD --hard  lt commit id gt   quot Move quot  your head back to the desired commit    This will destroy any local modifications    Don t do it if you have uncommitted work you want to keep  git reset --hard 0d1d7fc32    Alternatively  if there s work to keep  git stash git reset --hard 0d1d7fc32 git stash pop   This saves the modifications  then reapplies that patch after resetting    You could get merge conflicts  if you ve modified things which were   changed since the commit you reset to    Note   Since Git 2 7  you can also use the git rebase --no-autostash as well    This schema illustrates which command does what  As you can see there reset  amp  amp  checkout modify the HEAD

User · Answer

For rollback  or to revert    1  git revert --no-commit  commit-code-to-remove  HEAD  e g  git revert --no-commit d57a39d HEAD  2  git commit 3  git push   Try the above two steps  and if you find this is what you want then git push   If you find something wrong  do   git revert --abort

User · Answer

In GitKraken you can do this    Right click on the commit that you want to reset  choose  Reset to this commit Hard    Right click on the commit again  choose  Current branch name Push    Click on the Force Push      Obs   You need to be careful  because all the commit history after the hard reset are lost and this action is irreversible  You need to be sure what you doing

User · Answer

Here is a much simpler way to go back to a previous commit  and have it in an uncommited state  to do with it whatever you like    git reset HEAD 1   So  no need for commit ids and so on

User · Answer

Extra Alternatives to Jefromi s Solutions  Jefromi s solutions are definitely the best ones  and you should definitely use them  However  for the sake of completeness  I also wanted to show these other alternative solutions that can also be used to revert a commit  in the sense that you create a new commit that undoes changes in previous commit  just like what git revert does    To be clear  these alternatives are not the best way to revert commits  Jefromi s solutions are  but I just want to point out that you can also use these other methods to achieve the same thing as git revert   Alternative 1  Hard and Soft Resets  This is a very slightly modified version of Charles Bailey s solution to Revert to a commit by a SHA hash in Git      Reset the index to the desired commit git reset --hard  lt commit gt     Move the branch pointer back to the previous HEAD git reset --soft HEAD  1     Commit the changes git commit -m  Revert to  lt commit gt     This basically works by using the fact that soft resets will leave the state of the previous commit staged in the index staging-area  which you can then commit   Alternative 2  Delete the Current Tree and Replace with the New One  This solution comes from svick s solution to Checkout old commit and make it a new commit   git rm -r   git checkout  lt commit gt    git commit   Similarly to alternative  1  this reproduces the state of  lt commit gt  in the current working copy  It is necessary to do git rm first because git checkout won t remove files that have been added since  lt commit gt

User · Answer

This is one more way to directly reset to a recent commit  git stash git stash clear   It directly clears all the changes that you have been making since the last commit   PS  It has a little problem  it also deletes all you recently stored stash changes  Which I guess in most cases should not matter

User · Answer

Select your required commit  and check it by  git show HEAD git show HEAD 1 git show HEAD 2    till you get the required commit  To make the HEAD point to that  do  git reset --hard HEAD 1   or git reset --hard HEAD 2 or whatever

User · Answer

You can do this by the following two commands   git reset --hard  previous Commit SHA id here  git push origin  branch Name  -f   It will remove your previous Git commit   If you want to keep your changes  you can also use   git reset --soft  previous Commit SHA id here    Then it will save your changes

User · Answer

I believe some people may come to this question wanting to know how to rollback committed changes they ve made in their master - ie throw everything away and go back to origin master  in which case  do this   git reset --hard origin master   https   superuser com questions 273172 how-to-reset-master-to-origin-master

User · Answer

First  get the string that identifies the commit in some date  doing   git rev-list -n 1 --before  2009-07-27 13 37  origin master   It prints the commit identifier  takes the string  for instance XXXX  and does   git checkout XXXX

User · Answer

This depends a lot on what you mean by  quot revert quot   Temporarily switch to a different commit If you want to temporarily go back to it  fool around  then come back to where you are  all you have to do is check out the desired commit    This will detach your HEAD  that is  leave you with no branch checked out  git checkout 0d1d7fc32  Or if you want to make commits while you re there  go ahead and make a new branch while you re at it  git checkout -b old-state 0d1d7fc32  To go back to where you were  just check out the branch you were on again   If you ve made changes  as always when switching branches  you ll have to deal with them as appropriate  You could reset to throw them away  you could stash  checkout  stash pop to take them with you  you could commit them to a branch there if you want a branch there   Hard delete unpublished commits If  on the other hand  you want to really get rid of everything you ve done since then  there are two possibilities  One  if you haven t published any of these commits  simply reset    This will destroy any local modifications    Don t do it if you have uncommitted work you want to keep  git reset --hard 0d1d7fc32    Alternatively  if there s work to keep  git stash git reset --hard 0d1d7fc32 git stash pop   This saves the modifications  then reapplies that patch after resetting    You could get merge conflicts  if you ve modified things which were   changed since the commit you reset to   If you mess up  you ve already thrown away your local changes  but you can at least get back to where you were before by resetting again  Undo published commits with new commits On the other hand  if you ve published the work  you probably don t want to reset the branch  since that s effectively rewriting history  In that case  you could indeed revert the commits  With Git  revert has a very specific meaning  create a commit with the reverse patch to cancel it out  This way you don t rewrite any history    This will create three separate revert commits  git revert a867b4af 25eee4ca 0766c053    It also takes ranges  This will revert the last two commits  git revert HEAD 2  HEAD   Similarly  you can revert a range of commits using commit hashes  non inclusive of first hash   git revert 0d1d7fc  a867b4a    Reverting a merge commit git revert -m 1  lt merge commit sha gt     To get just one  you could use  rebase -i  to squash them afterwards   Or  you could do it manually  be sure to do this at top level of the repo    get your index and work tree into the desired state  without changing HEAD  git checkout 0d1d7fc32      Then commit  Be sure and write a good message describing what you just did git commit  The git-revert manpage actually covers a lot of this in its description  Another useful link is this git-scm com section discussing git-revert  If you decide you didn t want to revert after all  you can revert the revert  as described here  or reset back to before the revert  see the previous section   You may also find this answer helpful in this case  How can I move HEAD back to a previous location   Detached head   amp  Undo commits

User · Answer

If the situation is an urgent one  and you just want to do what the questioner asked in a quick and dirty way  assuming your project is under a directory called  for example   my project      QUICK AND DIRTY  depending on the circumstances  quick and dirty may in fact be very GOOD  What my solution here does is NOT replace irreversibly the files you have in your working directory with files hauled up extracted from the depths of the git repository lurking beneath your  git  directory using fiendishly clever and diabolically powerful git commands  of which there are many  YOU DO NOT HAVE TO DO SUCH DEEP-SEA DIVING TO RECOVER what may appear to be a disastrous situation  and attempting to do so without sufficient expertise may prove fatal      Copy the whole directory and call it something else  like  my project - copy   Assuming your git repository   repo   files are under the  my project  directory  the default place for them  under a directory called   git    you will now have copied both your work files and your repo files  Do this in the directory  my project        my project   git reset --hard  first-4-letters amp numbers-of-commit s-SHA     This will return the state of the repo under  my project  to what it was when you made that commit  a  commit  means a snapshot of your working files   All commits since then will be lost forever under  my project   BUT    they will still be present in the repo under  my project - copy  since you copied all those files - including the ones under      git    You then have two versions on your system    you can examine or copy or modify files of interest  or whatever  from the previous commit  You can completely discard the files under  my project - copy   if you have decided the new work since the restored commit was going nowhere      The obvious thing if you want to carry on with the state of the project without actually discarding the work since this retrieved commit is to rename your directory again  Delete the project containing the retrieved commit  or give it a temporary name  and rename your  my project - copy  directory back to  my project   Then maybe try to understand some of the other answers here  and probably do another commit fairly soon   Git is a brilliant creation but absolutely no-one is able to just  pick it up on the fly   also people who try to explain it far too often assume prior knowledge of other VCS  Version Control Systems  and delve far too deep far too soon  and commit other crimes  like using interchangeable terms for  checking out  - in ways which sometimes appear almost calculated to confuse a beginner     To save yourself much stress  learn from my scars  You have to pretty much have to read a book on Git - I d recommend  Version Control with Git   Do it sooner rather than later  If you do  bear in mind that much of the complexity of Git comes from branching and then remerging  you can skip those parts in any book  From your question there s no reason why people should be blinding you with science     Especially if  for example  this is a desperate situation and you re a newbie with Git   PS  One other thought  It is  now  actually quite simple to keep the Git repo in a directory other than the one with the working files  This would mean you would not have to copy the entire Git repository using the above quick  amp  dirty solution  See the answer by Fryer using --separate-git-dir here  Be warned  though  If you have a  separate-directory  repository which you don t copy  and you do a hard reset  all versions subsequent to the reset commit will be lost forever  unless you have  as you absolutely should  regularly backed up your repository  preferably to the Cloud  e g  Google Drive  among other places   On this subject of  backing up to the Cloud   the next step is to open an account  free of course  with GitHub or  better in my view  GitLab  You can then regularly do a git push command to make your Cloud repo up-to-date  properly   But again  talking about this may be too much too soon

User · Answer

I have tried a lot of ways to revert local changes in Git  and it seems that this works the best if you just want to revert to the latest commit state    git add    amp  amp  git checkout master -f   Short description     It will NOT create any commits as git revert does  It will NOT detach your HEAD like git checkout  lt commithashcode gt  does  It WILL override all your local changes and DELETE all added files since the last commit in the branch  It works only with branches names  so you can revert only to latest commit in the branch this way    I found a much more convenient and simple way to achieve the results above    git add    amp  amp  git reset --hard HEAD   where HEAD points to the latest commit at you current branch   It is the same code code as boulder ruby suggested  but I have added git add   before  git reset --hard HEAD to erase all new files created since the last commit since this is what most people expect I believe when reverting to the latest commit

User · Answer

It can be done much easier with Sourcetree  Just right click commit you are looking for and chose  Checkout  from menu

User · Answer

Idea  You basically want to replace the current working tree state with the one from a previous commit and then create a commit out of it  Ignored files should best be not changed  Here is how   Emtpy the working tree     git rm -r --cached    amp  amp  git clean -f -d   Bring the working tree in the state we want      git checkout 0d1d7fc3     Create the revert commit   git add --all  amp  amp  git commit -m  quot revert to 0d1d7fc3 quot      At first I thought that Yarins answer would be the best  but it doesn t work for merge commits  This solution does  Additionally it does not delete anything  pushed or upushed  from the history  It produces one clean commit which represents the state we want to revert back to     by removing untracked but not ignored files  the ones specified in  gitignore  from working tree  The working tree is empty except for the ignored files which we wanted to keep  if not specifiy -x option for clean     When a path is specified  here      checkout leaves HEAD alone

User · Answer

Revert to most recent commit and ignoring all local changes   git reset --hard HEAD

User · Answer

If you want to  uncommit   erase the last commit message  and put the modified files back in staging  you would use the command   git reset --soft HEAD 1    --soft indicates that the uncommitted files should be retained as working files opposed to --hard which would discard them  HEAD 1 is the last commit   If you want to rollback 3 commits you could use HEAD 3   If you want to rollback to a specific revision number  you could also do that using its SHA hash    This is an extremely useful command in situations where you committed the wrong thing and you want to undo that last commit   Source  http   nakkaya com 2009 09 24 git-delete-last-commit

User · Answer

Lots of complicated and dangerous answers here  but it s actually easy   git revert --no-commit 0766c053  HEAD git commit   This will revert everything from the HEAD back to the commit hash  meaning it will recreate that commit state in the working tree as if every commit after 0766c053 had been walked back  You can then commit the current tree  and it will create a brand new commit essentially equivalent to the commit you  reverted  to      The --no-commit flag lets git revert all the commits at once- otherwise you ll be prompted for a message for each commit in the range  littering your history with unnecessary new commits    This is a safe and easy way to rollback to a previous state  No history is destroyed  so it can be used for commits that have already been made public

User · Answer

You can complete all these initial steps yourself and push back to the Git repository    Pull the latest version of your repository from Bitbucket using the git pull --all command  Run the Git log command with -n 4 from your terminal  The number after the -n determines the number of commits in the log starting from the most recent commit in your local history     git log -n 4  Reset the head of your repository s history using the git reset --hard HEAD N where N is the number of commits you want to take the head back  In the following example the head would be set back one commit  to the last commit in the repository history  Push the change to Git repository using git push --force to force push the change    If you want the Git repository to a previous commit   git pull --all git reset --hard HEAD 1 git push --force

User · Answer

Assuming you re talking about master and on that respective branch  that said  this could be any working branch you re concerned with      Reset local master branch to November 3rd commit ID git reset --hard 0d1d7fc32e5a947fbd92ee598033d85bfc445a50    Reset remote master branch to November 3rd commit ID git push -f origin 0d1d7fc32e5a947fbd92ee598033d85bfc445a50 master   I found the answer from in a blog post  now no longer exists   Note that this is Resetting and Forcing the change to the remote  so that if others on your team have already git pulled  you will cause problems for them  You are destroying the change history  which is an important reason why people use git in the first place   Better to use revert  see other answers  than reset   If you re a one man team then it probably doesn t matter

User · Answer

Rogue Coder   Working on your own and just want it to work  Follow these instructions below  they   ve worked reliably for me and many others for years   Working with others  Git is complicated  Read the comments below this answer before you do something rash   Reverting Working Copy to Most Recent Commit  To revert to a previous commit  ignoring any changes   git reset --hard HEAD   where HEAD is the last commit in your current branch  Reverting The Working Copy to an Older Commit  To revert to a commit that s older than the most recent commit     Resets index to former commit  replace  56e05fced  with your commit code git reset 56e05fced     Moves pointer back to previous HEAD git reset --soft HEAD  1   git commit -m  Revert to 56e05fced     Updates working copy to reflect the new commit git reset --hard   Credits go to a similar Stack Overflow question  Revert to a commit by a SHA hash in Git

User · Answer

To completely clean a coder s directory up from some accidental changes  we used   git add -A   git reset --hard HEAD   Just git reset --hard HEAD will get rid of modifications  but it won t get rid of  new  files  In their case they d accidentally dragged an important folder somewhere random  and all those files were being treated as new by Git  so a reset --hard didn t fix it  By running the git add -A   beforehand  it explicitly tracked them all with git  to be wiped out by the reset

User · Answer

There is a command  not a part of core Git  but it is in the git-extras package  specifically for reverting and staging old commits   git back   Per the man page  it can also be used as such     Remove the latest three commits git back 3

User · Answer

Revert is the command to rollback the commits   git revert  lt commit1 gt   lt commit2 gt     Sample   git revert 2h3h23233  It is capable of taking range from the HEAD like below  Here 1 says  revert last commit    git revert HEAD 1  HEAD  and then do git push

User · Answer

Yet another simplest solution  you have to change branch to do this  but afterwards you can just run   git branch -f  lt  lt branchname gt  gt  0d1d7fc32e5a947fbd92ee598033d85bfc445a50

User · Answer

As your commits are pushed remotely  you need to remove them  Let me assume your branch is develop and it is pushed over origin   You first need to remove develop from origin   git push origin  develop  note the colon    Then you need to get develop to the status you want  let me assume the commit hash is EFGHIJK   git reset --hard EFGHIJK   Lastly  push develop again   git push origin develop

User · Answer

If you want to correct some error in the last commit a good alternative would be using git commit --amend command  If the last commit is not pointed by any reference  this will do the trick  as it create a commit with the same parent as the last commit  If there is no reference to the last commit  it will simply be discarded and this commit will be the last commit  This is a good way of correcting commits without reverting commits  However it has its own limitations

User · Answer

OK  going back to a previous commit in Git is quite easy     Revert back without keeping the changes   git reset --hard  lt commit gt    Revert back with keeping the changes   git reset --soft  lt commit gt    Explanation  using git reset  you can reset to a specific state  It s common using it with a commit hash as you see above   But as you see the difference is using the two flags --soft and --hard  by default git reset using --soft flag  but it s a good practice always using the flag  I explain each flag     --soft  The default flag as explained  not need to provide it  does not change the working tree  but it adds all changed files ready to commit  so you go back to the commit status which changes to files get unstaged     --hard  Be careful with this flag  It resets the working tree and all changes to tracked files and all will be gone     I also created the image below that may happen in a real life working with Git

User · Answer

To keep the changes from the previous commit to HEAD and move to the previous commit  do   git reset  lt SHA gt    If changes are not required from the previous commit to HEAD and just discard all changes  do   git reset --hard  lt SHA gt

User · Answer

Resetting Staged Changes and Commits  The git reset command lets you change the HEAD- the latest commit your working tree points to - of your repository  It modifies either the staging area or the staging area and working tree   Git s ability to craft commits exactly like you want means that you sometimes need to undo changes to the changes you staged with git add  You can do that by calling git reset HEAD  lt file to change gt    You have two options to get rid of changes completely  git checkout HEAD  lt file s  or path s  gt  is a quick way to undo changes to your staging area and working tree  Be careful with this command  however  because it removes all changes to your working tree   Git doesn t know about those changes since they ve never been committed  There s no way to get those changes back once you run this command   Another command at your disposal is git reset --hard  It is equally destructive to your working tree - any uncommitted changes or staged changes are lost after running it  Running git reset -hard HEAD does the same thing as git checkout HEAD  It just doesn t require a file or path to work   You can use --soft with git reset  It resets the repository to the commit you specify and stages all of those changes  Any changes you have already staged are not affected  nor are the changes in your working tree   Finally  you can use --mixed  to reset the working tree without staging any changes  This also unstages any changes that are staged   Reverting Commits  Sometimes we make mistakes  A commit that wasn t supposed to be shared gets pushed to a public repository  a commit has a bug that can t be fixed and needs to be undone  or maybe you just don t need that code any longer   These cases all call for git revert  The git revert command does just what you might expect  It reverts a single commit by applying a reverse commit to the history   Sometimes you need to revert several commits to completely undo a change  You can use -no-commit  or you can use -n to tell Git to perform the revert  but stop short of committing the change   This lets you combine all the revert commits into one commit  which is useful if you need to revert a feature that spans several commits  Make sure that you revert commits in reverse order-the newest commit first    Otherwise  you might confuse Git by trying to revert code that doesn t exist yet

User · Answer

The best way is  git reset --hard  lt commidId gt   amp  amp  git push --force  This will reset the branch to the specific commit and then will upload the remote server with the same commits as you have in local  Be careful with the --force flag as it removes all the subsequent commits after the selected commit without the option to recover them

User · Answer

There are many answers that provide removing the last commit  However  here is asked how to remove specific commits  and in this case it is to remove the last three commits  to go back to commit on November 3   You can do this with rebase  Simply do   git rebase -i HEAD 4   This will list your last four commits   Now you have the option to remove commits  You do that with drop text    Simply hit i on your keyboard and next to commits you want to remove write drop instead of default pick On the keyboard  hit exit and  wq   To make sure that commits are removed  write   git log   You will see that commits you saved as drop are removed   To push those changes to your remote branch  write   git push --force

User · Answer

git reflog   Choose the number of the HEAD s  of git reflog  where you want revert to and do  for this example I choose the 12    git reset HEAD  12  --hard

User · Answer

If you want to temporarily revert changes because   someone committed code that is breaking the build or breaking the functionality you re working on   You can search for the last working commit using git log and then run   git rebase --onto  lt commitId gt    When the remote branch is working again  you can  git pull --rebase   This method is better than git checkout for temporary changes  because you re not in a detached state

User · Answer

I couldn t revert mine manually for some reason so here is how I ended up doing it    Checked out the branch I wanted to have  copied it  Checked out the latest branch  Copied the contents from the branch I wanted to the latest branch s directory overwriting the changes and committing that

User · Answer

Try resetting to the desired commit -  git reset  lt COMMIT ID gt    to check COMMIT ID use git log   This will reset all changed files to un-added state   Now you can checkout all un-added files by   git checkout    Check git log to verify your changes   UPDATE  If you have one and only commit in your repo  try  git update-ref -d HEAD

User · Answer

The least complicated way I have found to revert a branch to any particular commit  where you can t change the history  is to    Check out the commit or branch your wish to revert from  Edit  git HEAD and change the ref to the branch you which to revert to    Such as   echo  ref  refs heads example   gt   git HEAD   If you then do git status  you should see all the changes between the branch you re on and the one you wish to revert to   If everything looks good  you can commit  You can also use git diff revert  example to ensure that it s the same

User · Answer

Say you have the following commits in a text file named   commits-to-revert txt  I used git log --pretty oneline to get them   fe60adeba6436ed8f4cc5f5c0b20df7ac9d93219 0c27ecfdab3cbb08a448659aa61764ad80533a1b f85007f35a23a7f29fa14b3b47c8b2ef3803d542 e9ec660ba9c06317888f901e3a5ad833d4963283 6a80768d44ccc2107ce410c4e28c7147b382cd8f 9cf6c21f5adfac3732c76c1194bbe6a330fb83e3 fff2336bf8690fbfb2b4890a96549dc58bf548a5 1f7082f3f52880cb49bc37c40531fc478823b4f5 e9b317d36a9d1db88bd34831a32de327244df36a f6ea0e7208cf22fba17952fb162a01afb26de806 137a681351037a2204f088a8d8f0db6e1f9179ca   Create a Bash shell script to revert each of them      bin bash cd  path to working copy for i in  cat   commits-to-revert txt  do     git revert  i --no-commit done   This reverts everything back to the previous state  including file and directory creations  and deletions  commit it to your branch and you retain the history  but you have it reverted back to the same file structure  Why Git doesn t have a git revert --to  lt hash gt  is beyond me

[git] How do I revert a Git repository to a previous commit?

Examples related to git

Examples related to git-checkout

Examples related to git-reset

Examples related to git-revert